Method and apparatus for characterizing performance of a laser, light source design method and system

Abstract

A kind of laser performance characterization method and device, light source design method and system, the laser performance characterization method of the present application is based on the complete base group, the complete mode composition of the laser to be characterized is obtained by optical field fitting operation, and the excitation mode composition of the laser to be characterized is obtained according to the complete mode composition, the excitation mode composition includes: excitation mode group and excitation weight group, the excitation mode group includes multiple excitation modes, and the excitation weight group includes multiple excitation weight factors, and the excitation weight factor corresponds to the excitation mode one by one.Therefore, the technical scheme can obtain the mode number, order and relative intensity information of the laser to be characterized under working condition, so different designs can be effectively evaluated from the perspective of mode, and it has strong guiding significance for the further design optimization of the optical performance of device.

Description

Technical Field

[0001] This invention relates to the field of lasers, and in particular to a method and apparatus for characterizing laser performance, and a method and apparatus for designing light sources. Background Technology

[0002] Beam divergence refers to the degree to which the beam diameter or radius increases with increasing distance from the emission point, and is usually scaled by the divergence angle (e.g., ...). Figure 1 (As shown in the diverging half-angle).

[0003] The far-field divergence angle of a laser is an important performance indicator, and different applications have different requirements for the divergence angle. Lasers used in consumer electronics (such as Face ID) typically require a relatively large far-field divergence angle to ensure that the light intensity is distributed as evenly as possible within the beam diameter, which is beneficial for human eye safety. On the other hand, applications such as optical communication and laser ranging require a smaller far-field divergence angle to concentrate the beam energy at the center, which is beneficial for increasing the transmission distance.

[0004] In laser design, different types of beams can be obtained by adjusting the various modes. However, in experiments and tests, only the peak distribution of the spectrum can be obtained through spectral measurements. This allows us to determine whether the laser is exciting a single mode or multiple modes, and to compare the number of excited modes, but it cannot determine which mode(s) are being excited.

[0005] The operating modes of semiconductor lasers are quite complex. Most semiconductor lasers operate in a multimode state: the far-field divergence angle or beam quality varies depending on the excitation mode. Laser mode excitation is a highly complex physical process, related not only to the geometry of the resonant cavity but also to factors such as carrier concentration, carrier diffusion, current injection distribution, temperature distribution, and gain distribution. Therefore, it is difficult to predict the mode excitation during the laser's operating state during the design phase; experimental evaluation of the excitation information is necessary.

[0006] Measuring the optical power distribution at different spatial angles in the far field allows us to obtain the far-field energy distribution and divergence angle of the laser. An ideal Gaussian beam intensity distribution is as follows: Figure 2 As shown, with I max If the peak light intensity is represented, then the light intensity is 1 / e. 2 The beam radius ω at that point corresponds to half of the divergence angle (half angle).

[0007] However, this only measures the divergence angle and cannot reveal the internal excitation patterns of the laser, thus failing to accurately characterize its optical performance. For example, in radar applications, lasers require increased emission power, necessitating a larger emission aperture. This leads to an increase in the number of excited modes, resulting in a larger divergence angle. Furthermore, varying intensity proportions among the excited modes also contribute to different divergence angles. Measuring only the divergence angle is insufficient to guide optimal laser design. Summary of the Invention

[0008] The problem solved by this invention is that it is difficult to effectively evaluate the optical performance of a device because it is impossible to obtain the excitation mode of the laser.

[0009] To address the above problems, this invention provides a method for characterizing laser performance, comprising:

[0010] The process involves: obtaining the actual light field distribution of the laser to be characterized at a preset position; obtaining a complete substrate set based on the laser to be characterized, the complete substrate set including multiple complete mode substrates; performing a light field fitting operation on the light field of the laser to be characterized at the preset position based on the complete substrate set and the actual light field distribution; obtaining a complete mode composition of the laser to be characterized at the end of the light field fitting operation, the complete mode composition including a complete mode group and a complete weighted group, the complete mode group including multiple complete modes, the complete weighted group including multiple complete weight factors, and the complete mode and the complete weight factors corresponding one-to-one; and obtaining the excitation mode composition of the laser to be characterized based on the complete mode composition, the excitation mode composition including an excitation mode group and an excitation weighted group, the excitation mode group including multiple excitation modes, the excitation weighted group including multiple excitation weight factors, and the excitation weight factors corresponding one-to-one with the excitation modes.

[0011] Optionally, the light field fitting operation includes: setting a weighted reassembly corresponding to a basis set, wherein the basis set includes multiple mode basis sets, the weighted reassembly includes multiple weight factors, and the weight factors correspond one-to-one with the mode basis sets; obtaining a theoretical light field distribution by weighted superposition of the basis set and the weighted reassembly; comparing the difference between the theoretical light field distribution and the actual light field distribution to obtain an error coefficient; determining whether the error coefficient is less than or equal to a preset error threshold; when the error coefficient is less than or equal to the error threshold, the light field fitting operation is completed, and a mode composition is obtained, wherein the mode composition includes weight factors and modes corresponding to the weight factors, and the weight factors correspond one-to-one with the modes; when the error coefficient is greater than the error threshold, adjusting the size of the weight factors to obtain an adjusted weighted reassembly to reduce the difference between the error coefficient and the error threshold; based on the basis set and the adjusted weighted reassembly, re-executing the steps of obtaining the theoretical light field distribution and the comparison step until the error coefficient is less than or equal to the error threshold, the light field fitting operation is completed, and a mode composition is obtained.

[0012] Optionally, the step of obtaining the excitation mode composition of the laser to be characterized based on the complete mode composition of the laser to be characterized includes: using the complete mode composition as the excitation mode composition.

[0013] Optionally, the step of obtaining the excitation mode composition of the laser to be characterized based on the complete mode composition includes: obtaining a dominant basis set based on the complete mode composition and a preset dominant weight threshold, wherein the dominant basis set includes multiple dominant mode bases; performing the light field fitting operation again on the light field formed by the laser to be characterized at a preset position based on the dominant basis set; obtaining the dominant mode composition of the laser to be characterized when the light field fitting operation ends, wherein the dominant mode composition includes a dominant weight factor and a dominant mode corresponding to the dominant weight factor, wherein the dominant weight factor and the dominant mode correspond one-to-one; and using the dominant mode composition as the excitation mode composition.

[0014] Optionally, the step of obtaining the dominant basis set includes: obtaining a reference complete weight factor based on the complete pattern composition; obtaining the ratio of any complete weight factor to the reference complete weight factor; comparing the relative size of the ratio with the dominant weight threshold; and when the ratio is greater than or equal to the dominant weight threshold, the complete pattern corresponding to the complete weight factor is a dominant pattern basis in the dominant basis set.

[0015] Optionally, in the step of obtaining the actual light field distribution formed by the laser to be characterized at a preset position, the preset position includes at least one of a far-field position and a near-field position.

[0016] Optionally, the step of obtaining a complete substrate set includes: obtaining the complete substrate set according to the equivalent fiber model.

[0017] Optionally, the step of obtaining the complete substrate set includes: obtaining the equivalent refractive index based on the material of the laser to be characterized; obtaining the equivalent size based on the structure of the laser to be characterized; establishing an equivalent fiber model based on the equivalent refractive index and the equivalent size; obtaining the waveguide modes transmitted in the equivalent fiber model based on the equivalent fiber model; and obtaining a complete mode substrate based on the waveguide modes to obtain a complete substrate set.

[0018] Optionally, in the step of obtaining a complete base set, all complete pattern bases are transverse patterns.

[0019] Optionally, the step of obtaining the error coefficients includes: obtaining the error coefficients based on the mean square error.

[0020] Optionally, the mean square error is the integral of the light intensity in the cross section perpendicular to the propagation direction at the preset position.

[0021] Optionally, the steps for adjusting the weight factors include: adjusting the weight factors based on a global optimization algorithm to obtain the adjusted weight factors.

[0022] Optionally, the laser to be characterized is a vertical-cavity surface-emitting laser.

[0023] Furthermore, the present invention also provides a light source design method, comprising:

[0024] A laser is provided; the laser is characterized using the characterization method of the present invention to obtain the excitation mode composition of the laser; and a light source is designed based on the excitation mode composition.

[0025] Optionally, the steps of designing the light source include: optimizing the parameters of the laser based on the excitation mode composition.

[0026] Optionally, the light source further includes a collimating optical element; the step of designing the light source further includes designing the collimating optical element based on the excitation mode composition.

[0027] Optionally, the collimating optical element includes a microlens.

[0028] Accordingly, the present invention also provides a laser performance characterization device, specifically comprising:

[0029] The system comprises: an actual light field module, suitable for obtaining the actual light field distribution of the light field formed by the laser to be characterized at a preset position; a complete substrate module, suitable for obtaining a complete substrate set based on the laser to be characterized, the complete substrate set including multiple complete mode substrates; and a light field fitting module, suitable for performing a light field fitting operation on the light field formed by the laser to be characterized at the preset position based on the complete substrate set and the actual light field distribution, and obtaining a complete mode composition of the laser to be characterized upon completion of the light field fitting operation. The composition includes a complete mode group and a complete weighted recombination. The complete mode group includes multiple complete modes, and the complete weighted recombination includes multiple complete weight factors. The complete modes and complete weight factors correspond one-to-one. An excitation mode module is used to obtain the excitation mode composition of the laser to be characterized based on the complete mode composition. The excitation mode composition includes an excitation mode group and an excitation weighted recombination. The excitation mode group includes multiple excitation modes, and the excitation weighted recombination includes multiple excitation weight factors. The excitation weight factors and excitation modes correspond one-to-one.

[0030] Optionally, the light field fitting module includes: a weighting unit, which is adapted to set weighted reassemblies corresponding to the basis set, the basis set including multiple mode basis sets, the weighted reassemblies including multiple weight factors, and the weight factors corresponding one-to-one with the mode basis sets; a superposition unit, which is adapted to obtain a theoretical light field distribution based on the weighted superposition of the basis set and the weight set; an error unit, which is adapted to compare the difference between the theoretical light field distribution and the actual light field distribution to obtain an error coefficient; a comparison unit, which is adapted to compare the relative magnitude of the error coefficient with a preset error threshold; and a mode unit, where the error coefficient is less than or equal to the error threshold, and the mode unit... The unit is suitable for obtaining a pattern composition, which includes weighting factors and patterns corresponding to the weighting factors, with each weighting factor corresponding to a pattern in a one-to-one manner. An adjustment unit is used to adjust the weighting factors when the error coefficient is greater than the error threshold, obtaining an adjusted weighted set to reduce the difference between the error coefficient and the error threshold. The weighting unit resets the weighted set corresponding to the basis set based on the adjusted weighted set. The superposition unit, the error unit, and the comparison unit re-execute the steps of obtaining the theoretical light field distribution, obtaining the error coefficient, and the comparison, respectively, until the error coefficient is less than or equal to the error threshold. The pattern unit then obtains the pattern composition.

[0031] Optionally, the excitation mode module is suitable to be composed of the complete mode as the excitation mode composition.

[0032] Optionally, the excitation mode module is adapted to obtain a dominant basis set based on the complete mode composition and a preset dominant weight threshold, wherein the dominant basis set includes multiple dominant mode bases; the optical field fitting module is further adapted to perform the optical field fitting operation again on the optical field formed by the laser to be characterized at a preset position based on the dominant basis set, and when the optical field fitting operation ends, the dominant mode composition of the laser to be characterized is obtained, wherein the dominant mode composition includes a dominant weight factor and a dominant mode corresponding to the dominant weight factor, wherein the dominant weight factor and the dominant mode correspond one-to-one; the excitation mode module is further adapted to use the dominant mode composition as the excitation mode composition.

[0033] Optionally, the excitation mode module includes: a reference unit, which is adapted to obtain a reference complete weight factor based on the complete mode composition; a ratio unit, which is adapted to obtain the ratio of any complete weight factor to the reference complete weight factor; a comparison ratio unit, which is adapted to compare the relative size of the ratio with the dominant weight threshold; and a collection unit, which stores the complete mode corresponding to the complete weight factor as a dominant mode base in the dominant base set when the ratio is greater than or equal to the dominant weight threshold.

[0034] Optionally, the preset position includes at least one of a far-field position and a near-field position.

[0035] Optionally, the complete substrate module is suitable for obtaining the complete substrate set based on the equivalent fiber model.

[0036] Optionally, the complete substrate module includes: a modeling unit, which is adapted to obtain the equivalent refractive index based on the material of the laser to be characterized, and to obtain the equivalent size based on the structure of the laser to be characterized; the modeling unit is also adapted to establish an equivalent fiber model based on the equivalent refractive index and the equivalent size; and a substrate unit, which is adapted to obtain the waveguide modes transmitted in the equivalent fiber model based on the equivalent fiber model; and to obtain the complete mode substrate based on the waveguide modes transmitted in the equivalent fiber model, so as to obtain a complete substrate set.

[0037] Optionally, all complete pattern bases are horizontal molds.

[0038] Optionally, the error unit obtains the error coefficients based on the mean square error.

[0039] Optionally, the mean square error is the integral of the light intensity in the cross section perpendicular to the propagation direction at the preset position.

[0040] Optionally, the adjustment unit adjusts the weight factors based on a global optimization algorithm to obtain the adjusted weight factors.

[0041] Optionally, the laser to be characterized is a vertical-cavity surface-emitting laser.

[0042] Compared with the prior art, the technical solution of the present invention has the following advantages:

[0043] The technical solution of this invention, based on a complete substrate set, obtains the complete mode composition of the laser to be characterized through optical field fitting. Then, based on the complete mode composition, the excitation mode composition of the laser to be characterized is obtained. The excitation mode composition includes an excitation mode group and an excitation weighting group. The excitation mode group includes multiple excitation modes, and the excitation weighting group includes multiple excitation weighting factors, each corresponding one-to-one with a given excitation mode. Therefore, this technical solution can obtain information on the number, order, and relative intensity of modes excited by the laser to be characterized in its operating state. This allows for effective evaluation of different designs from a mode perspective, providing strong guidance for further design optimization of the device's optical performance.

[0044] In an optional embodiment of the present invention, after obtaining the complete mode composition of the laser to be characterized, the step of obtaining the excitation mode composition of the laser to be characterized includes: obtaining a dominant basis set based on the complete mode composition and a preset dominant weight threshold; performing the light field fitting operation again on the light field formed by the laser to be characterized at a preset position based on the dominant basis set; obtaining the dominant mode composition of the laser to be characterized when the light field fitting operation ends; and using the dominant mode composition as the excitation mode composition. This secondary fitting approach further highlights the most important excitation modes, which helps to eliminate experimental errors and reduces the computational requirements for subsequent design. Attached Figure Description

[0045] Figure 1 This is a schematic diagram of the beam divergence angle;

[0046] Figure 2 This is a schematic diagram of the intensity distribution of an ideal Gaussian beam within a cross section perpendicular to the optical axis;

[0047] Figure 3 This is a schematic flowchart of an embodiment of the laser performance characterization method of the present invention;

[0048] Figure 4 yes Figure 3 A flowchart illustrating the steps for obtaining a complete basis set in the characterization method embodiment shown;

[0049] Figure 5 This is a schematic diagram of the light field distribution of different transverse modes of Laguerre-Gaussian light;

[0050] Figure 6 yes Figure 3 A flowchart illustrating the steps of the light field fitting operation in the embodiment of the characterization method shown.

[0051] Figure 7 This is a schematic diagram of a three-dimensional spherical coordinate system;

[0052] Figure 8 This is a schematic diagram of a two-dimensional polar coordinate system;

[0053] Figure 9 yes Figure 3 The flowchart illustrating the steps for obtaining the excitation mode composition in the characterization method embodiment shown is as follows;

[0054] Figure 10 yes Figure 9 The flowchart of the step of obtaining the dominant mode base in the process of obtaining the excitation mode composition step in the embodiment of the characterization method shown is as follows:

[0055] Figure 11 yes Figure 3 In the embodiment of the characterization method shown, at the near-field position, when the optical field fitting operation is completed based on the complete basis set and based on the dominant basis set respectively, the theoretical optical field distribution and the actual optical field distribution are compared.

[0056] Figure 12 yes Figure 3 In the illustrated representation method embodiment, at the far-field location, when optical field fitting operations are completed based on the complete basis set and based on the dominant basis set respectively, the theoretical optical field distribution and the actual optical field distribution are compared.

[0057] Figure 13 In another embodiment of the laser performance characterization method of the present invention, a comparison of the theoretical optical field distribution and the actual optical field distribution is made when optical field fitting operations are performed based on a complete substrate set and based on a dominant substrate set at a far-field position.

[0058] Figure 14 In another embodiment of the laser performance characterization method of the present invention, the theoretical optical field distribution at the near-field position is obtained when optical field fitting operations are completed based on the complete substrate set and the dominant substrate set, respectively.

[0059] Figure 15 This is a flowchart illustrating an embodiment of the light source design method of the present invention;

[0060] Figure 16 This is a functional block diagram of an embodiment of the laser performance characterization device of the present invention;

[0061] Figure 17 yes Figure 16The functional block diagram of the complete substrate module in the embodiment of the laser performance characterization device shown;

[0062] Figure 18 yes Figure 16 The functional block diagram of the optical field fitting module in the embodiment of the laser performance characterization device shown;

[0063] Figure 19 yes Figure 16 The diagram shows the functional block diagram of the excitation mode module in the embodiment of the laser performance characterization device. Detailed Implementation

[0064] As can be seen from the background technology, the existing methods for characterizing laser performance can only obtain the angle value of the divergence angle, but cannot obtain the excitation mode of the laser. Therefore, it is difficult to conduct more effective evaluation of device design and it is not conducive to subsequent device optimization.

[0065] To address the aforementioned technical problem, the present invention provides a method for characterizing laser performance, comprising:

[0066] The process involves: obtaining the actual light field distribution of the laser to be characterized at a preset position; obtaining a complete substrate set based on the laser to be characterized, the complete substrate set including multiple complete mode substrates; performing a light field fitting operation on the light field of the laser to be characterized at the preset position based on the complete substrate set and the actual light field distribution; obtaining a complete mode composition of the laser to be characterized at the end of the light field fitting operation, the complete mode composition including a complete mode group and a complete weighted group, the complete mode group including multiple complete modes, the complete weighted group including multiple complete weight factors, and the complete mode and the complete weight factors corresponding one-to-one; and obtaining the excitation mode composition of the laser to be characterized based on the complete mode composition, the excitation mode composition including an excitation mode group and an excitation weighted group, the excitation mode group including multiple excitation modes, the excitation weighted group including multiple excitation weight factors, and the excitation weight factors corresponding one-to-one with the excitation modes.

[0067] The technical solution of this invention, based on a complete substrate set, obtains the complete mode composition of the laser to be characterized through optical field fitting. Then, based on the complete mode composition, the excitation mode composition of the laser to be characterized is obtained. The excitation mode composition includes an excitation mode group and an excitation weighting group. The excitation mode group includes multiple excitation modes, and the excitation weighting group includes multiple excitation weighting factors, each corresponding one-to-one with a given excitation mode. Therefore, this technical solution can obtain information on the number, order, and relative intensity of modes excited by the laser to be characterized in its operating state. This allows for effective evaluation of different designs from a mode perspective, providing strong guidance for further design optimization of the device's optical performance.

[0068] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0069] refer to Figure 3 The diagram shows a flowchart of an embodiment of the laser performance characterization method of the present invention.

[0070] The laser performance characterization method includes: step S110, obtaining the actual light field distribution of the light field formed by the laser to be characterized at a preset position; step S120, obtaining a complete substrate set based on the laser to be characterized, the complete substrate set including multiple complete mode substrates; step S130, performing a light field fitting operation on the light field formed by the laser to be characterized at the preset position based on the complete substrate set, and obtaining a complete mode composition of the laser to be characterized at the end of the light field fitting operation, the complete mode composition including a complete mode group and a complete weighted reassembly, the complete mode group including multiple complete modes, the complete weighted reassembly including multiple complete weight factors, the complete mode and the complete weight factors corresponding one-to-one; step S140, obtaining the excitation mode composition of the laser to be characterized based on the complete mode composition of the laser to be characterized, the excitation mode composition including an excitation mode group and an excitation weighted reassembly, the excitation mode group including multiple excitation modes, the excitation weighted reassembly including multiple excitation weight factors, the excitation weight factors and the excitation mode corresponding one-to-one.

[0071] The characterization method can obtain information on the number, order, and relative intensity of modes excited by the laser under operating conditions. Therefore, it can effectively evaluate different designs from the perspective of modes and has strong guiding significance for further design optimization of the optical performance of the device.

[0072] The specific technical solution of the laser performance characterization method embodiment is described in detail below with reference to the accompanying drawings.

[0073] It should be noted that in some embodiments of the present invention, the laser to be characterized is a vertical-cavity surface-emitting laser (VCSEL). In other embodiments of the present invention, the characterization method can also be used to characterize other types of multimode lasers, such as edge-emitting lasers (EELs).

[0074] First, step S110 is executed to obtain the actual light field distribution of the light field formed by the laser to be characterized at a preset position.

[0075] The actual light field distribution is used as a comparison standard for obtaining the composition of excitation modes.

[0076] In some embodiments of the present invention, in the step of obtaining the actual light field distribution formed by the laser to be characterized at a preset position, the preset position includes at least one of a far-field position and a near-field position. The far-field position is a position outside the Rayleigh distance; the near-field position is a position within the Rayleigh distance, typically near the beam waist of a Gaussian beam. The Rayleigh distance (or Rayleigh length, Rayleigh range) refers to the distance along the beam's direction of travel from its beam waist to a cross-section with an area twice the area of ​​the beam waist, where the radius of the cross-section is approximately... The waist radius is times that of the waist.

[0077] As mentioned earlier, the composition of the laser's internal excitation modes affects both the near-field and far-field distributions of the light field formed by the laser. The far-field distribution can be used to improve the far-field divergence angle to optimize beam quality, while the near-field distribution can provide reference and guidance for other aspects such as optical path design and optical component design.

[0078] It should be noted that, in some embodiments of the present invention, the actual light field distribution refers to the light intensity at different positions on a cross section perpendicular to the optical axis, as measured experimentally.

[0079] In some embodiments of the present invention, in the step of obtaining the actual light field distribution formed by the laser to be characterized at a preset position, the actual light field distribution formed by the laser to be characterized at the preset position is measured experimentally.

[0080] In this embodiment, the step of obtaining the actual light field distribution includes: experimentally measuring the actual light field distribution at the near-field position and the actual light field distribution at the far-field position formed by the laser to be characterized, that is, extracting the experimentally measured near-field distribution data and far-field distribution data.

[0081] Perform step S120 to obtain a complete substrate set based on the laser to be characterized.

[0082] The complete substrate set is used as an unfolding substrate in the optical field fitting operation to obtain the excitation mode composition.

[0083] In some embodiments of the present invention, the step of obtaining a complete substrate set includes: obtaining the complete substrate set based on the type, material, and structural parameters of the laser to be characterized. Specifically, the design parameters such as the type, material, and structural parameters of the laser to be characterized affect the oscillating modes that can be formed in the resonant cavity of the laser to be characterized. Therefore, the complete substrate set obtained in this way can effectively control the number of complete mode substrates in the complete substrate set while obtaining a set of orthogonal complete substrates.

[0084] In some embodiments of the present invention, the step of obtaining a complete substrate set includes: obtaining the complete substrate set based on an equivalent fiber model. Obtaining the complete substrate set using an equivalent fiber model effectively controls the number of mode substrates in the complete substrate set.

[0085] Reference Figure 4 , showed Figure 3 The flowchart of the step to obtain a complete basis set in the embodiment of the characterization method shown is illustrated.

[0086] Specifically, the steps for obtaining the complete substrate set include: on the one hand, performing step S121 to obtain the equivalent refractive index based on the material of the laser to be characterized; on the other hand, performing step S122 to obtain the equivalent size based on the structure of the laser to be characterized; then, performing step S122 to establish an equivalent fiber model based on the equivalent refractive index and the equivalent size; next, performing step S124 to obtain the waveguide modes transmitted in the equivalent fiber model based on the equivalent fiber model; finally, performing step S125 to obtain the complete mode substrate based on the waveguide modes transmitted in the equivalent fiber model, thereby obtaining the complete substrate set.

[0087] In some embodiments of the present invention, in the step of obtaining a complete substrate set, the complete mode substrates are all transverse modes. In the excitation mode of the laser, transverse modes affect the optical field distribution perpendicular to the laser propagation direction; therefore, the complete mode substrates are all transverse modes.

[0088] In this embodiment, based on the equivalent fiber model, the number of mode substrates included in the complete substrate set can be determined, and the complete substrate set has completeness.

[0089] It should be noted that in some embodiments of the present invention, the laser to be characterized is a vertical-cavity surface-emitting laser (VCSEL). In the plane perpendicular to the laser propagation direction, the light spot formed by the VCSEL is circular. Therefore, the complete mode substrates in the complete substrate group are all Laguerre-Gaussian light modes.

[0090] like Figure 5As shown, the light field distribution of different transverse modes of Laguerre-Gaussian light is not the same. Among them, the light intensity distribution pattern of the fundamental transverse mode (TEM00) of Laguerre-Gaussian light is circular and concentrated, with a very small distribution range. Therefore, the fundamental transverse mode (TEM00) of Laguerre-Gaussian light has the smallest divergence angle, the largest power density, and the largest visible brightness.

[0091] In some embodiments of the present invention, the laser to be characterized is a vertical cavity surface-emitting laser, and the emitting region is square in the plane perpendicular to the laser propagation direction. The complete mode substrates in the complete substrate set are all Hermetic Gaussian modes. The complete substrate set can also be obtained by applying the above method, and then the optical field fitting operation can be performed.

[0092] In a vertical-cavity surface-emitting laser (VCSEL), multiple transverse modes can oscillate simultaneously within the resonant cavity. The actual emitted light is the result of the superposition of the intensities of these multiple transverse modes. During operation, i.e., when the driving current of the VCSEL exceeds the threshold current, the fewer the number and the lower the order of the transverse modes excited within the resonant cavity, the smaller the far-field divergence angle of the resulting beam.

[0093] Continue to refer to Figure 3 After obtaining the actual light field distribution and the complete substrate set, step S130 is executed. Based on the complete substrate set and the actual light field distribution, a light field fitting operation is performed on the light field formed by the laser to be characterized at a preset position. When the light field fitting operation ends, the complete mode composition of the laser to be characterized is obtained.

[0094] An optical field fitting operation is performed to obtain the complete mode composition of the laser to be characterized.

[0095] Specifically, refer to the following: Figure 6 , showed Figure 3 The flowchart of the light field fitting operation steps in the embodiment of the characterization method shown is illustrated.

[0096] Specifically, the light field fitting operation steps include:

[0097] First, step S131 is executed to set the weighted reassembly corresponding to the basis set. The basis set includes multiple mode basis sets, and the weighted reassembly includes multiple weight factors, each corresponding one-to-one with a mode basis set. Then, step S132 is executed to obtain the theoretical light field distribution based on the weighted superposition of the basis set and the weighted reassembly. Next, step S133 is executed to compare the difference between the theoretical light field distribution and the actual light field distribution to obtain the error coefficient. Then, step S134 is executed to determine whether the error coefficient is less than or equal to a preset error threshold. When the error coefficient is less than or equal to the error threshold, step S135 is executed, and the light field fitting operation is completed. A pattern composition is obtained, comprising a weighting factor and a pattern corresponding to the weighting factor, wherein the weighting factor and the pattern are in one-to-one correspondence. When the error coefficient is greater than the error threshold, in step S136, the weighting factor is adjusted to obtain an adjusted weighting set to reduce the difference between the error coefficient and the error threshold. After obtaining the adjusted weighting set, based on the adjusted weighting set and the basis set, the steps of obtaining the theoretical light field distribution in step S132 and comparing in step S133 are repeated until the error coefficient is less than or equal to the error threshold. Then, the light field fitting operation in step S135 is completed to obtain the pattern composition.

[0098] The weighting factor mentioned above is only an energy weighting factor, which is suitable for the proportion of the corresponding mode substrate in the emitted energy of the laser in the formed light field.

[0099] Specifically, in the step of performing light field fitting based on the complete basis set and the actual light field distribution, a complete weighted reassembly corresponding to the complete basis set is set. The complete basis set includes multiple complete mode basis sets, and the complete weighted reassembly includes multiple complete weight factors. The complete weight factors correspond one-to-one with the complete mode basis sets.

[0100] The optical field of the emitted light from the laser to be characterized is the result of the superposition of the intensities of multiple modes that can oscillate simultaneously within the resonant cavity. Therefore, the weighted superposition of the substrate group and the weight group, which theoretically yields the distribution of the optical field, can be used to obtain the theoretical optical field distribution.

[0101] Specifically, in the step of performing light field fitting based on the complete basis set and the actual light field distribution, the theoretical light field distribution is obtained by weighted superposition of the complete basis set and the complete weight set.

[0102] After obtaining the theoretical light field distribution, and combining it with the actual light field distribution, step S133 is executed to compare the difference between the theoretical light field distribution and the actual light field distribution to obtain the error coefficient.

[0103] The error coefficient is used to characterize the difference between the theoretical light field distribution and the actual light field distribution. In some embodiments of the present invention, the step of obtaining the error coefficient includes: obtaining the error coefficient based on the mean square error. Wherein, the mean square error is the integral of the light intensity in a cross-section perpendicular to the propagation direction at the preset position, that is, the mean square error is the integral of the intensity difference over the area on the beam cross-section at the preset position.

[0104] As mentioned above, in this embodiment, the preset position is a far-field position and a near-field position, therefore the error coefficient is:

[0105] E = E FF ×E NF

[0106] Among them, E FF E represents the error coefficient when the preset position is the far-field position. NF This represents the error coefficient when the preset position is the near-field position.

[0107] Specifically, when the preset position is a far-field position, the error coefficient E FF for:

[0108] E FF =∫[i(θ,φ)-i0(θ,φ)] 2 r 2 sin(θ)dθdφ

[0109] Wherein, with the center position of the light-emitting window of the laser to be characterized as the origin, and the optical axis as the z-axis, a [structure / parameter] is established. Figure 7 The spherical coordinate system shown represents the light intensity at position (r,θ,φ) in the theoretical light distribution, I0(θ,φ) represents the light intensity at position (r,θ,φ) in the actual light distribution, r represents the radial distance in the spherical coordinate system, θ represents the zenith angle in the spherical coordinate system, and φ represents the azimuth angle in the spherical coordinate system.

[0110] r is a constant and can be omitted in the calculation to simplify the calculation. Therefore, when the preset position is the far-field position, the error coefficient E FF It can be simplified to a two-dimensional integral:

[0111] E FF =∫[I(θ,φ)-I0(θ,φ)] 2 sin(θ)dθdφ

[0112] Where θ represents the zenith angle in the spherical coordinate system, and φ represents the azimuth angle in the spherical coordinate system.

[0113] At the far-field position, it can generally be considered rotationally symmetric in the azimuth direction. Therefore, when the preset position is the far-field position, the error coefficient EFF This can be simplified to a one-dimensional integral:

[0114] E FF =∫[I(θ)-I0(θ)] 2 sin(θ)dθ

[0115] Where θ represents the zenith angle in the spherical coordinate system.

[0116] The preset position is the near-field position, and the error coefficient E NF For two-dimensional integrals:

[0117] E NF =∫[I(r, θ) - I0(r, θ)] 2 rdrdθ

[0118] Specifically, within a plane parallel to the emission window of the laser to be characterized, a system is established with the center of the emission window as the origin and the radial direction of the emission window as the radial direction. Figure 8 The polar coordinate system shown is (i.e., the plane in which the optical axis is perpendicular to the polar coordinate system), where I(r,θ) represents the light intensity at position (r,θ) in the theoretical light distribution, I0(r,θ) represents the light intensity at position (r,θ) in the actual light distribution, r represents the polar radius in the polar coordinate system, and θ represents the polar angle in the polar coordinate system.

[0119] At the near-field position, it can generally be considered rotationally symmetric in the polar direction. Therefore, when the preset position is the near-field position, the error coefficient E FF This can be simplified to a one-dimensional integral:

[0120] E NF =∫[I(r)-I0(r)] 2 rdr

[0121] Where r represents the polar radius in the polar coordinate system.

[0122] It should be noted that, since the light field intensity was measured in the experiment by obtaining the light power at the probe position through a detection tool, although light power was measured, the area of ​​the probe was fixed and very small during the measurement process. Therefore, the difference between light power and light intensity was only a constant and could be ignored. Thus, it can be assumed that the light intensity measured in the experiment is the actual light field distribution.

[0123] After obtaining the error threshold, such as Figure 6 As shown, step S134 is executed to compare the relative magnitudes of the error coefficient and the error threshold to determine whether the error coefficient is less than or equal to the preset error threshold; when the error coefficient is less than or equal to the error threshold, step S135 is executed, the light field fitting operation is completed, and the pattern composition is obtained.

[0124] Specifically, in the step of performing light field fitting operation based on the complete basis set and the actual light field distribution, when the light field fitting operation is completed, the obtained mode composition is a complete mode composition, wherein the complete mode composition includes: a complete weight factor and a complete mode corresponding to the complete weight factor, and the complete weight factor and the complete mode correspond one-to-one.

[0125] The complete weighting factor obtained by the light field fitting operation is used as the complete weighting factor of the complete mode composition, and the complete mode basis corresponding to the complete weighting factor is used as the complete mode in the complete mode composition, thereby obtaining the complete mode composition.

[0126] When the error coefficient is greater than the error threshold, step S136 is executed to adjust the size of the weighting factor and obtain an adjusted weighting set to reduce the difference between the error coefficient and the error threshold.

[0127] Specifically, in the step of performing light field fitting based on the complete basis set and the actual light field distribution, the size of the complete weight factor is adjusted to obtain the adjusted complete weight set.

[0128] The step of adjusting the weighting factor is to optimize the theoretical light field distribution so that the theoretical light field distribution is closer to the actual light field distribution.

[0129] Specifically, in the step of adjusting the weighting factor, the weighting factor corresponding to each mode basis in the basis set is used as the independent variable, and the weighting factor is optimized by an optimization algorithm to reduce the difference between the error coefficient and the error threshold.

[0130] Therefore, in the step of performing light field fitting based on the complete basis set and the actual light field distribution, the complete weight factor corresponding to each complete mode basis in the complete basis set is used as the independent variable, and the complete weight factor is optimized by an optimization algorithm to reduce the difference between the error coefficient and the error threshold.

[0131] In some embodiments of the present invention, the step of adjusting the weight factors includes: adjusting the weight factors based on a global optimization algorithm to obtain the adjusted weight factors. Theoretically, a global optimization algorithm can guarantee finding the optimal solution or a near-optimal solution, while avoiding convergence to local minima. In this embodiment, the global optimization algorithm used is a genetic algorithm. In other embodiments of the present invention, other global optimization algorithms such as tabu search, particle swarm optimization, and ant colony optimization can also be used.

[0132] After adjusting the weighting factor and obtaining the adjusted weighting factor, repeat the steps S132 to obtain the theoretical light field distribution and S133 to compare until the error coefficient is less than or equal to the error threshold. Then, execute step S135 to complete the light field fitting operation and obtain the mode composition.

[0133] Specifically, in the step of performing the light field fitting operation based on the complete substrate set and the actual light field distribution, the steps of obtaining the theoretical light field distribution and the comparison step are repeated until the error coefficient is less than or equal to the error threshold. At this point, the light field fitting operation is completed and a complete mode composition is obtained.

[0134] Continue to refer to Figure 3 After the optical field fitting operation is completed, step S140 is executed to obtain the excitation mode composition of the laser to be characterized based on the obtained complete mode composition.

[0135] The excitation mode composition is suitable for characterizing the performance of a laser. Specifically, the excitation mode composition includes: an excitation mode group and an excitation weighting recombination. The excitation mode group includes multiple excitation modes, and the excitation weighting recombination includes multiple excitation weighting factors, each of which corresponds one-to-one with an excitation mode.

[0136] Reference Figure 9 , showed Figure 3 The flowchart shown in the embodiment of the characterization method illustrates the steps for obtaining the excitation mode composition.

[0137] The steps for obtaining the excitation mode composition based on the complete mode composition include: executing step S141, obtaining a dominant basis set based on the complete mode composition and a preset dominant weight threshold, wherein the dominant basis set includes multiple dominant mode bases; executing step S142, performing the light field fitting operation again on the light field formed by the laser to be characterized at a preset position based on the dominant basis set, and obtaining the dominant mode composition of the laser to be characterized when the light field fitting operation ends, wherein the dominant mode composition includes a dominant weight factor and a dominant mode corresponding to the dominant weight factor, wherein the dominant weight factor and the dominant mode correspond one-to-one; and executing step S143, using the dominant mode composition as the excitation mode composition.

[0138] Based on the complete pattern composition, the dominant pattern composition is obtained, and the dominant pattern composition is used as the excitation pattern composition. That is, the excitation pattern composition is obtained through quadratic fitting. This approach further highlights the most important excitation pattern, which is beneficial for eliminating experimental errors and reducing the computational power requirements of subsequent designs.

[0139] During the process of obtaining the actual light field distribution in the experiment, there may be various interferences that may affect the obtained actual light field distribution, resulting in some modes in the complete mode composition not existing in the actual light field. The dominant mode basis in the dominant basis group is the complete mode that dominates the complete mode composition.

[0140] Reference Figure 10 , showed Figure 9 The flowchart shown is a schematic diagram of the process of obtaining the dominant mode base step in the process of obtaining the excitation mode composition step in the embodiment of the characterization method.

[0141] Specifically, the steps for obtaining the dominant basis set include: performing step S141a to obtain a reference complete weight factor based on the complete pattern composition; performing step S141b to obtain the ratio of any complete weight factor to the reference complete weight factor; performing step S141c to compare the relative size of the ratio with the dominant weight threshold; and performing step S141d when the ratio is greater than or equal to the dominant weight threshold, wherein the complete pattern corresponding to the complete weight factor is a dominant pattern basis in the dominant basis set.

[0142] The step of obtaining the reference complete weight factor is suitable for obtaining a benchmark; the step of obtaining the ratio of any complete weight factor to the reference complete weight factor is suitable for obtaining the relative multiple relationship between the complete weight factors; the result of comparing with the dominant weight threshold can determine whether the complete pattern corresponding to the complete weight factor is dominant in the composition of complete patterns; when the ratio is greater than or equal to the dominant weight threshold, it is considered that the complete pattern corresponding to the complete weight factor is dominant in the composition of complete patterns and is a dominant pattern base, that is, it is considered that the complete pattern corresponding to the complete weight factor is a dominant pattern base in the dominant base group.

[0143] In some embodiments of the present invention, the reference complete weight factor can be the largest complete weight factor, that is, the step of obtaining the reference complete weight factor includes: obtaining the maximum value of multiple complete weight factors in the complete weighting; and using the maximum value as the reference complete weight factor. The dominant weight threshold is greater than or equal to 1 / 10.

[0144] In other embodiments of the present invention, the dominant basis set can also be obtained based on the number of complete modes in the complete mode composition and the average value of the completeness weight factors. Specifically, the steps for obtaining the dominant basis set include: first, obtaining the average value of the completeness weight factors in the complete mode composition based on the number of complete modes in the complete mode composition, as a reference completeness weight factor; then, comparing the relative size of any completeness weight factor with the average value; when the completeness weight factor is greater than the average value, the complete mode corresponding to the completeness weight factor is a dominant mode basis in the dominant basis set.

[0145] For example, in some embodiments of the present invention, the complete base set contains 9 complete patterns. Therefore, the average value of the complete weight factors obtained in the complete pattern composition is approximately 10%, and the complete patterns corresponding to complete weight factors higher than the average value of 10% are the dominant pattern bases. In other embodiments of the present invention, the complete base set contains 100 complete patterns. Therefore, the average value of the complete weight factors obtained in the complete pattern composition is also reduced, and the average value is approximately 1% to 3%.

[0146] Furthermore, in other embodiments of the present invention, the dominant mode base can also be obtained based on the order-of-magnitude difference between the complete weight factors corresponding to different complete modes in the complete base set. For example, a complete mode whose corresponding weight factor differs from the reference complete weight factor by more than one order of magnitude can be considered as the dominant mode base, that is, the weight factor corresponding to the dominant mode base is considered to differ from the reference complete weight factor by more than one order of magnitude.

[0147] Continue to refer to Figure 9 After obtaining the dominant substrate group, step S142 is executed. Based on the dominant substrate group and combined with the actual light field distribution, the light field formed by the laser to be characterized at the preset position is subjected to light field fitting operation again to obtain the dominant mode composition.

[0148] Specifically, the steps for performing a light field fitting operation based on the dominant basis set and the actual light field distribution include: First, setting a dominant weight recombination corresponding to the dominant basis set, wherein the dominant weight recombination includes multiple dominant weight factors, and the dominant weight factors correspond one-to-one with the dominant mode basis; then, obtaining a theoretical light field distribution by weighted superposition of the dominant basis set and the dominant weight set; next, comparing the difference between the theoretical light field distribution and the actual light field distribution to obtain an error coefficient; then, determining whether the error coefficient is less than or equal to a preset error threshold; when the error coefficient is less than or equal to the error threshold, the light field fitting operation is completed, and the dominant mode composition is obtained; when the error coefficient is greater than the error threshold, adjusting the size of the weight factors to obtain an adjusted dominant weight recombination, thereby reducing the difference between the error coefficient and the error threshold; after obtaining the adjusted dominant weight recombination, based on the adjusted dominant weight recombination and the dominant basis set, re-executing the steps of obtaining the theoretical light field distribution and the comparison step until the error coefficient is less than or equal to the error threshold, and then executing step S135 to complete the light field fitting operation and obtain the dominant mode composition.

[0149] It should be noted that step S142, which involves performing a light field fitting operation based on the dominant substrate group and the actual light field distribution, can refer to the aforementioned step S130, which involves performing a light field fitting operation on the light field formed by the laser to be characterized at a preset position based on the complete substrate group and the actual light field distribution. This invention will not elaborate on this further here.

[0150] Specifically, the dominant weight factor resulting from the light field fitting operation is used as the dominant weight factor of the dominant mode composition, and the dominant mode basis corresponding to the dominant weight factor is used as the dominant mode in the dominant mode composition, thereby obtaining the dominant mode composition. After obtaining the dominant mode composition, step S143 is executed, using the dominant mode composition as the excitation mode composition, that is, the dominant mode in the dominant mode composition is the excitation mode, and the dominant weight factor corresponding to the dominant mode is the excitation weight factor corresponding to the excitation mode.

[0151] Refer to Table 1 and Figure 11 , Figure 12 Table 1 shows Figure 3 The complete power reorganization and dominance reorganization obtained by the illustrated representation method embodiment; Figure 11 It is a comparison of the theoretical and actual light field distributions at the near-field location when light field fitting operations are performed based on the complete basis set and the dominant basis set, respectively. Figure 12 This is a comparison of the theoretical and actual light field distributions at the far-field location, when light field fitting operations are performed based on the complete basis set and the dominant basis set, respectively.

[0152] When performing optical field fitting based on a complete basis set, the complete basis set contains 27 complete mode basis sets. Therefore, upon completion of the optical field fitting operation, the complete mode composition also contains 27 corresponding complete modes. The results of the obtained complete weighting factors are shown in Table 1. The first column represents the numbers of the 27 complete mode basis sets in the complete basis set, which are also the numbers of the complete modes in the complete mode composition. The second column represents the value of the complete weighting factor in the complete mode composition when the optical field fitting operation based on the complete basis set is completed. The third column represents the value of the dominant weighting factor in the dominant mode composition when the optical field fitting operation is completed again based on the dominant basis set.

[0153] Table 1

[0154]

[0155]

[0156] like Figure 11 and Figure 12 As shown, Figure 11 The horizontal axis represents the polar radius in the aforementioned polar coordinate system, with the unit being micrometers (μm). The vertical axis represents the relative light intensity. The solid line represents the actual light field distribution, the dashed line represents the theoretical light field distribution when the light field fitting operation is completed based on the complete substrate set, and the dotted line represents the theoretical light field distribution when the light field fitting operation is completed again based on the dominant substrate set. Figure 12 The horizontal axis represents the zenith angle in the aforementioned spherical coordinate system, in degrees (deg). The solid line represents the actual light field distribution, the dashed line represents the theoretical light field distribution when the light field fitting operation is completed based on the complete basis set, and the dotted line represents the theoretical light field distribution when the light field fitting operation is completed again based on the dominant basis set.

[0157] according to Figure 12 The comparison results show that, based on the actual optical field distribution, the divergence angle of the laser to be characterized at the far-field position is approximately 21.24° (it should be noted that the divergence angle is the integral of the light intensity within this angle range accounting for 86% of the total energy of the cross section); based on the theoretical optical field distribution, the divergence angle of the laser to be characterized at the far-field position is approximately 20.16°. Figure 11 and 13 As can be seen, the theoretical and actual optical field distributions almost completely overlap at both the near-field and far-field positions, and the divergence angles obtained at the far-field position are also very close. Therefore, the mode composition obtained by the method of the present invention can accurately characterize the mode excitation of the laser.

[0158] Furthermore, referring to Table 1, when performing the light field fitting operation based on the complete basis set, the complete basis set contains 27 complete mode basis sets. When the light field fitting operation is completed, the complete mode composition also contains 27 corresponding complete modes. Using the maximum complete weight factor as the reference complete weight factor and 1 / 10 as the dominant weight threshold, the ratio of the complete weight factor to the reference complete weight factor for complete modes numbered 18, 22, 23, and 25 is less than the dominant weight threshold. Therefore, these complete modes do not dominate in the complete mode composition and cannot be used as the dominant mode basis in the dominant basis set. The remaining complete modes are used as dominant mode basis sets to form the dominant basis set, and the light field fitting operation is performed again.

[0159] according to Figure 11 and Figure 12 The comparison results show that, whether at the near-field or far-field position, the theoretical light field distribution obtained by performing a light field fitting operation based on the complete basis set is basically consistent with the theoretical light field distribution obtained by performing a light field fitting operation again based on the dominant basis set.

[0160] It should be noted that in this embodiment, the method of obtaining the dominant mode composition through the complete mode composition and using the dominant mode composition as the excitation mode composition is merely an example. In other embodiments of the present invention, the step of obtaining the excitation mode composition of the laser to be characterized based on the complete mode composition includes: using the complete mode composition as the excitation mode composition, that is, directly using the complete mode in the complete mode composition as the excitation mode, and the complete weight factor corresponding to the complete mode as the excitation weight factor corresponding to the excitation mode.

[0161] In the above embodiments, the preset positions are far-field and near-field positions. That is, in the step of obtaining the actual light field distribution in the characterization method embodiments, the actual light field distribution at the near-field position and the actual light field distribution at the far-field position are obtained respectively; in the step of performing the light field fitting operation, the light field at the near-field position and the light field at the far-field position are respectively subjected to the light field fitting operation to obtain the complete mode composition. However, this approach is only an example. In other embodiments of the present invention, the preset position can also be one of the far-field position and the near-field position.

[0162] Refer to Table 2 and Figure 13 , Figure 14 This paper illustrates the results and comparisons of the optical field fitting operation during the characterization process of another embodiment of the laser performance characterization method of the present invention. Table 2 shows the complete weighted reassembly and dominant weighted reassembly obtained in the embodiment of the characterization method. Figure 13It is a comparison of the theoretical and actual light field distributions at the far-field location when light field fitting operations are performed based on the complete basis set and the dominant basis set, respectively. Figure 14 It is the theoretical light field distribution at the near-field location when light field fitting operations are completed based on the complete basis set and the dominant basis set, respectively.

[0163] In this embodiment, the laser to be characterized is also a vertical-cavity surface-emitting laser, therefore the mode substrate in the obtained complete substrate set is the Laguerre-Gaussian light mode (e.g., Figure 5 (as shown in the image).

[0164] Table 2

[0165]

[0166]

[0167] As shown in Table 2, the laser emission window size in this embodiment is smaller, resulting in fewer complete substrate modes. When performing optical field fitting based on the complete substrate group, which contains 13 complete mode substrates, the optical field fitting operation is completed, and the complete mode composition also contains 13 corresponding complete modes. The obtained complete weighting factor results are shown in Table 2. The first column represents the numbers of the 13 complete mode substrates in the complete substrate group, which are also the numbers of the complete modes in the complete mode composition; the second column represents the value of the complete weighting factor in the complete mode composition when the optical field fitting operation based on the complete substrate group is completed; and the third column represents the value of the dominant weighting factor in the dominant mode composition when the optical field fitting operation is completed again based on the dominant substrate group.

[0168] Reference Figure 13 The horizontal axis represents the zenith angle in the aforementioned spherical coordinate system, in degrees (deg). The solid line represents the actual light field distribution, the dashed line represents the theoretical light field distribution when the light field fitting operation is completed based on the complete basis set, and the dotted line represents the theoretical light field distribution when the light field fitting operation is completed again based on the dominant basis set.

[0169] Based on the actual optical field distribution, the divergence angle of the laser to be characterized at the far field position is approximately 20.64°; based on the theoretical optical field distribution, the divergence angle at the far field position is approximately 21.60°. Furthermore, at the far field position, the theoretical and actual optical field distributions almost completely overlap.

[0170] Referring again to Table 2, when performing light field fitting based on the complete basis set, the complete basis set contains 13 complete mode basis sets. When the light field fitting operation is completed, the complete mode composition also contains 13 corresponding complete modes. Taking the maximum complete weight factor as the reference complete weight factor and 1 / 10 as the dominant weight threshold, the ratio of the complete weight factor to the reference complete weight factor for complete modes numbered 10, 11, 12, and 13 is less than the dominant weight threshold. Therefore, when performing light field fitting based on the dominant basis set, the above-mentioned complete modes are omitted. That is, the remaining complete modes numbered 1-9 are used as dominant mode basis sets to form the dominant basis set, and the light field fitting operation is performed again.

[0171] Reference Figure 14 The horizontal axis represents the polar radius in the aforementioned polar coordinate system, with the unit being micrometers (μm). The vertical axis represents the relative light intensity. The solid line represents the actual light field distribution, the dashed line represents the theoretical light field distribution when the light field fitting operation is completed based on the complete substrate set, and the dotted line represents the theoretical light field distribution when the light field fitting operation is completed again based on the dominant substrate set.

[0172] Based on the theoretical light field distribution obtained from the second fitting, it can be determined that the divergence angle of the laser to be characterized at the far-field position is approximately 21.24°. Figure 13 When the optical field fitting operation is completed based on a complete basis set, the obtained theoretical optical field distribution is closer to the actual optical field distribution than the theoretical optical field distribution. Moreover, at the far field position, the theoretical optical field distribution and the actual optical field distribution almost completely overlap.

[0173] Therefore, it can be seen that the theoretical light field distribution obtained by performing light field fitting operation based on the complete substrate set is basically consistent with the theoretical light field distribution obtained by performing light field fitting operation again based on the dominant substrate set. That is, the composition of the dominant mode is consistent with the theoretical light field distribution reflected by the complete mode set.

[0174] Accordingly, the present invention also provides a light source design method, with reference to Figure 15 The diagram shows a flowchart of an embodiment of the light source design method of the present invention.

[0175] The light source design method includes: step S210, providing a laser; step S220, characterizing the laser using the characterization method of the present invention to obtain the excitation mode composition of the laser; and step S230, designing a light source based on the excitation mode composition.

[0176] The characterization method characterizes the laser to obtain the composition of the excitation modes, that is, to obtain the number, order and relative intensity information of the modes excited by the laser in the working state. Therefore, the laser can be characterized from the perspective of excitation modes, and the optical performance of the laser can be characterized more accurately from the perspective of micro-modes. This is beneficial to further optimize the optical performance of the device and further optimize the performance of the designed light source.

[0177] The steps for designing the light source include adjusting the light source parameters, specifically including: determining the parameter items of the light source to be used, selecting the value range of the parameter items according to the excitation mode composition of the laser, and / or adjusting the values ​​of one or more parameter items.

[0178] In some embodiments of the present invention, the step of designing the light source includes: optimizing the structure of the laser based on the excitation mode composition. The excitation mode composition obtained by the characterization method includes an excitation mode group and an excitation weight group. It can be found that in the mode composition excited by the laser in the working state, the higher-order modes with higher weights are more likely to be excited. By optimizing the laser design, that is, adjusting the laser's structure, materials and other parameters, focusing on reducing the excitation weight of the corresponding higher-order modes, the excitation weight of the fundamental mode is increased, thereby more specifically optimizing the laser performance, improving beam quality and reducing divergence angle.

[0179] In some embodiments of the present invention, the light source further includes a collimating optical element. In light sources employing lasers, particularly vertical-cavity surface-emitting lasers (VCSELs), to reduce the laser divergence angle, one approach is to directly fabricate or encapsulate a collimating optical element on the laser. One collimating optical element corresponds to one emission aperture, directly collimating the light emitted by the laser. Since this collimating optical element is very close to the laser, the resulting light field distribution varies depending on the light mode. Designing the collimating optical element solely for the final beam may lead to deviations in the collimation effect. Therefore, the design of the light source also includes designing the collimating optical element based on the excitation mode composition. Designing the collimating optical element according to the excitation mode composition allows consideration of each excitation mode and its weighting factor, and combined with simulation-designed collimating optical elements, can achieve better collimation results. Specifically, the collimating optical element includes a microlens.

[0180] Accordingly, the present invention also provides a laser performance characterization device.

[0181] refer to Figure 16 The diagram shows a functional block diagram of an embodiment of the laser performance characterization device of the present invention.

[0182] The laser performance characterization device 100 includes:

[0183] The system comprises: an actual light field module 110, adapted to obtain the actual light field distribution of the light field formed by the laser to be characterized at a preset position; a complete substrate module 120, adapted to obtain a complete substrate set based on the laser to be characterized, the complete substrate set including multiple complete mode substrates; and a light field fitting module 130, adapted to perform a light field fitting operation on the light field formed by the laser to be characterized at the preset position based on the complete substrate set and the actual light field distribution, and obtaining the complete mode composition of the laser to be characterized upon completion of the light field fitting operation. The complete mode composition includes a complete mode group and a complete weighted recombination. The complete mode group includes multiple complete modes, and the complete weighted recombination includes multiple complete weight factors. The complete mode and the complete weight factor correspond one-to-one. The excitation mode module 140 is adapted to obtain the excitation mode composition of the laser to be characterized based on the complete mode composition of the laser to be characterized. The excitation mode composition includes an excitation mode group and an excitation weighted recombination. The excitation mode group includes multiple excitation modes, and the excitation weighted recombination includes multiple excitation weight factors. The excitation weight factors correspond one-to-one with the excitation mode.

[0184] The characterization device 100 can obtain information on the number, order, and relative intensity of modes excited by the laser to be characterized in its working state. Therefore, it can effectively evaluate different designs from the perspective of modes, which has strong guiding significance for further design optimization of the optical performance of the device.

[0185] It should be noted that in some embodiments of the present invention, the laser to be characterized is a vertical-cavity surface-emitting laser (VCSEL). In other embodiments of the present invention, the characterization device 100 can also characterize the performance of other types of multimode lasers, such as edge-emitting lasers (EELs).

[0186] The actual light field module 110 is used to obtain the actual light field distribution at a preset position as a comparison standard.

[0187] In some embodiments of the present invention, the preset position includes at least one of a far-field position and a near-field position. The far-field position is a position outside the Rayleigh distance; the near-field position is a position within the Rayleigh distance, typically near the waist of a Gaussian beam. The Rayleigh distance (or Rayleigh length, Rayleigh range) refers to the distance along the beam's direction of travel from its waist to a cross-section with an area twice the area of ​​the waist, where the radius of the cross-section is approximately... The waist radius is times that of the waist.

[0188] As mentioned earlier, the composition of the laser's internal excitation modes affects both the near-field and far-field distributions of the light field formed by the laser. The far-field distribution can be used to improve the far-field divergence angle to optimize beam quality, while the near-field distribution can provide reference and guidance for other aspects such as optical path design and optical component design.

[0189] It should be noted that, in some embodiments of the present invention, the actual light field module 110 experimentally measures the actual light field distribution of the light field formed by the laser to be characterized at a preset position. Specifically, the actual light field module 110 obtains the actual light field distribution by experimentally measuring the light intensity at different positions on a cross section perpendicular to the optical axis.

[0190] In this embodiment, the actual light field module 110 experimentally measures the actual light field distribution at the near-field position and the actual light field distribution at the far-field position formed by the laser to be characterized, that is, extracts the experimentally measured near-field distribution data and far-field distribution data.

[0191] The complete substrate module 120 is used to obtain a complete substrate set based on the laser to be characterized.

[0192] The complete substrate set is used as an unfolding substrate in the optical field fitting operation to obtain the excitation mode composition. Specifically, the complete substrate set includes multiple complete mode substrates.

[0193] In some embodiments of the present invention, the complete substrate module 120 obtains the complete substrate set based on the type, material, and structural parameters of the laser to be characterized. Specifically, the design parameters such as the type, material, and structural parameters of the laser to be characterized affect the oscillating modes that can be formed in the resonant cavity of the laser to be characterized. Therefore, the complete substrate set obtained in this way can effectively control the number of complete mode substrates in the complete substrate set while obtaining a set of orthogonal complete substrates.

[0194] In some embodiments of the present invention, the complete substrate module 120 obtains the complete substrate set based on an equivalent fiber model. Obtaining the complete substrate set using an equivalent fiber model effectively controls the number of complete mode substrates within the complete substrate set.

[0195] Reference Figure 17 , showed Figure 16 The diagram shows the functional block diagram of the complete substrate module in the embodiment of the laser performance characterization device.

[0196] The complete substrate module 120 includes: a modeling unit 122, which is adapted to obtain the equivalent refractive index based on the material of the laser to be characterized, and to obtain the equivalent size based on the structure of the laser to be characterized; the modeling unit is also adapted to establish an equivalent fiber model based on the equivalent refractive index and the equivalent size; and a substrate unit 125, which is adapted to obtain the waveguide modes transmitted in the equivalent fiber model based on the equivalent fiber model; and to obtain the complete mode substrate based on the waveguide modes transmitted in the equivalent fiber model, so as to obtain a complete substrate set.

[0197] In some embodiments of the present invention, the complete mode substrates are all transverse modes. In the excitation mode of the laser, transverse modes affect the optical field distribution perpendicular to the laser propagation direction; therefore, the complete mode substrates are all transverse modes. In this embodiment, based on the equivalent fiber model, the number of mode substrates included in the complete substrate group can be determined, and the complete substrate group possesses completeness.

[0198] It should be noted that in some embodiments of the present invention, the laser to be characterized is a vertical-cavity surface-emitting laser (VCSEL). In the plane perpendicular to the laser propagation direction, the light spot formed by the VCSEL is circular; therefore, the mode substrate in the complete substrate set is a Laguerre-Gaussian light mode.

[0199] like Figure 5 As shown, the light field distribution of different transverse modes of Laguerre-Gaussian light is not the same. Among them, the light intensity distribution pattern of the fundamental transverse mode (TEM00) of Laguerre-Gaussian light is circular and concentrated, with a very small distribution range. Therefore, the fundamental transverse mode (TEM00) of Laguerre-Gaussian light has the smallest divergence angle, the largest power density, and the largest visible brightness.

[0200] In some embodiments of the present invention, the laser to be characterized is a vertical cavity surface-emitting laser, and the emitting region is square in the plane perpendicular to the laser propagation direction. The complete mode substrates in the complete substrate set are all Hermetic Gaussian modes. The complete substrate set can also be obtained by applying the above method, and then the optical field fitting operation can be performed.

[0201] In a vertical-cavity surface-emitting laser (VCSEL), multiple transverse modes can oscillate simultaneously within the resonant cavity. The actual emitted light is the result of the superposition of the intensities of these multiple transverse modes. During operation, i.e., when the driving current of the VCSEL exceeds the threshold current, the fewer the number and the lower the order of the transverse modes excited within the resonant cavity, the smaller the far-field divergence angle of the resulting beam.

[0202] Continue to refer to Figure 16 The characterization device 100 further includes a light field fitting module 130 suitable for performing light field fitting operations to obtain a complete pattern composition. (Refer to reference...) Figure 18 , showed Figure 16 The functional block diagram of the optical field fitting module in the embodiment of the laser performance characterization device shown is illustrated.

[0203] Specifically, the light field fitting module 130 includes: a weighting unit 131, which is adapted to set weighted reassemblies corresponding to the basis set, the basis set including multiple mode basis sets, the weighted reassemblies including multiple weight factors, and the weight factors corresponding one-to-one with the mode basis sets; a superposition unit 132, which is adapted to obtain a theoretical light field distribution based on the weighted superposition of the basis set and the weight set; an error unit 133, which is adapted to compare the difference between the theoretical light field distribution and the actual light field distribution to obtain an error coefficient; a comparison unit 134, which is adapted to compare the relative magnitude of the error coefficient with a preset error threshold; and a mode unit 135, where the error coefficient is less than or equal to the error threshold, and the mode unit 135 is adapted to obtain... The system obtains a pattern composition, which includes weighting factors and patterns corresponding to the weighting factors, with each weighting factor corresponding to a pattern in a one-to-one manner. An adjustment unit 136 adjusts the weighting factors when the error coefficient is greater than the error threshold to obtain an adjusted weighting set, thereby reducing the difference between the error coefficient and the error threshold. After obtaining the adjusted weighting set, the weighting unit 131 resets the weighting set corresponding to the basis set based on the adjusted weighting set. The superposition unit 132, the error unit 133, and the comparison unit 134 re-execute the steps of obtaining the theoretical light field distribution, obtaining the error coefficient, and comparison, respectively, until the error coefficient is less than or equal to the error threshold. The pattern unit 135 then obtains the pattern composition.

[0204] It should be noted that the weighting factor mentioned is only an energy weighting factor, which is suitable for the proportion of the corresponding mode substrate in the emitted energy of the laser in the formed light field.

[0205] Specifically, based on the complete basis set and the actual light field distribution, in the light field fitting module 130, the weighting unit 131 sets a complete weight reassembly corresponding to the complete basis set. The complete basis set includes multiple complete mode basis sets, and the complete weight reassembly includes multiple complete weight factors. The complete weight factors correspond one-to-one with the complete mode basis sets.

[0206] The optical field of the emitted light generated by the laser to be characterized is the result of the superposition of the intensities of multiple modes that can oscillate simultaneously within the resonant cavity. Therefore, the superposition unit 132 can theoretically obtain the distribution of the optical field, that is, obtain the theoretical optical field distribution.

[0207] Specifically, based on the complete substrate set and the actual light field distribution, the superposition unit 132 obtains the theoretical light field distribution by weighted superposition of the complete substrate set and the complete weight set.

[0208] After the superposition unit 132 obtains the theoretical light field distribution, the error unit 133 combines the actual light field distribution to compare the difference between the theoretical light field distribution and the actual light field distribution, and obtains the error coefficient.

[0209] The error coefficient is used to characterize the difference between the theoretical light field distribution and the actual light field distribution. In some embodiments of the present invention, the error unit 133 obtains the error coefficient based on the mean square error. The mean square error is the integral of the light intensity in the cross-section perpendicular to the propagation direction at the preset position; that is, the mean square error is the integral of the intensity difference over the area on the beam cross-section at the preset position.

[0210] As mentioned above, in this embodiment, the preset position is a far-field position and a near-field position, therefore the error coefficient is:

[0211] E = E FF ×e NF

[0212] Among them, E FF E represents the error coefficient when the preset position is the far-field position. NF This represents the error coefficient when the preset position is the near-field position.

[0213] Specifically, when the preset position is a far-field position, the error coefficient E FF for:

[0214] e FF =∫[I(θ,φ)-I0(θ,φ)] 2 r 2 sin(θ)dθdφ

[0215] Here, with the center of the light-emitting window of the laser to be characterized as the origin and the optical axis as the z-axis, a system is established... Figure 7 The spherical coordinate system shown represents the light intensity at position (r,θ,φ) in the theoretical light distribution, I0(θ,φ) represents the light intensity at position (r,θ,φ) in the actual light distribution, r represents the radial distance in the spherical coordinate system, θ represents the zenith angle in the spherical coordinate system, and φ represents the azimuth angle in the spherical coordinate system.

[0216] r is a constant and can be omitted in the calculation to simplify the calculation. Therefore, when the preset position is the far-field position, the error coefficient E FF It can be simplified to a two-dimensional integral:

[0217] E FF=∫[I(θ,φ)-I0(θ,φ)] 2 sin(θ)dθdφ

[0218] Where θ represents the zenith angle in the spherical coordinate system, and φ represents the azimuth angle in the spherical coordinate system.

[0219] At the far-field position, it can generally be considered rotationally symmetric in the azimuth direction. Therefore, when the preset position is the far-field position, the error coefficient E FF This can be simplified to a one-dimensional integral:

[0220] E FF =∫[I(θ)-I0(θ)] 2 sin(θ)dθ

[0221] Where θ represents the zenith angle in the spherical coordinate system.

[0222] The preset position is the near-field position, and the error coefficient E NF For two-dimensional integrals:

[0223] E NF =∫[I(r, θ) - I0(r, θ)] 2 rdrdθ

[0224] Specifically, within a plane parallel to the emission window of the laser to be characterized, a system is established with the center of the emission window as the origin and the radial direction of the emission window as the radial direction. Figure 8 The polar coordinate system shown is (i.e., the plane in which the optical axis is perpendicular to the polar coordinate system). I(r,θ) represents the light intensity at position (r,θ) in the theoretical light distribution, I0(r,θ) represents the light intensity at position (r,θ) in the actual light distribution, r represents the polar radius in the polar coordinate system, and θ represents the polar angle in the polar coordinate system.

[0225] At the near-field position, it can generally be considered rotationally symmetric in the polar direction. Therefore, when the preset position is the near-field position, the error coefficient E FF This can be simplified to a one-dimensional integral:

[0226] E NF =∫[I(r)-I0(r)] 2 rdr

[0227] Where r represents the polar radius in the polar coordinate system.

[0228] It should be noted that, since the light field intensity was measured in the experiment by obtaining the light power at the probe position through a detection tool, although light power was measured, the area of ​​the probe was fixed and very small during the measurement process. Therefore, the difference between light power and light intensity was only a constant and could be ignored. Thus, it can be assumed that the light intensity measured in the experiment is the actual light field distribution.

[0229] Continue to refer to Figure 18 After the error unit 133 obtains the error coefficient, the comparison unit 134 compares the relative size of the error coefficient and the error threshold to determine whether the error coefficient is less than or equal to the preset error threshold; when the error coefficient is less than or equal to the error threshold, the mode unit 135 obtains the mode composition.

[0230] Based on the complete basis set and the actual light field distribution, the mode composition obtained by the mode unit 135 is a complete mode composition. The complete mode composition includes: complete weighting factors and complete modes corresponding to the complete weighting factors, with each complete weighting factor corresponding to a complete mode. Specifically, the complete weighting factors obtained from the light field fitting operation are used as the complete weighting factors of the complete mode composition, and the complete mode basis corresponding to the complete weighting factors are used as the complete modes in the complete mode composition, thereby obtaining the complete mode composition.

[0231] When the error coefficient is greater than the error threshold, such as Figure 18 As shown, the adjustment unit 136 adjusts the magnitude of the weighting factors to obtain an adjusted weighted set, thereby optimizing the theoretical light field distribution and reducing the difference between the error coefficient and the error threshold, so that the theoretical light field distribution is closer to the actual light field distribution. Specifically, based on the complete basis set and the actual light field distribution, the adjustment unit 136 adjusts the magnitude of the complete weighting factors to obtain an adjusted complete weighted set.

[0232] The adjustment unit 136 uses the weight factor corresponding to each mode basis in the basis set as the independent variable, and optimizes the weight factor through an optimization algorithm to reduce the difference between the error coefficient and the error threshold. Specifically, based on the complete basis set and the actual light field distribution, the adjustment unit 136 uses the complete weight factor corresponding to each complete mode basis in the complete basis set as the independent variable, and optimizes the complete weight factor through an optimization algorithm to reduce the difference between the error coefficient and the error threshold.

[0233] In some embodiments of the present invention, the adjustment unit 136 adjusts the weight factors based on a global optimization algorithm to obtain the adjusted weight factors. Theoretically, a global optimization algorithm can guarantee finding the optimal solution or a near-optimal solution, while avoiding convergence to local minima. In this embodiment, the global optimization algorithm used is a genetic algorithm. In other embodiments of the present invention, other global optimization algorithms such as tabu search, particle swarm optimization, and ant colony optimization can also be used.

[0234] After the adjustment unit 136 obtains the adjusted weight factor, the weight unit 131 resets the weight recombination corresponding to the basis group according to the adjusted weight recombination. The superposition unit 132, the error unit 133 and the comparison unit 134 respectively re-execute the above steps of obtaining the theoretical light field distribution, obtaining the error coefficient and comparison, until the error coefficient is less than or equal to the error threshold. The mode unit 135 obtains the mode composition.

[0235] Specifically, after the adjustment unit 136 obtains the adjusted weight factor, the weight unit 131 resets the complete weight recombination corresponding to the complete basis set according to the adjusted complete weight recombination. The superposition unit 132, the error unit 133, and the comparison unit 134 respectively re-execute the above steps of obtaining the theoretical light field distribution, obtaining the error coefficient, and comparison until the error coefficient is less than or equal to the error threshold. The mode unit 135 obtains the complete mode composition.

[0236] Continue to refer to Figure 16 The characterization device 100 further includes an excitation mode module 140, which obtains the excitation mode composition of the laser to be characterized based on the obtained complete mode composition.

[0237] The excitation mode composition is suitable for characterizing the performance of a laser. Specifically, the excitation mode composition includes: an excitation mode group and an excitation weighting recombination. The excitation mode group includes multiple excitation modes, and the excitation weighting recombination includes multiple excitation weighting factors, each of which corresponds one-to-one with an excitation mode.

[0238] like Figure 16As shown, in some embodiments of the present invention, the excitation mode module 140 is adapted to obtain a dominant basis set based on the complete mode composition and a preset dominant weight threshold, wherein the dominant basis set includes multiple dominant mode bases; the optical field fitting module 130 is also adapted to perform the optical field fitting operation again on the optical field formed by the laser to be characterized at a preset position based on the dominant basis set; when the optical field fitting operation ends, the dominant mode composition of the laser to be characterized is obtained; the dominant mode composition includes a dominant weight factor and a dominant mode corresponding to the dominant weight factor; the dominant weight factor and the dominant mode correspond one-to-one; the excitation mode module 140 is also adapted to use the dominant mode composition as the excitation mode composition.

[0239] Based on the complete pattern composition, the dominant pattern composition is obtained, and the dominant pattern composition is used as the excitation pattern composition. That is, the excitation pattern composition is obtained through quadratic fitting. This approach further highlights the most important excitation pattern, which is beneficial for eliminating experimental errors and reducing the computational power requirements of subsequent designs.

[0240] During the process of obtaining the actual light field distribution in the experiment, there may be various interferences that may affect the obtained actual light field distribution, resulting in some complete modes in the complete mode composition not existing in the actual light field. The dominant mode basis in the dominant basis set is the complete mode that dominates the complete mode composition.

[0241] Reference Figure 19 , Figure 16 The diagram shows the functional block diagram of the excitation mode module in the embodiment of the laser performance characterization device.

[0242] The activation mode module 140 includes: a reference unit 141, which is adapted to obtain a reference complete weight factor based on the complete mode composition; a ratio unit 142, which is adapted to obtain the ratio of any complete weight factor to the reference complete weight factor; a comparison ratio unit 143, which is adapted to compare the ratio with the relative size of the dominant weight threshold; and a collection unit 144, which stores the complete mode corresponding to the complete weight factor as a dominant mode base in the dominant base set when the ratio is greater than or equal to the dominant weight threshold.

[0243] The reference unit 141 is used to obtain a benchmark; the ratio unit 142 is used to obtain the relative multiple relationship between the complete weight factors; the comparison ratio unit 143 is used to determine whether the complete pattern corresponding to the complete weight factor is dominant in the composition of complete patterns; when the ratio is greater than or equal to the dominant weight threshold, the collection unit 144 considers that the complete pattern corresponding to the complete weight factor is dominant in the composition of complete patterns and is a dominant pattern basis, that is, considers the complete pattern corresponding to the complete weight factor as a dominant pattern basis in the dominant basis group.

[0244] In some embodiments of the present invention, the reference complete weight factor can be the largest complete weight factor; that is, the reference unit 141 includes an extremum generator, which is used to obtain the maximum value of multiple complete weight factors in the complete weight reassembly; the reference unit 141 uses the maximum value as the reference complete weight factor. The dominant weight threshold is greater than or equal to 10.

[0245] In other embodiments of the present invention, the activation mode module may also obtain the dominant basis set based on the number of complete modes in the complete mode composition and the average value of the complete weight factors. Specifically, the activation mode module includes: a mean unit, which is adapted to obtain the average value of the complete weight factors in the complete mode composition based on the number of complete modes in the complete mode composition, as a reference complete weight factor; a comparison unit, which is adapted to compare the relative size of any complete weight factor with the average value; and a collection unit, which is adapted to store the complete mode corresponding to the complete weight factor as a dominant mode basis in the dominant basis set when the complete weight factor is greater than the average value.

[0246] For example, in some embodiments of the present invention, the complete base set contains 9 complete patterns. Therefore, the average value of the completeness weight factors in the complete pattern composition is approximately 10%, and the complete patterns corresponding to completeness weight factors higher than the average value of 10% are the dominant pattern bases. In other embodiments of the present invention, the complete base set contains 100 complete patterns. Therefore, the average value of the completeness weight factors in the complete pattern composition is also reduced, and the average value is approximately 1% to 3%.

[0247] Furthermore, in other embodiments of the present invention, the excitation mode module 140 may also obtain the dominant mode base based on the order-of-magnitude difference between the complete weight factors corresponding to different complete modes in the complete base set. For example, a complete mode whose corresponding weight factor differs from the reference complete weight factor by more than one order of magnitude can be considered as the dominant mode base, that is, the weight factor corresponding to the dominant mode base is considered to differ from the reference complete weight factor by more than one order of magnitude.

[0248] Continue to refer to Figure 16 The excitation module 140 is also connected to the optical field fitting module 130. After the excitation module 140 obtains the dominant substrate set, the optical field fitting module 130 is also adapted to perform the optical field fitting operation again on the optical field formed by the laser to be characterized at a preset position based on the dominant substrate set. When the optical field fitting operation ends, the dominant mode composition of the laser to be characterized is obtained. The dominant mode composition includes a dominant weight factor and a dominant mode corresponding to the dominant weight factor. The dominant weight factor and the dominant mode correspond one-to-one.

[0249] Specifically, after the excitation module 140 obtains the dominant basis set, in the light field fitting module 130, the weighting unit 131 sets the dominant weight recombination corresponding to the dominant basis set. The dominant weight recombination includes multiple dominant weight factors, and each dominant weight factor corresponds one-to-one with the dominant mode basis. The superposition unit 132 obtains the theoretical light field distribution based on the weighted superposition of the dominant basis set and the dominant weight set. The error unit 133 compares the difference between the theoretical light field distribution and the actual light field distribution to obtain the error coefficient. The comparison unit 134 compares the relative magnitude of the error coefficient with a preset error threshold to determine whether the error coefficient is less than or equal to the preset error threshold. When the error coefficient is less than or equal to the error threshold, the light field fitting is completed. Once the matching operation is completed, the mode unit 135 obtains the dominant mode composition. When the error coefficient is greater than the error threshold, the adjustment unit 136 adjusts the weight factor to obtain the adjusted dominant weight recombination, thereby reducing the difference between the error coefficient and the error threshold. After the adjustment unit 136 obtains the adjusted dominant weight recombination, the weight unit 131 resets the dominant weight recombination corresponding to the dominant basis group according to the adjusted dominant weight recombination. The superposition unit 132, the error unit 133, and the comparison unit 134 respectively re-execute the above-mentioned acquisition of theoretical light field distribution and comparison with actual light field distribution until the error coefficient is less than or equal to the error threshold. At this point, the light field fitting operation is completed, and the mode unit 135 obtains the dominant mode composition.

[0250] It should be noted that, based on the dominant substrate set and the actual light field distribution, the steps of the light field fitting module 130 in performing the light field fitting operation can refer to the aforementioned technical solution. The specific process of the light field fitting module 130 performing the light field fitting operation based on the complete substrate set and the actual light field distribution will not be repeated here again.

[0251] Specifically, the mode unit 135 uses the dominant weight factor obtained by the light field fitting operation as the dominant weight factor of the dominant mode composition, and the mode unit 135 uses the dominant mode basis corresponding to the dominant weight factor as the dominant mode in the dominant mode composition, thereby obtaining the dominant mode composition.

[0252] Continue to refer to Figure 16 After obtaining the dominant mode composition, the excitation module 140 is also adapted to use the dominant mode composition as the excitation mode composition, that is, the excitation module 140 uses the dominant mode in the dominant mode composition as the excitation mode, and the excitation module 140 uses the dominant weight factor corresponding to the dominant mode as the excitation weight factor corresponding to the excitation mode, thereby obtaining the excitation mode composition.

[0253] Refer to Table 3 and Figure 11 , Figure 12 Table 3 shows Figure 16 The illustrated representation of the complete power reorganization and dominance reorganization obtained by the device embodiment; Figure 11 It is a comparison of the theoretical and actual light field distributions at the near-field location when light field fitting operations are performed based on the complete basis set and the dominant basis set, respectively. Figure 12 This is a comparison of the theoretical and actual light field distributions at the far-field location, when light field fitting operations are performed based on the complete basis set and the dominant basis set, respectively.

[0254] When performing light field fitting based on a complete basis set, the complete basis set contains 27 complete mode basis sets. Therefore, upon completion of the light field fitting operation, the complete mode composition also contains 27 corresponding complete modes. The results of the obtained complete weighting factors are shown in Table 3. The first column represents the numbers of the 27 complete mode basis sets in the complete basis set, which are also the numbers of the complete modes in the complete mode composition. The second column represents the value of the complete weighting factor in the complete mode composition when the light field fitting operation based on the complete basis set is completed. The third column represents the value of the dominant weighting factor in the dominant mode composition when the light field fitting operation is completed again based on the dominant basis set.

[0255] Table 3

[0256]

[0257]

[0258] like Figure 11 and Figure 12 As shown, Figure 11The horizontal axis represents the polar radius in the aforementioned polar coordinate system, with the unit being micrometers (μm). The vertical axis represents the relative light intensity. The solid line represents the actual light field distribution, the dashed line represents the theoretical light field distribution when the light field fitting operation is completed based on the complete substrate set, and the dotted line represents the theoretical light field distribution when the light field fitting operation is completed again based on the dominant substrate set. Figure 12 The horizontal axis represents the zenith angle in the aforementioned spherical coordinate system, in degrees (deg). The solid line represents the actual light field distribution, the dashed line represents the theoretical light field distribution when the light field fitting operation is completed based on the complete basis set, and the dotted line represents the theoretical light field distribution when the light field fitting operation is completed again based on the dominant basis set.

[0259] according to Figure 12 The comparison results show that, based on the actual optical field distribution, the divergence angle of the laser to be characterized at the far-field position is approximately 21.24° (it should be noted that the divergence angle is the integral of the light intensity within this angle range accounting for 86% of the total energy of the cross section); based on the theoretical optical field distribution, the divergence angle of the laser to be characterized at the far-field position is approximately 20.16°. Therefore, it can be seen that the theoretical optical field distribution and the actual optical field distribution almost completely overlap at both the near-field and far-field positions, and the divergence angle obtained accordingly at the far-field position is also very close.

[0260] Furthermore, referring to Table 3, when performing the light field fitting operation based on the complete basis set, the complete basis set contains 27 complete mode basis sets; when the light field fitting operation is completed, the complete mode composition also contains 27 corresponding complete modes. Among them, the ratio of the complete weight factor corresponding to the complete mode numbered 18, complete mode numbered 22, complete mode numbered 23, and complete mode numbered 25 to the reference complete weight factor (maximum complete weight factor) is less than the dominant weight threshold. Therefore, these complete modes do not dominate in the complete mode composition and cannot be used as the dominant mode basis in the dominant basis set; the remaining complete modes are used as dominant mode basis sets to form the dominant basis set, and the light field fitting operation is performed again.

[0261] according to Figure 11 and Figure 12The comparison results show that, whether at the near-field or far-field position, the theoretical light field distribution obtained by performing light field fitting based on the complete basis set is essentially consistent with the theoretical light field distribution obtained by performing light field fitting again based on the dominant basis set. It should be noted that in this embodiment, the practice of obtaining the dominant mode composition through the complete mode composition, and then using the dominant mode composition as the excitation mode composition in the excitation module 140, is merely an example. In other embodiments of the present invention, the excitation mode module is suitable for using the complete mode composition as the excitation mode composition; that is, the excitation mode module directly uses the complete mode in the complete mode composition as the excitation mode, and uses the complete weight factor corresponding to the complete mode as the excitation weight factor corresponding to the excitation mode, thereby obtaining the excitation mode composition. In the above embodiments, the preset positions are far-field and near-field positions. That is, in the step of obtaining the actual light field distribution in the characterization method embodiment, the actual light field distribution at the near-field position and the actual light field distribution at the far-field position are obtained respectively. The light field fitting module 130 needs to perform light field fitting operations on the light field at the near-field position and the light field at the far-field position respectively to obtain the complete pattern composition. However, this approach is only an example. In other embodiments of the present invention, the preset position can also be one of the far-field position and the near-field position.

[0262] Refer to Table 4 and Figure 13 , Figure 14 This illustrates the results and comparisons of the optical field fitting operation during the characterization process of another embodiment of the laser performance characterization device of the present invention. Table 4 shows the complete weighted reassembly and dominant weighted reassembly obtained in the embodiment of the characterization method. Figure 13 It is a comparison of the theoretical and actual light field distributions at the far-field location when light field fitting operations are performed based on the complete basis set and the dominant basis set, respectively. Figure 14 It is the theoretical light field distribution at the near-field location when light field fitting operations are completed based on the complete basis set and the dominant basis set, respectively.

[0263] In this embodiment, the laser to be characterized is also a vertical-cavity surface-emitting laser, therefore the mode substrate in the obtained complete substrate set is the Laguerre-Gaussian light mode (e.g., Figure 5(As shown in the diagram). This embodiment has a smaller light-emitting window size, thus requiring fewer complete mode substrates. When performing light field fitting based on the complete substrate group, which contains 13 complete mode substrates, the complete mode composition also contains 13 corresponding complete modes upon completion of the light field fitting operation. The obtained complete weighting factor results are shown in Table 4. The first column represents the numbers of the 13 complete mode substrates in the complete substrate group, which are also the numbers of the complete modes in the complete mode composition; the second column represents the value of the complete weighting factor in the complete mode composition when the light field fitting operation based on the complete substrate group is completed; and the third column represents the value of the dominant weighting factor in the dominant mode composition when the light field fitting operation is completed again based on the dominant substrate group.

[0264] When performing light field fitting based on a complete basis set, the complete basis set contains 13 complete mode basis sets. Therefore, upon completion of the light field fitting operation, the complete mode composition also contains 13 corresponding complete modes. The results of the obtained complete weighting factors are shown in Table 4. The first column represents the numbers of the 13 complete mode basis sets in the complete basis set, which are also the numbers of the complete modes in the complete mode composition. The second column represents the value of the complete weighting factor in the complete mode composition when the light field fitting operation based on the complete basis set is completed. The third column represents the value of the dominant weighting factor in the dominant mode composition when the light field fitting operation is completed again based on the dominant basis set.

[0265] Reference Figure 13 The horizontal axis represents the zenith angle in the aforementioned spherical coordinate system, in degrees (deg), and the vertical axis represents the relative light intensity. The solid line 16a represents the actual light field distribution, and the dashed line 16b represents the theoretical light field distribution.

[0266] Reference Figure 13 The horizontal axis represents the zenith angle in the aforementioned spherical coordinate system, in degrees (deg), and the vertical axis represents the relative light intensity. The solid line 16a represents the actual light field distribution, and the dashed line 16b represents the theoretical light field distribution.

[0267] Table 4

[0268]

[0269] Based on the actual optical field distribution, the divergence angle of the laser to be characterized at the far field position is approximately 20.64°; based on the theoretical optical field distribution, the divergence angle at the far field position is approximately 21.60°. Furthermore, at the far field position, the theoretical and actual optical field distributions almost completely overlap.

[0270] Referring again to Table 4, when performing the light field fitting operation based on the complete basis set, the complete basis set contains 13 complete mode basis sets. When the light field fitting operation is completed, the complete mode composition also contains 13 corresponding complete modes. The maximum complete weight factor is used as the reference complete weight factor, and 1 / 10 is used as the dominant weight threshold. The ratio of the complete weight factor corresponding to the complete modes numbered 10-13 to the reference complete weight factor is less than the dominant weight threshold. Therefore, when performing the light field fitting operation based on the dominant basis set, the above-mentioned complete modes are omitted. That is, the remaining complete modes numbered 1-9 are used as dominant mode basis sets to form the dominant basis set, and the light field fitting operation is performed again.

[0271] Reference Figure 14 The horizontal axis represents the polar radius in the aforementioned polar coordinate system, with the unit being micrometers (μm). The vertical axis represents the relative light intensity. The solid line represents the actual light field distribution, the dashed line represents the theoretical light field distribution when the light field fitting operation is completed based on the complete substrate set, and the dotted line represents the theoretical light field distribution when the light field fitting operation is completed again based on the dominant substrate set.

[0272] Based on the theoretical light field distribution obtained from the second fitting, it can be determined that the divergence angle of the laser to be characterized at the far-field position is approximately 21.24°. Figure 13 When the optical field fitting operation is completed based on a complete basis set, the obtained theoretical optical field distribution is closer to the actual optical field distribution than the theoretical optical field distribution. Moreover, at the far field position, the theoretical optical field distribution and the actual optical field distribution almost completely overlap.

[0273] Therefore, it can be seen that the theoretical light field distribution obtained by performing light field fitting operation based on the complete substrate set is basically consistent with the theoretical light field distribution obtained by performing light field fitting operation again based on the dominant substrate set. That is, the composition of the dominant mode is consistent with the theoretical light field distribution reflected by the complete mode set.

[0274] In summary, the technical solution of this invention, based on the complete substrate set, obtains the complete mode composition of the laser to be characterized through optical field fitting, and obtains the excitation mode composition of the laser to be characterized according to the complete mode composition. The excitation mode composition includes: an excitation mode group and an excitation weighting group. The excitation mode group includes multiple excitation modes, and the excitation weighting group includes multiple excitation weighting factors, each corresponding one-to-one with an excitation mode. Therefore, this technical solution can obtain the number, order, and relative intensity information of the modes excited by the laser to be characterized in its operating state. Thus, different designs can be effectively evaluated from the perspective of modes, providing strong guidance for further design optimization of the optical performance of the device. Correspondingly, this invention also provides a light source design method. This design method adjusts the light source parameters based on the excitation modes obtained by the laser characterization method of this invention. It can more accurately characterize the optical performance of the laser from the perspective of micro-modes, which is beneficial for further optimization of the optical performance of the device and for further optimization of the performance of the designed light source.

[0275] While the present invention has been disclosed above, it is not limited thereto. Any person skilled in the art can make various modifications and alterations without departing from the spirit and scope of the invention; therefore, the scope of protection of the present invention should be determined by the scope defined in the claims.

Claims

1. A method for characterizing laser performance, characterized in that, include: Measure the actual optical field distribution of the optical field generated by the laser to be characterized at a preset position; Based on the laser to be characterized, a complete set of substrates is obtained, which includes multiple complete mode substrates. Based on the complete substrate set and the actual light field distribution, a light field fitting operation is performed on the light field formed by the laser to be characterized at a preset position. When the light field fitting operation ends, a complete mode composition of the laser to be characterized is obtained. The complete mode composition includes a complete mode set and a complete weighted set. The complete mode set includes multiple complete modes, and the complete weighted set includes multiple complete weight factors. The complete mode and the complete weight factor correspond one-to-one. Based on the complete mode composition of the laser to be characterized, the excitation mode composition of the laser to be characterized is obtained. The excitation mode composition includes: an excitation mode group and an excitation weight recombination. The excitation mode group includes multiple excitation modes, and the excitation weight recombination includes multiple excitation weight factors. The excitation weight factors correspond one-to-one with the excitation modes.

2. The characterization method as described in claim 1, characterized in that, The light field fitting operation includes: Set up a weighted reorganization corresponding to the base group. The base group includes multiple pattern bases. The weighted reorganization includes multiple weight factors. The weight factors correspond one-to-one with the pattern bases. The theoretical light field distribution is obtained by weighted superposition of the basis set and the weight set; By comparing the theoretical light field distribution with the actual light field distribution, the error coefficient is obtained; Determine whether the error coefficient is less than or equal to a preset error threshold; When the error coefficient is less than or equal to the error threshold, the light field fitting operation is completed and a pattern composition is obtained. The pattern composition includes a weight factor and a pattern corresponding to the weight factor. The weight factor and the pattern correspond one-to-one. When the error coefficient is greater than the error threshold, the weight factor is adjusted to obtain an adjusted weighted set to reduce the difference between the error coefficient and the error threshold. Based on the basis set and the adjusted weighted set, the steps of obtaining the theoretical light field distribution and the comparison steps are repeated until the error coefficient is less than or equal to the error threshold. The light field fitting operation is then completed, and the mode composition is obtained.

3. The characterization method as described in claim 1, characterized in that, The step of obtaining the excitation mode composition of the laser to be characterized based on the complete mode composition includes: using the complete mode composition as the excitation mode composition.

4. The characterization method as described in claim 1, characterized in that, The step of obtaining the excitation mode composition of the laser to be characterized based on the complete mode composition of the laser to be characterized includes: Based on the complete pattern composition, and combined with a preset dominant weight threshold, a dominant base group is obtained, which includes multiple dominant pattern bases. Based on the dominant basis set, the light field fitting operation is performed again on the light field formed by the laser to be characterized at a preset position. When the light field fitting operation ends, the dominant mode composition of the laser to be characterized is obtained. The dominant mode composition includes a dominant weight factor and a dominant mode corresponding to the dominant weight factor. The dominant weight factor and the dominant mode correspond one-to-one. The dominant mode is used as the excitation mode.

5. The characterization method as described in claim 4, characterized in that, The steps to obtain the dominant basement set include: Based on the complete pattern composition, a reference complete weight factor is obtained; Obtain the ratio of any complete weighting factor to the reference complete weighting factor; Compare the relative magnitude of the ratio with the dominant weight threshold; When the ratio is greater than or equal to the dominant weight threshold, the complete mode corresponding to the complete weight factor is a dominant mode basis in the dominant basis set.

6. The characterization method as described in claim 1, characterized in that, In the step of obtaining the actual light field distribution formed by the laser to be characterized at a preset position, the preset position includes at least one of a far-field position and a near-field position.

7. The characterization method as described in claim 1, characterized in that, The steps for obtaining a complete substrate set include: obtaining the complete substrate set based on the equivalent fiber model.

8. The characterization method as described in claim 7, characterized in that, The steps for obtaining the complete base set include: Based on the material of the laser to be characterized, the equivalent refractive index is obtained; Based on the structure of the laser to be characterized, the equivalent dimensions are obtained; Based on the equivalent refractive index and the equivalent size, an equivalent fiber model is established; Based on the equivalent fiber model, the waveguide modes transmitted in the equivalent fiber model are obtained. Based on the waveguide mode, a complete mode substrate is obtained to obtain a complete substrate set.

9. The characterization method as described in claim 8, characterized in that, In the step of obtaining a complete base set, all complete pattern bases are transverse patterns.

10. The characterization method as described in claim 2, characterized in that, The steps for obtaining the error coefficients include: obtaining the error coefficients based on the mean square error.

11. The characterization method as described in claim 10, characterized in that, The mean square error is the integral of the light intensity within a cross section perpendicular to the propagation direction at the preset position.

12. The characterization method as described in claim 2, characterized in that, The steps for adjusting the weight factors include: adjusting the weight factors based on a global optimization algorithm to obtain the adjusted weight factors.

13. The characterization method as described in claim 1, characterized in that, The laser to be characterized is a vertical cavity surface-emitting laser.

14. A light source design method, characterized in that, include: Provide lasers; The laser is characterized using the characterization method described in any one of claims 1 to 13 to obtain the excitation mode composition of the laser; Based on the aforementioned excitation modes, a light source is designed.

15. The light source design method as described in claim 14, characterized in that, The steps for designing a light source include: optimizing the parameters of the laser based on the excitation mode composition.

16. The light source design method as described in claim 14, characterized in that, The light source also includes: a collimating optical element; The steps for designing the light source also include: designing the collimating optical element based on the excitation mode composition.

17. The light source design method as described in claim 16, characterized in that, The collimating optical element includes a microlens.

18. A laser performance characterization device, characterized in that, include: The actual light field module is suitable for obtaining the actual light field distribution of the light field formed by the laser to be characterized at a preset position; A complete substrate module is suitable for obtaining a complete substrate set based on the laser to be characterized, the complete substrate set including multiple complete mode substrates. The light field fitting module is suitable for performing a light field fitting operation on the light field formed by the laser to be characterized at a preset position based on the complete basis set and the actual light field distribution. When the light field fitting operation is completed, a complete mode composition of the laser to be characterized is obtained. The complete mode composition includes a complete mode set and a complete weighted set. The complete mode set includes multiple complete modes, and the complete weighted set includes multiple complete weight factors. The complete modes and complete weight factors correspond one-to-one. An excitation mode module is adapted to obtain the excitation mode composition of the laser to be characterized based on the complete mode composition of the laser to be characterized. The excitation mode composition includes an excitation mode group and an excitation weight recombination. The excitation mode group includes multiple excitation modes, and the excitation weight recombination includes multiple excitation weight factors. The excitation weight factors correspond one-to-one with the excitation modes.

19. The characterization apparatus as claimed in claim 18, characterized in that, The light field fitting module includes: A weighting unit is suitable for setting a weighting reorganization corresponding to a base group. The base group includes multiple pattern bases, and the weighting reorganization includes multiple weight factors. The weight factors correspond one-to-one with the pattern bases. A superposition unit, which is adapted to obtain a theoretical light field distribution by weighted superposition of the basis set and the weight set; An error unit is provided, which is suitable for comparing the difference between the theoretical light field distribution and the actual light field distribution to obtain an error coefficient. A comparison unit, the comparison unit being adapted to compare the relative magnitude of the error coefficient with a preset error threshold; A pattern unit, wherein the error coefficient is less than or equal to the error threshold, the pattern unit is suitable for obtaining a pattern composition, the pattern composition including a weight factor and a pattern corresponding to the weight factor, the weight factor and the pattern being in one-to-one correspondence; When the error coefficient is greater than the error threshold, the adjustment unit is suitable for adjusting the size of the weighting factor to obtain an adjusted weighting set, so as to reduce the difference between the error coefficient and the error threshold. The weighting unit resets the weighting set corresponding to the basis set according to the adjusted weighting set. The superposition unit, the error unit, and the comparison unit respectively re-execute the above steps of obtaining the theoretical light field distribution, obtaining the error coefficient, and comparison until the error coefficient is less than or equal to the error threshold. The mode unit obtains the mode composition.

20. The characterization apparatus as claimed in claim 18, characterized in that, The excitation mode module is suitable for being composed of the complete mode as the excitation mode composition.

21. The characterization apparatus as claimed in claim 18, characterized in that, The activation mode module is suitable for obtaining a dominant base group based on the complete mode composition and combined with a preset dominant weight threshold, wherein the dominant base group includes multiple dominant mode bases. The optical field fitting module is also adapted to perform the optical field fitting operation again on the optical field formed by the laser to be characterized at a preset position based on the dominant basis set. When the optical field fitting operation ends, the dominant mode composition of the laser to be characterized is obtained. The dominant mode composition includes a dominant weight factor and a dominant mode corresponding to the dominant weight factor. The dominant weight factor and the dominant mode correspond one-to-one. The excitation mode module is also suitable to be composed of the dominant mode as the excitation mode component.

22. The characterization apparatus as claimed in claim 21, characterized in that, The excitation mode module includes: A reference unit, which is adapted to obtain a reference completeness weight factor based on the completeness pattern composition; A ratio unit, the ratio unit being adapted to obtain the ratio of any complete weighting factor to the reference complete weighting factor; A comparison ratio unit, the comparison ratio unit being adapted to compare the relative magnitude of the ratio with the dominant weight threshold; When the ratio is greater than or equal to the dominant weight threshold, the collection unit stores the complete pattern corresponding to the complete weight factor as a dominant pattern base in the dominant base group.

23. The characterization apparatus as claimed in claim 18, characterized in that, The preset position includes at least one of a far-field position and a near-field position.

24. The characterization apparatus as claimed in claim 18, characterized in that, The complete substrate module is suitable for obtaining the complete substrate set based on the equivalent fiber model.

25. The characterization apparatus as claimed in claim 24, characterized in that, The complete base module includes: The modeling unit is adapted to obtain the equivalent refractive index based on the material of the laser to be characterized, and to obtain the equivalent size based on the structure of the laser to be characterized; the modeling unit is also adapted to establish an equivalent fiber model based on the equivalent refractive index and the equivalent size. A substrate unit, which is adapted to obtain the waveguide modes transmitted in the equivalent fiber model based on the equivalent fiber model; and to obtain the complete mode substrate according to the waveguide modes transmitted in the equivalent fiber model, so as to obtain a complete substrate set.

26. The characterization apparatus as claimed in claim 25, characterized in that, All complete pattern bases are horizontal molds.

27. The characterization apparatus as claimed in claim 19, characterized in that, The error unit obtains the error coefficients based on the mean square error.

28. The characterization apparatus as claimed in claim 27, characterized in that, The mean square error is the integral of the light intensity within a cross section perpendicular to the propagation direction at the preset position.

29. The characterization apparatus as claimed in claim 19, characterized in that, The adjustment unit adjusts the weight factors based on a global optimization algorithm to obtain the adjusted weight factors.

30. The characterization apparatus as claimed in claim 18, characterized in that, The laser to be characterized is a vertical cavity surface-emitting laser.

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