Method for measuring reflectivity of coating film of semiconductor laser and semiconductor laser

Abstract

The invention provides a semiconductor laser coating reflectivity determination method and a semiconductor laser, and the method comprises the steps: generating a target relational expression according to the physical parameters of an equivalent mixing cavity formed by the semiconductor laser and an output coupling mirror, the target relational expression represents the relationship among the first reflectivity of the front cavity surface of the equivalent mixing cavity, the second reflectivity of the front cavity surface of the semiconductor laser and the third reflectivity of the output coupling mirror; different second reflectivity is selected from a second preset range, different third reflectivity is selected from a third preset range and substituted into the target relational expression, and a first preset range of the first reflectivity is determined; under the condition that the first preset range covers the target range, verifying the mode of the equivalent mixing cavity; and under the condition that the equivalent mixing cavity mode is dominated by the inner cavity mode of the semiconductor laser, testing the output performance of the semiconductor laser by using a reflectivity measuring device, and determining the target coating reflectivity of the semiconductor laser based on the output performance.

Description

Technical Field

[0001] This disclosure relates to the fields of optics and semiconductor technology, specifically to a method for measuring the reflectivity of a semiconductor laser coating and a semiconductor laser. Background Technology

[0002] Semiconductor lasers possess numerous advantages, including high power, high reliability, long lifespan, small size, and low cost, and are widely used in pumping, medical, and communication fields. After growth and processing, semiconductor lasers require coating on their front and rear cavity surfaces to improve output performance, protect these surfaces, and extend their lifespan.

[0003] Depositing a high-reflectivity coating on the back cavity and an anti-reflection coating on the front cavity surface allows almost all light to exit from the front cavity surface, increasing power and efficiency while reducing the threshold current. Excessive reflectivity of the front cavity surface coating can suppress device performance, reduce laser output power, exacerbate thermal effects, and easily lead to catastrophic optical mirror damage (COMD) at the front cavity surface, resulting in laser device failure. Conversely, excessively low front cavity surface reflectivity increases the laser's threshold current, leading to reduced mode stability and linewidth broadening. Therefore, confirming the reflectivity of the front cavity coating is a crucial step before the laser coating process. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this disclosure provides a method for measuring the reflectivity of a semiconductor laser coating and a semiconductor laser, enabling the determination of a superior reflectivity of the front cavity surface of a semiconductor laser in a low-cost and convenient manner.

[0005] The first aspect of this disclosure provides a method for measuring the reflectivity of a semiconductor laser coating, comprising: generating a target relational expression based on the physical parameters of an equivalent hybrid cavity formed by the semiconductor laser and an output coupling mirror, wherein the target relational expression characterizes the relationship between a first reflectivity of the front cavity surface of the equivalent hybrid cavity, a second reflectivity of the front cavity surface of the semiconductor laser, and a third reflectivity of the output coupling mirror; selecting different second reflectivities from a second preset range and different third reflectivities from a third preset range and substituting them into the target relational expression to determine a first preset range of the first reflectivity; verifying the mode of the equivalent hybrid cavity when the equivalent hybrid cavity mode is dominated by the internal cavity mode of the semiconductor laser; and testing the output performance of the semiconductor laser using a reflectivity measuring device when the equivalent hybrid cavity mode is dominated by the internal cavity mode of the semiconductor laser, and determining the target coating reflectivity of the semiconductor laser based on the output performance.

[0006] According to embodiments of this disclosure, a target relational expression is generated based on the physical parameters of the equivalent hybrid cavity formed by the semiconductor laser and the output coupling mirror. This includes: determining a first relational expression for the complex reflection coefficient of the front cavity surface of the equivalent hybrid cavity based on the wavelength of the semiconductor laser, the internal effective refractive index and the refractive index of the external cavity medium of the semiconductor laser, the length of the external cavity medium of the semiconductor laser, the mirror refractive index of the output coupling mirror, and the coupling efficiency of the output coupling mirror to the semiconductor laser; and performing a conjugate operation based on the first relational expression to obtain the target relational expression.

[0007] According to embodiments of this disclosure, the target relation expression includes:

[0008]

[0009] in, The first reflectivity, The second reflectivity, The third reflectivity, Let be the reflection coefficient at the front cavity surface of the semiconductor laser. This is the reflection coefficient at the output coupling mirror. The round-trip phase difference of the laser mode in the external cavity. The wavelength of a semiconductor laser. The internal effective refractive index of a semiconductor laser. The refractive index of the external cavity medium of the semiconductor laser. The length of the external cavity medium of the semiconductor laser. To output the refractive index of the coupling mirror, The coupling efficiency of the output coupling mirror to the semiconductor laser.

[0010] According to embodiments of this disclosure, when the first preset range covers the target range, verifying the mode of the equivalent mixing cavity includes: establishing an equivalent mixing cavity mode competition model; calculating and comparing mode competition representative parameters based on the established equivalent mixing cavity mode competition model to verify the mode of the equivalent mixing cavity.

[0011] According to embodiments of this disclosure, the equivalent hybrid cavity mode is verified by calculating and comparing representative parameters of mode competition based on an established equivalent hybrid cavity mode competition model. This includes: determining the threshold gain corresponding to the inner cavity of the semiconductor laser based on the device internal loss, the cavity length of the semiconductor laser, the reflectivity of the rear cavity surface of the semiconductor laser, and the reflectivity of the front cavity surface of the semiconductor laser; determining the threshold gain corresponding to the outer cavity of the semiconductor laser based on the device internal loss, the cavity length of the semiconductor laser, the length of the outer cavity medium of the semiconductor laser, the reflectivity of the rear cavity surface of the semiconductor laser, and a first reflectivity; and determining the threshold gain corresponding to the outer cavity of the semiconductor laser based on the mode confinement factor of the outer cavity of the semiconductor laser, the semiconductor laser... The net mode gain of the semiconductor laser's external cavity is determined by the peak gain of the material at the corresponding wavelength and the threshold gain of the external cavity. The net mode gain of the semiconductor laser's internal cavity is determined by the mode confinement factor within the cavity, the peak gain of the semiconductor laser material at the corresponding wavelength, and the threshold gain of the internal cavity. The net mode gain difference between the internal and external cavities is determined by the net mode gain of the internal and external cavities. When the net mode gain difference is greater than zero, the equivalent hybrid cavity mode is determined to be the dominant mode of the semiconductor laser's internal cavity.

[0012] According to embodiments of this disclosure, the reflectivity measuring device includes: a light source module, a collimation module, and a testing module; testing the output performance of a semiconductor laser using the reflectivity measuring device includes: outputting the semiconductor laser to be tested through the light source module; collimating the semiconductor laser through the collimation module to obtain the collimated laser; testing the collimated laser through the testing module to obtain the output power and spectral characteristics of the semiconductor laser; and adjusting the third reflectivity of the output coupling mirror to obtain multiple sets of output power and spectral characteristics.

[0013] According to embodiments of this disclosure, the light source module includes at least one semiconductor laser or semiconductor laser bar, and at least one output coupling mirror; each laser or bar has one or more light-emitting regions; the output coupling mirror includes a plane mirror, curved mirror, or composite mirror with adjustable reflectivity, or a set of output coupling mirrors with constant reflectivity.

[0014] According to embodiments of this disclosure, the collimation module includes a fast-axis collimating lens and a slow-axis collimating lens, and the operating wavelengths of the fast-axis collimating lens and the slow-axis collimating lens include the near-infrared band or the mid-infrared band.

[0015] According to embodiments of this disclosure, the test module includes a beam splitter, a power meter, and a spectrometer. The beam splitter splits the collimated laser into two beams. The power meter measures the output power of the semiconductor laser based on one beam, and the spectrometer measures the spectral characteristics of the semiconductor laser based on the other beam. The beam splitting ratio of the beam splitter is 1:1 to 1:9.

[0016] The second aspect of this disclosure provides a semiconductor laser, wherein the reflectivity of a reflective film coated on the semiconductor laser is determined based on the above-described measurement method.

[0017] The method for measuring the reflectivity of semiconductor laser coatings and the semiconductor laser disclosed herein have at least the following technical advantages.

[0018] Output couplers (OCs) with different reflectivities are placed on the outer side of the laser front cavity surface. By changing the reflectivity of the output couplers instead of the front cavity coating process, the front cavity surface of the semiconductor laser and the output couplers are equivalent to the front cavity surface of an equivalent hybrid cavity. By changing the reflectivity of the output couplers, the reflectivity of the equivalent hybrid cavity front cavity surface is changed. Then, a better front cavity surface reflectivity is obtained by comparison and measurement, thereby saving the process cost and time cost of repeated coating. The relatively better value is obtained through experimental measurement, reducing the error between pure theoretical calculation and actual test. Attached Figure Description

[0019] The foregoing contents, as well as other objects, features, and advantages of this disclosure, will become clearer from the following description of embodiments with reference to the accompanying drawings, in which:

[0020] Figure 1 The diagram illustrates the variation of higher electro-optic conversion efficiency of semiconductor lasers with different cavity lengths with front cavity reflectivity, without considering thermal effects.

[0021] Figure 2 A flowchart illustrating a method for measuring the reflectivity of a semiconductor laser coating according to an embodiment of the present disclosure is shown.

[0022] Figure 3 The schematic diagram illustrates a semiconductor laser and its output coupling mirror as an equivalent hybrid cavity according to an embodiment of the present disclosure.

[0023] Figure 4 The schematic illustration shows the equivalent hybrid cavity front surface reflectivity R according to an embodiment of the present disclosure. eff The reflectivity R2 of the front cavity surface of the semiconductor laser and the reflectivity R of the output coupling mirror vary. OC The relationship diagram of the changes.

[0024] Figure 5 This schematically illustrates the difference between the intracavity mode gain and the equivalent hybrid cavity mode gain according to embodiments of the present disclosure as a function of the front cavity surface reflectivity R2 of the semiconductor laser and the output coupling mirror reflectivity R. OC Distribution map of the changes.

[0025] Figure 6 A schematic diagram of a semiconductor laser front cavity surface better reflectivity measuring device according to an embodiment of the present disclosure is shown.

[0026] Reference numerals: 1-Semiconductor external cavity laser; 2-Equivalent hybrid cavity; 3-Semiconductor laser; 4-Output coupling mirror; 5-Rear cavity surface of semiconductor laser; 6-Front cavity surface of semiconductor laser; 7-Reflecting surface of output coupling mirror; 8-Inner cavity of semiconductor laser; 9-External cavity medium; 10-Rear cavity surface of equivalent hybrid cavity; 11-Front cavity surface of equivalent hybrid cavity; 12-Cavity length of equivalent hybrid cavity; 13-Light source module; 14-Collimation module; 15-Test module; 16-Semiconductor laser; 17-Output coupling mirror; 18-Fast axis collimating mirror; 19-Slow axis collimating mirror; 20-Beam splitter; 21-Power meter; 22-Spectrometer. Detailed Implementation

[0027] The embodiments of the present disclosure will now be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the disclosure. In the following detailed description, numerous specific details are set forth to provide a thorough understanding of the embodiments of the present disclosure for ease of explanation. However, it will be apparent that one or more embodiments may be practiced without these specific details. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concepts of the present disclosure.

[0028] Figure 1 The diagram illustrates the variation of the highest electro-optical conversion efficiency of semiconductor lasers with different cavity lengths with front cavity reflectivity, without considering thermal effects.

[0029] Currently, theoretical calculations have confirmed that, without considering thermal effects, for a laser with a fixed cavity length and back cavity reflectivity, there exists a superior reflectivity at the front cavity surface that enables the device to achieve higher electro-optical conversion efficiency, thereby obtaining better output performance, such as... Figure 1 As shown.

[0030] Currently, there are two main methods for determining the optimal front cavity reflectivity: experimental measurement and simulation calculation. Simulation calculation is relatively simple, but the results will have a large error compared with the actual experimental test. The process of repeated coating for experimental comparison is more complicated, and the experimental time and process cost are also higher.

[0031] In view of this, embodiments of the present disclosure provide a method for measuring the reflectivity of a semiconductor laser coating and a semiconductor laser. Detailed descriptions are provided below with reference to specific embodiments.

[0032] Figure 2 A flowchart illustrating a method for measuring the reflectivity of a semiconductor laser coating according to an embodiment of the present disclosure is shown.

[0033] like Figure 2As shown, the method for measuring the reflectivity of the semiconductor laser coating in this embodiment may include, for example, operations S210 to S240.

[0034] In operation S210, a target relational expression is generated based on the physical parameters of the equivalent hybrid cavity formed by the semiconductor laser and the output coupling mirror. The target relational expression characterizes the relationship between the first reflectivity of the front cavity surface of the equivalent hybrid cavity, the second reflectivity of the front cavity surface of the semiconductor laser, and the third reflectivity of the output coupling mirror.

[0035] In operation S220, different second reflectivities are selected from the second preset range, and different third reflectivities are selected from the third preset range. These are then substituted into the target relational expression to determine the first preset range of the first reflectivity.

[0036] In operation S230, the mode of the equivalent mixing chamber is verified when the first preset range covers the target range.

[0037] In operation S240, with the equivalent hybrid cavity mode dominated by the internal cavity mode of the semiconductor laser, the output performance of the semiconductor laser is tested using a reflectivity measuring device, and the target coating reflectivity of the semiconductor laser is determined based on the output performance.

[0038] Figure 3 The schematic diagram illustrates a semiconductor laser and its output coupling mirror as an equivalent hybrid cavity according to an embodiment of the present disclosure.

[0039] like Figure 3 As shown, the semiconductor external cavity laser 1 can be composed of an FP-cavity semiconductor laser 3, a planar output coupling mirror 4, and an external cavity medium 9. The semiconductor laser 3 may include: a semiconductor laser rear cavity surface 5, a semiconductor laser front cavity surface 6, and a semiconductor laser inner cavity 8. The output coupling mirror 4 may include an output coupling mirror reflector 7; the equivalent hybrid cavity 2 may include: an equivalent hybrid cavity rear cavity surface 10, an equivalent hybrid cavity front cavity surface 11, and an equivalent hybrid cavity medium 12.

[0040] For the external cavity, the effective refractive index inside the semiconductor laser is n1, the reflectivity of the front cavity surface is R2, the reflectivity of the rear cavity surface is R1, and the cavity length is L. a The output coupling mirror reflectivity is R OC The length of the external cavity medium of the semiconductor laser is L. b The refractive index of the external cavity medium is n2, and the refractive index of the mirror is n3. The three-layer medium of the semiconductor laser, external cavity medium, and output coupling mirror can be regarded as the equivalent front cavity surface.

[0041] According to embodiments of this disclosure, output coupling mirrors with different reflectivities are placed on the outer side of the front cavity surface of a semiconductor laser. The front cavity surface of the semiconductor laser and the output coupling mirror are equivalent to the front cavity surface of an equivalent hybrid cavity by changing the reflectivity of the output coupling mirror instead of the front cavity coating process. The reflectivity of the equivalent hybrid cavity front cavity surface is changed by changing the reflectivity of the output coupling mirror, and then a better front cavity surface reflectivity is obtained by comparison and measurement.

[0042] In some embodiments, generating a target relational expression based on the physical parameters of the equivalent hybrid cavity formed by the semiconductor laser and the output coupling mirror may include: determining a first relational expression for the complex reflection coefficient of the front cavity surface of the equivalent hybrid cavity based on the wavelength of the semiconductor laser, the internal effective refractive index and the refractive index of the external cavity medium of the semiconductor laser, the length of the external cavity medium of the semiconductor laser, the mirror refractive index of the output coupling mirror, and the coupling efficiency of the output coupling mirror to the semiconductor laser. The target relational expression is obtained by performing a conjugate operation based on the first relational expression.

[0043] For example, the complex reflection coefficient of the equivalent hybrid cavity front surface according to the three-layer transfer matrix algorithm The first relational expression can be:

[0044]

[0045] in Let be the reflection coefficient at the front cavity surface of the semiconductor laser. This is the reflection coefficient at the output coupling mirror. Let be the round-trip phase difference of the laser mode in the external cavity. Considering the coupling loss caused by the output coupling mirror, and assuming the coupling efficiency of the external cavity optical feedback coupling into the semiconductor laser is η, then the complex reflection coefficient of the equivalent hybrid cavity front surface is:

[0046]

[0047] In some embodiments, the effective reflectivity R of the front cavity surface of the equivalent hybrid cavity eff for:

[0048]

[0049] in, The first reflectivity, The second reflectivity, The third reflectivity, Let be the reflection coefficient at the front cavity surface of the semiconductor laser. This is the reflection coefficient at the output coupling mirror. The round-trip phase difference of the laser mode in the external cavity. λ is the wavelength of the semiconductor laser.

[0050] Based on the above process, the equivalent hybrid cavity was modeled, and the reflectivity expression of the front cavity surface of the equivalent hybrid cavity was obtained.

[0051] Furthermore, after determining the target relational expression, a semiconductor laser of a certain wavelength is selected, and the coupling efficiency of the external cavity optical feedback coupled into the semiconductor laser is determined. The distance L between the front cavity surface and the output coupling mirror of the semiconductor laser b =2cm, refractive index of the outer cavity medium n2=1, and based on prior knowledge, a better reflectivity R is initially considered. eff The target range is between 0.1% and 5%.

[0052] A set of semiconductor lasers were selected with front cavity reflectivities R² of 0.1%, 0.46%, 0.85%, 1.23%, 1.62%, and 2%, respectively; the output coupler reflectivity R... OC 100 points were uniformly selected within the range of 0.1%-10% for scanning calculation to obtain the effective reflectivity R of the front cavity surface of the equivalent hybrid cavity. eff The curve showing the change.

[0053] Figure 4 The schematic illustration shows the equivalent hybrid cavity front surface reflectivity R according to an embodiment of the present disclosure. eff The reflectivity R2 of the front cavity surface of the semiconductor laser and the reflectivity R of the output coupling mirror vary. OC The relationship diagram of the changes.

[0054] like Figure 4 As shown. In this embodiment, the initial front cavity reflectivity of the semiconductor laser is selected as R2 = 0.46%, and the output coupling mirror reflectivity is R... OC With a range of 0.5%-9.5%, the effective reflectivity R of the front cavity surface of the equivalent hybrid cavity can be observed. eff The range is 0.02%-5.3%, covering the range of 0.1%-5% where the front cavity surface of semiconductor lasers has better reflectivity.

[0055] In some embodiments, when the first preset range covers the target range, verifying the modes of the equivalent mixing cavity may include: establishing an equivalent mixing cavity mode competition model. Based on the established equivalent mixing cavity mode competition model, representative parameters of mode competition are calculated and compared to verify the modes of the equivalent mixing cavity. Representative parameters of mode competition may include parameters such as mode gain, mode loss, and quality factor.

[0056] Furthermore, based on the establishment of an equivalent hybrid cavity mode competition model, representative parameters of mode competition are calculated and compared to verify the modes of the equivalent hybrid cavity. This includes: determining the threshold gain corresponding to the inner cavity of the semiconductor laser based on the device internal loss, the cavity length of the semiconductor laser, the reflectivity of the rear cavity surface of the semiconductor laser, and the reflectivity of the front cavity surface of the semiconductor laser; determining the threshold gain corresponding to the outer cavity of the semiconductor laser based on the device internal loss, the cavity length of the semiconductor laser, the length of the outer cavity medium of the semiconductor laser, the reflectivity of the rear cavity surface of the semiconductor laser, and the first reflectivity; and determining the threshold gain corresponding to the outer cavity of the semiconductor laser based on the mode confinement factor of the outer cavity of the semiconductor laser and the semiconductor laser material at the corresponding wavelength. The net gain of the external cavity mode of the semiconductor laser is determined by the peak gain and the threshold gain corresponding to the external cavity of the semiconductor laser. The net gain of the internal cavity mode of the semiconductor laser is determined by the mode confinement factor inside the semiconductor laser cavity, the peak gain of the semiconductor laser material at the corresponding wavelength, and the threshold gain corresponding to the internal cavity of the semiconductor laser. The net gain difference between the internal and external cavity modes of the semiconductor laser is determined by the net gain of the internal and external cavity modes of the semiconductor laser. When the net gain difference between the internal and external cavities of the semiconductor laser is greater than zero, the equivalent hybrid cavity mode is determined to be the dominant mode of the internal cavity of the semiconductor laser.

[0057] For example, using mode gain as a representative parameter of mode competition between the inner and outer cavities, and placing the output coupling mirror as close as possible to the front cavity surface of the semiconductor laser, the outer cavity gain and the inner cavity gain can be considered to be the same.

[0058] For the internal cavity of a semiconductor laser, there exists a threshold gain. :

[0059] .

[0060] For the external cavity of a semiconductor laser, there exists a threshold gain. :

[0061] .

[0062] So, the net gain of the external cavity mode of the semiconductor laser for:

[0063] .

[0064] So, the net gain of the cavity mode of the semiconductor laser for:

[0065] .

[0066] The net mode gain difference between the inner and outer cavities of a semiconductor laser can be calculated. for:

[0067] .

[0068] in, The mode confinement factor within the cavity of a semiconductor laser. External cavity mode constraint factor, This represents the peak gain of the semiconductor laser material at the corresponding wavelength. R1 is the internal loss of the device, R2 is the reflectivity of the back cavity surface of the semiconductor laser, and R2 is the reflectivity of the front cavity surface of the semiconductor laser.

[0069] If the net gain difference This indicates that in the competition between the external cavity mode and the internal cavity mode, the internal cavity mode is dominant. Therefore, the internal cavity mode is the dominant mode in the equivalent mixing cavity, and the front surface reflectivity R of the equivalent mixing cavity is high. eff It can be considered as an equivalent of the front cavity surface of the internal cavity of a semiconductor laser.

[0070] Figure 5 This schematically illustrates the difference between the intracavity mode gain and the equivalent hybrid cavity mode gain according to embodiments of the present disclosure as a function of the front cavity surface reflectivity R2 of the semiconductor laser and the output coupling mirror reflectivity R. OC Distribution map of the changes.

[0071] like Figure 5 As shown, the cavity length L of the semiconductor laser is selected. a =4 mm, peak gain of semiconductor laser material External cavity mode limiting factor Mode confinement factor within the cavity of a semiconductor laser The reflectivity of the back cavity surface of the semiconductor laser is R1 = 0.99. The equivalent hybrid cavity front cavity surface reflectivity R calculated in step S1 is used. eff The calculations show that R2 = 0.1%-2% at the front cavity surface of the semiconductor laser and R... OC The net gain difference between the inner cavity and the equivalent mixing cavity within the range of 0.1% to 10% Distribution. It exists across all ranges obtained based on these parameters. This indicates that, within the initial front cavity reflectivity R2 = 0.46% of the semiconductor laser and the output coupling mirror reflectivity range of 0.5%-9.5% determined in this embodiment, the equivalent hybrid cavity mode is dominated by the semiconductor laser's internal cavity mode. The reflectivity R2 of the equivalent hybrid cavity front surface is... eff It can be equivalent to the front cavity surface of a semiconductor laser.

[0072] In some embodiments, the reflectivity measuring device may include a light source module, a collimation module, and a testing module. Testing the output performance of a semiconductor laser using the reflectivity measuring device may include: outputting the semiconductor laser to be tested through the light source module; collimating the semiconductor laser through the collimation module to obtain the collimated laser; and testing the collimated laser through the testing module to obtain the output power and spectral characteristics of the semiconductor laser. Adjusting the third reflectivity of the output coupling mirror yields multiple sets of output power and spectral characteristics.

[0073] In some embodiments, the light source module includes at least one semiconductor laser or semiconductor laser bar, and at least one output coupling mirror; each laser or bar has one or more light-emitting areas; the output coupling mirror includes a plane mirror, curved mirror, or composite mirror with adjustable reflectivity, or a set of output coupling mirrors with constant reflectivity.

[0074] It should be understood that when testing with a plane mirror, curved mirror, or composite mirror with adjustable reflectivity, the reflectivity is adjusted directly; when testing with a set of output couplers with constant reflectivity, the test is repeated by changing the output couplers with different constant reflectivity.

[0075] In some embodiments, the collimation module includes a series of optical collimation elements, such as a fast-axis collimator and a slow-axis collimator, the operating bands of which include those involved in semiconductor lasers, such as infrared and mid-infrared.

[0076] In some embodiments, the test module includes a beam splitter, a power meter, and a spectrometer. The beam splitter divides the collimated laser into two beams. The power meter measures the output power of the semiconductor laser based on one beam, and the spectrometer measures the spectral characteristics of the semiconductor laser based on the other beam. The beam splitter covers wavelengths relevant to semiconductor lasers, such as near-infrared and mid-infrared. The beam splitting ratio of the beam splitter is from 1:1 to 1:9.

[0077] Figure 6 A schematic diagram of a semiconductor laser front cavity surface better reflectivity measuring device according to an embodiment of the present disclosure is shown.

[0078] For example, such as Figure 6 As shown, the reflectivity measuring device may include: a light source module 13, a collimation module 14, and a test module 15. The light source module 13 consists of a semiconductor laser 16 and an output coupling mirror 17, the collimation module 14 consists of a fast-axis collimating mirror 18 and a slow-axis collimating mirror 19, and the test module consists of a 50% beam splitter 20, a power meter 21, and a spectrometer 22.

[0079] A semiconductor laser 16 and an output coupling mirror 17 form an external cavity. The laser beam, output from the external cavity, is collimated by a fast-axis collimating mirror 18 and a slow-axis collimating mirror 18, and then split into two beams by a beam splitter 20. One beam enters a power meter 21 to measure the laser power, and the other beam enters a spectrometer 22 to measure its spectral performance. After completing one laser power and spectral characteristic test, the reflectivity of the output coupling mirror 17 is changed, and the test continues. After completing the test, the reflectivity R of the output coupling mirror 17 with the best output characteristics is obtained. OC Its corresponding equivalent hybrid cavity front cavity surface reflectivity This results in the final, superior coating reflectivity.

[0080] Based on the above-described method for measuring the reflectivity of semiconductor laser coatings, embodiments of this disclosure also provide a semiconductor laser, wherein the reflectivity of the reflective film coated on the semiconductor laser is measured using the above-described method, and specific details will not be repeated here.

[0081] The embodiments of this disclosure have been described above. However, these embodiments are for illustrative purposes only and are not intended to limit the scope of this disclosure. Although various embodiments have been described above, this does not mean that the measures in the various embodiments cannot be used advantageously in combination. The scope of this disclosure is defined by the appended claims and their equivalents. Various substitutions and modifications can be made by those skilled in the art without departing from the scope of this disclosure, and all such substitutions and modifications should fall within the scope of this disclosure.

Claims

1. A method for measuring the reflectivity of a semiconductor laser coating, characterized in that, include: Based on the physical parameters of the equivalent hybrid cavity formed by the semiconductor laser and the output coupling mirror, a target relational expression is generated. The target relational expression characterizes the relationship between the first reflectivity of the front cavity surface of the equivalent hybrid cavity, the second reflectivity of the front cavity surface of the semiconductor laser, and the third reflectivity of the output coupling mirror. Different second reflectances are selected from the second preset range, and different third reflectances are selected from the third preset range. These are then substituted into the target relational expression to determine the first preset range of the first reflectance. Verify the mode of the equivalent mixing cavity when the first preset range covers the target range; When the equivalent hybrid cavity mode is dominated by the internal cavity mode of the semiconductor laser, the output performance of the semiconductor laser is tested using a reflectivity measuring device, and the target coating reflectivity of the semiconductor laser is determined based on the output performance.

2. The determination method according to claim 1, characterized in that, The step of generating the target relational expression based on the physical parameters of the equivalent hybrid cavity formed by the semiconductor laser and the output coupling mirror includes: Based on the wavelength of the semiconductor laser, the internal effective refractive index and the refractive index of the external cavity medium of the semiconductor laser, the length of the external cavity medium of the semiconductor laser, the mirror refractive index of the output coupling mirror, and the coupling efficiency of the output coupling mirror to the semiconductor laser, a first relational expression for the complex reflection coefficient of the front cavity surface of the equivalent hybrid cavity is determined. The target relational expression is obtained by performing conjugate operations based on the first relational expression.

3. The determination method according to claim 2, characterized in that, The target relation expression includes: in, The first reflectivity, The second reflectivity, The third reflectivity, Let be the reflection coefficient at the front cavity surface of the semiconductor laser. This is the reflection coefficient at the output coupling mirror. The round-trip phase difference of the laser mode in the external cavity. The wavelength of the semiconductor laser is [wavelength]. The internal effective refractive index of the semiconductor laser is given. The refractive index of the external cavity medium of the semiconductor laser is given. The length of the external cavity medium of the semiconductor laser is given. The refractive index of the output coupling mirror is given. The coupling efficiency of the output coupling mirror to the semiconductor laser.

4. The determination method according to claim 1, characterized in that, When the first preset range covers the target range, verify the mode of the equivalent mixing cavity, including: Establish an equivalent hybrid cavity mode competition model; Based on the established equivalent hybrid cavity mode competition model, the representative parameters of the mode competition are calculated and compared to verify the mode of the equivalent hybrid cavity.

5. The determination method according to claim 4, characterized in that, The step of calculating and comparing representative parameters of the mode competition based on the established equivalent hybrid cavity mode competition model to verify the mode of the equivalent hybrid cavity includes: The threshold gain corresponding to the internal cavity of the semiconductor laser is determined based on the internal loss of the device, the cavity length of the semiconductor laser, the reflectivity of the rear cavity surface of the semiconductor laser, and the reflectivity of the front cavity surface of the semiconductor laser. The threshold gain corresponding to the external cavity of the semiconductor laser is determined based on the internal loss of the device, the cavity length of the semiconductor laser, the length of the external cavity medium of the semiconductor laser, the reflectivity of the rear cavity surface of the semiconductor laser, and the first reflectivity. The net mode gain of the external cavity of the semiconductor laser is determined based on the mode confinement factor of the external cavity of the semiconductor laser, the peak gain of the semiconductor laser material at the corresponding wavelength, and the threshold gain corresponding to the external cavity of the semiconductor laser. The net gain of the semiconductor laser cavity mode is determined based on the mode confinement factor within the semiconductor laser cavity, the peak gain of the semiconductor laser material at the corresponding wavelength, and the threshold gain corresponding to the semiconductor laser cavity. The difference between the mode net gain of the internal cavity and the external cavity of the semiconductor laser is determined based on the net gain of the internal cavity mode and the net gain of the external cavity mode of the semiconductor laser. If the net gain difference between the modes is greater than zero, the equivalent hybrid cavity mode is determined to be dominated by the semiconductor laser cavity mode.

6. The determination method according to claim 1, characterized in that, The reflectance measuring device includes: a light source module, a collimation module, and a testing module; The method of testing the output performance of the semiconductor laser using a reflectivity measuring device includes: The required semiconductor laser is output through the light source module; The semiconductor laser is collimated using the collimation module to obtain a collimated laser. The test module is used to test the aligned laser to obtain the output power and spectral characteristics of the semiconductor laser. By adjusting the third reflectivity of the output coupling mirror, multiple sets of output power and spectral characteristics are obtained.

7. The determination method according to claim 6, characterized in that, The light source module includes at least one semiconductor laser or semiconductor laser bar, and at least one output coupling mirror; each laser or bar has one or more light-emitting areas; the output coupling mirror includes a plane mirror, curved mirror, or composite mirror with adjustable reflectivity, or a set of output coupling mirrors with constant reflectivity.

8. The determination method according to claim 6, characterized in that, The collimation module includes a fast-axis collimating lens and a slow-axis collimating lens, and the operating wavelengths of the fast-axis collimating lens and the slow-axis collimating lens include the near-infrared band or the mid-infrared band.

9. The determination method according to claim 6, characterized in that, The testing module includes a beam splitter, a power meter, and a spectrometer. The beam splitter splits the collimated laser into two beams. The power meter measures the output power of the semiconductor laser based on one beam, and the spectrometer measures the spectral characteristics of the semiconductor laser based on the other beam. The beam splitter has a splitting ratio of 1:1 to 1:

9.

10. A semiconductor laser, characterized in that, The reflectivity of the reflective film coated on the semiconductor laser is determined according to the measurement method described in any one of claims 1 to 9.

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