Semiconductor laser external cavity wave locking grating screening device and screening method

Abstract

The invention provides a semiconductor laser external cavity wave locking grating screening device and screening method, and relates to the technical field of semiconductor lasers. The screening device comprises a chip, and a fast axis collimating mirror, a slow axis collimating mirror and a laser beam splitter are sequentially arranged on the light emitting side of the chip in the light emitting direction. A first test bench is arranged between the fast axis collimating mirror and the slow axis collimating mirror, and a second test bench is arranged between the slow axis collimating mirror and the laser beam splitter. A power meter is arranged on the transmission light emergent side of the laser beam splitter, and an attenuation piece and a spectrograph are sequentially arranged on the reflected light emergent side of the laser beam splitter in the light emergent direction. According to the screening method, the volume grating is screened in advance in a mode of testing the power loss rate and the wave locking current range, data support is provided for later selection and use of the volume grating, the steps of repeated repairing and testing are omitted, the cost is reduced, and the consistency and the production efficiency of the whole product are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor lasers, in particular to a semiconductor laser external cavity wave-locked body grating screening device and screening method. Background Art

[0002] Laser has the advantages of good monochromaticity, good directionality, good coherence, and high brightness. Laser has been widely used in various fields of the national economy, such as laser cutting, laser welding, beauty, medical equipment, communications, indication, night vision, weapons, etc.

[0003] Semiconductor laser devices (LDs) also have inherent flaws, including poor spot quality. They typically require a series of complex optical systems to achieve a usable spot. The light-emitting surface of a semiconductor laser chip is divided into two directions: the fast axis and the slow axis. The divergence angle in the slow axis is relatively small, but the light-emitting area is wider, ranging from several to hundreds of times the size of the fast axis. Before coupling the light emitted by the semiconductor laser device into an optical fiber, the light in the fast and slow axis directions needs to be compressed and shaped.

[0004] Semiconductor lasers have a large wavelength linewidth, typically 2-5nm at half-width. At certain wavelengths or in specialized applications, extremely stringent wavelength requirements exist, requiring an extremely narrow linewidth to maintain proper operation. In these cases, external cavity locking is necessary. After external cavity locking, the linewidth is typically reduced to less than 0.5nm.

[0005] As a commonly used component for external cavity locking, the volume grating (VBG) is greatly affected by its own processing accuracy and temperature during external cavity locking. There are deviations in the etching accuracy of the individual gratings, and this deviation will lead to certain deviations in the center wavelength, half-maximum width (FWHM), etc. When multiple chips are individually locked in a fiber coupling module, there will be certain deviations in each locking channel, and the cumulative deviation will be relatively large, resulting in a larger linewidth of the final fiber coupling output. Taking the 878 product as an example, if the center wavelength at the working current after locking is required to be 878.6±1nm, and the half-maximum width (FWHM) is less than 0.5nm, the half-width of the volume grating (VBG) provided by the supplier can meet the requirements in most cases, but the center wavelength range is relatively wide, generally in the range of 1-2nm, and the wavelength will be uncertain in the case of multi-channel superposition. Assuming the center wavelengths of VBG1 and VBG2 are 878.1 and 878.9, respectively, with a FWHM of 0.5 nm, the center wavelength after superposition is exactly 878.5 nm. However, the full width at half maximum (FWHM) is close to 1 nm, and two obvious peaks will appear. In this case, VBG1 and VBG2 need to be disassembled, re-locked, and retested, which is time-consuming, labor-intensive, and costly. Summary of the Invention

[0006] In response to the above problems, the present application provides a semiconductor laser external cavity locked volume grating screening device and screening method, which can screen the volume grating, thereby eliminating the steps of repeated rework and testing, reducing costs, improving efficiency, and enhancing product yield and product quality.

[0007] The technical solution adopted by the present invention to solve the technical problem is:

[0008] A semiconductor laser external cavity wave-locked bulk grating screening device comprises a chip, wherein a fast axis collimator, a slow axis collimator and a laser beam splitter are sequentially arranged on the light emitting side of the chip along the light emitting direction;

[0009] A first test bench is provided between the fast axis collimator and the slow axis collimator, and a second test bench is provided between the slow axis collimator and the laser beam splitter;

[0010] The transmitted light emitting side of the laser beam splitter is provided with a power meter, and the reflected light emitting side of the laser beam splitter is provided with an attenuation plate and a spectrometer in sequence along the light emitting direction.

[0011] Furthermore, the proportion of the transmitted light of the laser beam splitter is greater than 99%.

[0012] Furthermore, both the first test bench and the second test bench are provided with a heating element for heating the grating of the object to be tested.

[0013] A method for screening a semiconductor laser external cavity wave-locked bulk grating comprises the following steps:

[0014] S1, placing the volume grating to be tested on a first test bench or a second test bench according to the usage scenario of the volume grating;

[0015] S2, testing the volume grating to be tested;

[0016] 2.1 Determine the current test range (A min , A max ), where A min is the threshold current of the chip, A max is the maximum operating current of the chip;

[0017] 2.2 Test power loss;

[0018] 2.2.1 In the range (A min , A max ), select N test currents;

[0019] 2.2.2 Adjust the current and record the power value under the corresponding test current;

[0020] 2.2.3 Place the volume grating to be tested on the test bench determined in step S1;

[0021] 2.2.4 Adjust the current and record the power value under the corresponding test current;

[0022] 2.2.5 According to the formula

[0023]

[0024] Where: η is the power loss rate;

[0025] D is the lock wavefront power;

[0026] VD is the power after wave locking;

[0027] Calculate the power loss rate of the tested grating under different test currents, and take the maximum value as the final power loss rate of the tested grating;

[0028] 2.3 Test the locking current range under different wavelength drift coefficients;

[0029] 2.3.1 Adjust the current and record the central wavelength at the corresponding current;

[0030] 2.3.2 Set the wavelength drift coefficient to C1 and substitute the data obtained in step 2.3.1 into the formula

[0031]

[0032] Where: C represents the wavelength drift coefficient, the unit is nm / A;

[0033] λy represents the wavelength when the current is A2y, in nm;

[0034] λx represents the wavelength when the current is A2x, in nm;

[0035] Calculate the current range that satisfies the wavelength drift coefficient C1, and take the maximum current range as the wave-locking current range when the wavelength drift coefficient is C1;

[0036] 2.3.3 Set the wavelength drift coefficient to C2 and repeat step 2.3.2 to obtain the locking current range when the wavelength drift coefficient is C2;

[0037] 2.3.4 Set the wavelength drift coefficient to C3 and repeat step 2.3.2 to obtain the locking current range when the wavelength drift coefficient is C3.

[0038] Furthermore, in step 2.3.1, when adjusting the current, the minimum current is less than the threshold current A of the chip. min , the maximum current is greater than the maximum operating current A of the chip max .

[0039] Furthermore, in step 2.2.1, at least three test currents are selected, wherein the test currents include a threshold current A min and maximum operating current A max .

[0040] Furthermore, step S2 further includes,

[0041] 2.4 Test the locking temperature range under different wavelength drift coefficients;

[0042] 2.4.1 Adjust the temperature of the grating under test by controlling the heating element and record the central wavelength at the corresponding temperature;

[0043] 2.4.2 Set the wavelength drift coefficient to C1′ and substitute the data obtained in step 2.4.1 into the formula

[0044]

[0045] Where: C' represents the wavelength drift coefficient, the unit is nm / ℃;

[0046] λy′ represents the wavelength when the temperature is Ty, in nm;

[0047] λx′ represents the wavelength when the temperature is Tx, in nm;

[0048] Calculate the temperature range that satisfies the wavelength drift coefficient C1′, and take the maximum temperature range as the wave-locking temperature range when the wavelength drift coefficient is C1′;

[0049] 2.4.3 Set the wavelength drift coefficient to C2′ and repeat step 2.4.2 to obtain the wavelength locking temperature range when the wavelength drift coefficient is C2′;

[0050] 2.4.4 Set the wavelength drift coefficient to C3′ and repeat step 2.4.2 to obtain the wavelength locking temperature range when the wavelength drift coefficient is C3′.

[0051] Furthermore, the value of the wavelength drift coefficient C1 is 0nm / A, the value of the wavelength drift coefficient C2 is 0.01nm / A, the value of the wavelength drift coefficient C3 is 0.02nm / A, the value of the wavelength drift coefficient C1′ is 0nm / ℃, the value of the wavelength drift coefficient C2′ is 0.01nm / ℃, and the value of the wavelength drift coefficient C3′ is 0.02nm / ℃.

[0052] Furthermore, in step 2.4.1 of this embodiment, the temperature adjustment range of the grating to be measured is 10°C-40°C.

[0053] The beneficial effects of the present invention are:

[0054] The embodiments of the present application provide a semiconductor laser external cavity locked volume grating screening device and screening method, which pre-screen the volume grating by testing the power loss rate and the locking current range under different wavelength drift coefficients, and provide data support for the selection and use of the volume grating in the later stage. It can ensure that the final fiber-coupled output linewidth is maintained at a relatively narrow level and that the central wavelength can be determined before production, eliminating the steps of repeated rework and testing, reducing costs, improving the consistency and production efficiency of the entire product, and also improving the product yield and product quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Figure 1 A schematic diagram of the principle of a semiconductor laser external cavity wave-locked body grating screening device provided in an embodiment of the present application.

[0056] In the figure: 1. Chip; 2. Fast-axis collimator; 3. Slow-axis collimator; 4. Laser beam splitter; 5. First test bench; 6. Second test bench; 7. Power meter; 8. Attenuator; 9. Spectrometer. DETAILED DESCRIPTION

[0057] In order to enable those skilled in the art to better understand the technical solutions in this application, the technical solutions in the embodiments of this application will be described in detail below in conjunction with the drawings in the embodiments of this application. The described embodiments are only part of the embodiments of this application, not all of the embodiments. All other embodiments obtained by those skilled in the art without creative work based on the embodiments of this application should fall within the scope of protection of this application.

[0058] like Figure 1 As shown, a semiconductor laser external cavity locked body grating screening device includes a chip 1. A fast axis collimator 2, a slow axis collimator 3, and a laser beam splitter 4 are sequentially arranged on the light-emitting side of the chip 1 along the light-emitting direction. A first test bench 5 for supporting the body grating is arranged between the fast axis collimator 2 and the slow axis collimator 3, and a second test bench 6 for supporting the body grating is arranged between the slow axis collimator 3 and the laser beam splitter 4. The laser beam splitter 4 is used to split the laser into two beams, one beam passing through the laser beam splitter 4 and the other beam reflected by the laser beam splitter 4. A power meter 7 is provided on the transmitted light emitting side of the laser beam splitter 4. The power meter 7 is used to measure the optical power of the portion of the transmitted light that passes through the laser beam splitter 4. An attenuator 8 and a spectrometer 9 are sequentially arranged on the reflected light emitting side of the laser beam splitter 4 along the light-emitting direction. The spectrometer 9 is used to detect the center wavelength and half-maximum width of the portion of the reflected light reflected by the laser beam splitter 4.

[0059] Furthermore, the proportion of transmitted light passing through the laser beam splitter 4 is greater than 99%, and correspondingly, the proportion of reflected light passing through the laser beam splitter 4 is less than 1%. As a specific implementation, in this embodiment, the reflection and transmittance ratios can be achieved by coating the optical glass.

[0060] Because the spectrometer 9 cannot receive too much energy, an attenuation plate 8 is provided to attenuate the light energy. Preferably, the attenuation plate 8 is an adjustable attenuation plate 8, thereby continuously adjusting the power of the light incident on the spectrometer 9. The adjustable attenuation plate 8 is known from the prior art, and its specific structure will not be further described here.

[0061] Furthermore, both the first test bench 5 and the second test bench 6 are provided with a heating element (not shown in the figures), and the heating element is used to heat the volume grating to be tested.

[0062] As a specific embodiment, the heating element described in this embodiment adopts a semiconductor temperature control module. The semiconductor temperature control module is arranged below the first test platform 5 and the second test platform 6, and transfers heat to the first test platform 5 and the second test platform 6 by contact heat transfer, thereby heating the volume grating placed on the first test platform 5 and the second test platform 6. The first test platform 5 and the second test platform 6 are made of thermally conductive material.

[0063] A method for screening a semiconductor laser external cavity wave-locked bulk grating comprises the following steps:

[0064] S1 , placing the volume grating to be tested on the first test bench 5 or the second test bench 6 according to the usage scenario of the volume grating.

[0065] If the volume grating to be tested is placed between the fast-axis collimator 2 and the slow-axis collimator 3 during normal use, the volume grating to be tested is placed on the first test bench 5; if the volume grating to be tested is placed on the light-emitting side of the slow-axis collimator 3 during normal use, the volume grating to be tested is placed on the second test bench 6.

[0066] S2, testing the volume grating to be tested.

[0067] 2.1 Determine the current test range (A min , A max ), where A min is the threshold current of chip 1, A max is the maximum operating current of chip 1.

[0068] 2.2 Test power loss.

[0069] 2.2.1 The interval range (A min , A max), select N test currents, namely A11, A12...A1n.

[0070] 2.2.2 Turn on the power supply and adjust the current so that the currents passing through chip 1 are A11, A12, ..., A1n in sequence. Record the power values ​​D1, D2, ..., Dn measured by the power meter 7 under the corresponding test currents.

[0071] 2.2.3 Place the volume grating to be tested on the test bench determined in step S1.

[0072] 2.2.4 Turn on the power supply and adjust the current so that the currents passing through chip 1 are A11, A12, ..., A1n in sequence. Record the power values ​​VD1, VD2, ..., VDn measured by the power meter 7 at the corresponding test currents.

[0073] 2.2.5 According to the formula

[0074]

[0075] Where: η is the power loss rate;

[0076] D is the lock wavefront power;

[0077] VD is the power after wave locking;

[0078] Calculate the power loss rates η1, η2, ..., ηn of the tested volume grating under different test currents, and take the maximum value as the final power loss rate of the tested volume grating.

[0079] The significance of testing the power loss of volume gratings is that by testing the power loss rate of volume gratings, it is convenient to put modules into production according to different power loss rates. For example, when there are higher electro-optical efficiency requirements, volume gratings with a lower power loss rate can be put into production. If the product requires low electro-optical conversion efficiency, a volume grating with a higher power loss rate can be selected.

[0080] Furthermore, in step 2.2.1, at least three test currents are selected, and the test currents must include a threshold current A. min and maximum operating current A max , and the test current is evenly distributed within the current test range determined in step 2.1.

[0081] 2.3 Test the locking current range under different wavelength drift coefficients.

[0082] 2.3.1 Turn on the power supply and adjust the current so that the current passing through chip 1 is A21, A22, ..., A2n in sequence. Record the central wavelengths λ1, λ2, ..., λn measured by spectrometer 9 at the corresponding currents.

[0083] As a specific implementation, in this embodiment, the difference between two adjacent currents in A21, A22, ..., A2n is 1A.

[0084] 2.3.2 Set the wavelength drift coefficient to C1 and substitute the data obtained in step 2.3.1 into the formula

[0085]

[0086] Where: C represents the wavelength drift coefficient, the unit is nm / A;

[0087] λy represents the wavelength when the current is A2y, in nm;

[0088] λx represents the wavelength when the current is A2x, in nm;

[0089] The current range that satisfies the wavelength drift coefficient C1 is calculated, and the maximum current range is taken as the wave-locking current range when the wavelength drift coefficient is C1.

[0090] Since the center wavelength generally changes in a pulsed manner as the current increases, that is, when the current is too large or too small, the center wavelength will deteriorate sharply, while within a certain current range, the center wavelength changes relatively little. Therefore, the locking current range under the corresponding wavelength drift coefficient can be obtained by substituting the data obtained in step 2.3.1 into the verification method.

[0091] 2.3.3 Set the wavelength drift coefficient to C2 and repeat step 2.3.2 to obtain the locking current range when the wavelength drift coefficient is C2.

[0092] 2.3.4 Set the wavelength drift coefficient to C3 and repeat step 2.3.2 to obtain the locking current range when the wavelength drift coefficient is C3.

[0093] As a specific implementation, in this embodiment, the value of the wavelength drift coefficient C1 is 0 nm / A, the value of the wavelength drift coefficient C2 is 0.01 nm / A, and the value of the wavelength drift coefficient C3 is 0.02 nm / A.

[0094] Furthermore, the value of the current A21 is less than the threshold current A of the chip 1. min Preferably, the value of current A21 is 0A. The value of current A2n is greater than the maximum operating current A of chip 1. max .

[0095] 2.4 Test the locking temperature range under different wavelength drift coefficients.

[0096] 2.4.1 Turn on the power supply and keep the current constant. Control the heating element to adjust the temperature of the grating to T1, T2, ..., Tn in sequence. Record the central wavelengths λ1', λ2', ..., λn' measured by the spectrometer 9 at the corresponding temperatures.

[0097] As a specific implementation, in this embodiment, the difference between two adjacent temperatures among T1, T2, ..., Tn is 1°C.

[0098] 2.4.2 Set the wavelength drift coefficient to C1′ and substitute the data obtained in step 2.4.1 into the formula

[0099]

[0100] Where: C' represents the wavelength drift coefficient, the unit is nm / ℃;

[0101] λy′ represents the wavelength when the temperature is Ty, in nm;

[0102] λx′ represents the wavelength when the temperature is Tx, in nm;

[0103] The temperature range that satisfies the wavelength drift coefficient C1′ is calculated, and the maximum temperature range is taken as the wave-locking temperature range when the wavelength drift coefficient is C1′.

[0104] Since the central wavelength generally changes in a pulsed manner as the temperature increases, that is, when the temperature is too high or too low, the central wavelength will deteriorate sharply, while within a certain temperature range, the central wavelength changes relatively little. Therefore, the locking temperature range under the corresponding wavelength drift coefficient can be obtained by substituting the data obtained in step 2.4.1 into the verification method.

[0105] 2.4.3 Set the wavelength drift coefficient to C2′ and repeat step 2.4.2 to obtain the wavelength locking temperature range when the wavelength drift coefficient is C2′.

[0106] 2.4.4 Set the wavelength drift coefficient to C3′ and repeat step 2.4.2 to obtain the wavelength locking temperature range when the wavelength drift coefficient is C3′.

[0107] As a specific implementation, in this embodiment, the value of the wavelength drift coefficient C1′ is 0 nm / °C, the value of the wavelength drift coefficient C2′ is 0.01 nm / °C, and the value of the wavelength drift coefficient C3′ is 0.02 nm / °C.

[0108] As a specific implementation, the temperature in step 2.4.1 of this embodiment ranges from 10°C to 40°C.

[0109] Other embodiments obtained by those skilled in the art by combining, splitting, reorganizing, etc. the embodiments provided in this application do not exceed the scope of protection of this application.

[0110] The above specific implementation methods provide a detailed description of the purpose, technical solutions and beneficial effects of the embodiments of the present application. The above is only a specific implementation method of the embodiments of the present application and is not intended to limit the scope of protection of the embodiments of the present application. That is, any modifications, equivalent replacements, improvements, etc. made on the basis of the embodiments of the present application should be included in the scope of protection of the embodiments of the present application.

Claims

1. A semiconductor laser external cavity wave-locked bulk grating screening device, characterized by: It comprises a chip (1), wherein a fast axis collimator (2), a slow axis collimator (3) and a laser beam splitter (4) are sequentially arranged on the light-emitting side of the chip (1) along the light-emitting direction; A first test bench (5) is provided between the fast-axis collimator (2) and the slow-axis collimator (3), and a second test bench (6) is provided between the slow-axis collimator (3) and the laser beam splitter (4); The transmitted light emitting side of the laser beam splitter (4) is provided with a power meter (7), and the reflected light emitting side of the laser beam splitter (4) is provided with an attenuation plate (8) and a spectrometer (9) in sequence along the light emitting direction.

2. The semiconductor laser external cavity wave-locked bulk grating screening device according to claim 1, characterized in that: The proportion of light transmitted by the laser beam splitter (4) is greater than 99%.

3. The semiconductor laser external cavity wave-locked bulk grating screening device according to claim 1, characterized in that: The first test bench (5) and the second test bench (6) are both provided with heating elements for heating the grating of the object to be tested.

4. A screening method for the semiconductor laser external cavity wave-locked bulk grating screening device according to claim 3, characterized in that: The following steps are included: S1, placing the volume grating to be tested on a first test bench (5) or a second test bench (6) according to the usage scenario of the volume grating; S2, testing the volume grating to be tested; 2.1 Determine the current test range (A min , A max ), where A min is the threshold current of chip (1), A max is the maximum operating current of the chip (1); 2.2 Test power loss; 2.2.1 In the range (A min , A max ), select N test currents; 2.2.2 Adjust the current and record the power value under the corresponding test current; 2.2.3 Place the volume grating to be tested on the test bench determined in step S1; 2.2.4 Adjust the current and record the power value under the corresponding test current; 2.2.5 According to the formula Where: η is the power loss rate; D is the lock wavefront power; VD is the power after wave locking; Calculate the power loss rate of the tested grating under different test currents, and take the maximum value as the final power loss rate of the tested grating; 2.3 Test the locking current range under different wavelength drift coefficients; 2.3.1 Adjust the current and record the central wavelength at the corresponding current; 2.3.2 Set the wavelength drift coefficient to C1 and substitute the data obtained in step 2.3.1 into the formula Where: C represents the wavelength drift coefficient, the unit is nm / A; λy represents the wavelength when the current is A2y, in nm; λx represents the wavelength when the current is A2x, in nm; Calculate the current range that satisfies the wavelength drift coefficient C1, and take the maximum current range as the wave-locking current range when the wavelength drift coefficient is C1; 2.3.3 Set the wavelength drift coefficient to C2 and repeat step 2.3.2 to obtain the locking current range when the wavelength drift coefficient is C2; 2.3.4 Set the wavelength drift coefficient to C3 and repeat step 2.3.2 to obtain the locking current range when the wavelength drift coefficient is C3.

5. The method for screening a semiconductor laser external cavity wave-locked bulk grating according to claim 4, characterized in that: In step 2.3.1, when adjusting the current, the minimum current is less than the threshold current A of the chip (1) min , the maximum current is greater than the maximum operating current A of the chip (1) max .

6. The method for screening a semiconductor laser external cavity wave-locked bulk grating according to claim 4, characterized in that: In step 2.2.1, at least three test currents are selected, wherein the test current includes a threshold current A. min and maximum operating current A max .

7. The method for screening a semiconductor laser external cavity wave-locked bulk grating according to claim 4, characterized in that: Step S2 also includes, 2.4 Test the locking temperature range under different wavelength drift coefficients; 2.4.1 Adjust the temperature of the grating under test by controlling the heating element and record the central wavelength at the corresponding temperature; 2.4.2 Set the wavelength drift coefficient to C1′ and substitute the data obtained in step 2.4.1 into the formula Where: C' represents the wavelength drift coefficient, the unit is nm / ℃; λy′ represents the wavelength when the temperature is Ty, in nm; λx′ represents the wavelength when the temperature is Tx, in nm; Calculate the temperature range that satisfies the wavelength drift coefficient C1′, and take the maximum temperature range as the wave-locking temperature range when the wavelength drift coefficient is C1′; 2.4.3 Set the wavelength drift coefficient to C2′ and repeat step 2.4.2 to obtain the wavelength locking temperature range when the wavelength drift coefficient is C2′; 2.4.4 Set the wavelength drift coefficient to C3′ and repeat step 2.4.2 to obtain the wavelength locking temperature range when the wavelength drift coefficient is C3′.

8. The method for screening a semiconductor laser external cavity wave-locked bulk grating according to claim 7, characterized in that: The value of the wavelength drift coefficient C1 is 0nm / A, the value of the wavelength drift coefficient C2 is 0.01nm / A, the value of the wavelength drift coefficient C3 is 0.02nm / A, the value of the wavelength drift coefficient C1′ is 0nm / °C, the value of the wavelength drift coefficient C2′ is 0.01nm / °C, and the value of the wavelength drift coefficient C3′ is 0.02nm / °C.

9. The method for screening a semiconductor laser external cavity wave-locked bulk grating according to claim 7, characterized in that: In step 2.4.1 of this embodiment, the temperature adjustment range of the grating to be measured is 10°C-40°C.

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