Return light testing system and testing method for laser device

Abstract

Provided in the present disclosure are a return light testing system and testing method for a laser device. The return light testing system sequentially comprises, in a transmission direction of laser emitted by a laser device, a return light energy adjustment unit and a reflector, wherein the return light energy adjustment unit adjusts the light intensity of return light until the laser device fails, so as to determine a return light resistance threshold of the laser device. In the present disclosure, the reflector is used to form the return light. On one hand, no interference or influence is introduced to laser transmitted in an optical path; on the other hand, the wavelength of the return light is synchronized with that of the emitted light in real time. Therefore, the influence of the return light on the laser device during usage can be realistically simulated, the return light resistance capability of the laser device during actual usage can be measured, and the measurement accuracy is very high.

Description

A laser return light testing system and method

[0001] Cross-reference to related applications

[0002] This disclosure claims priority to Chinese Patent Application No. 2025103768919, filed on March 28, 2025, entitled "A Laser Backlight Testing System and Testing Method", the entire contents of which are incorporated herein by reference. Technical Field

[0003] This disclosure relates to the field of semiconductor laser technology, and more specifically, to a laser backlight testing system and testing method. Background Technology

[0004] The front cavity surface of a laser is coated with an optical film. Due to the reversibility of the optical path, some light beams are reflected back to the front cavity surface of the laser when no isolators or other devices are added in the optical path. The optical film is extremely sensitive to temperature; absorption of the reflected light by the optical film leads to an increase in the film temperature, thereby lowering the COMD (Catastrophic Optical Mirror Damage) threshold of the laser's front cavity surface film. This causes premature failure of the original design structure and reduces the reliability of the laser. Therefore, testing the laser's resistance to reflected light is essential.

[0005] Common laser backlight capability testing systems include the following two types:

[0006] (1) A return optical path is constructed using an optical fiber structure, and the laser emitted from the light source is returned to the output cavity surface through the optical fiber. When the laser emitted from the front cavity surface of the laser is coupled into the optical fiber, there is edge loss. In addition, the beam is shaped and rotated during transmission in the optical fiber, and the bending of the optical fiber can cause abnormal return light. Therefore, the return optical path is constructed using an optical fiber. However, due to the above-mentioned effects of the optical fiber itself, the return light cannot accurately simulate the effect of the return light on the chip cavity surface during the actual use of the laser, resulting in insufficient measurement accuracy.

[0007] On the other hand, optical fibers can only carry relatively low power. For lasers with high output power, such as lasers with an output power of around 100W, the output power exceeds the power range that optical fibers can carry to transmit beams, making it impossible to use optical fibers for coupling transmission and measurement of anti-return light capability.

[0008] (2) Introducing external light as a light source to simulate reflected light is problematic because optical films are sensitive to light wavelength, and each laser experiences random wavelength drift due to its own heat dissipation during operation. Even if a laser of the same wavelength is introduced as external light, the difference in heat dissipation and temperature drift during operation makes it impossible to simulate and reproduce the wavelength of the laser under test in real time. Therefore, introducing an external laser cannot simulate the real-time effects of reflected light on the laser under test during actual use.

[0009] Therefore, existing technologies cannot accurately simulate the reflected light experienced by a laser during use, thus making it impossible to precisely measure the laser's resistance to reflected light during use. Summary of the Invention

[0010] This disclosure provides a laser backlight testing system and method. The backlight testing system, along the laser transmission direction emitted from the laser, includes, in sequence: a backlight energy adjustment unit and a reflector.

[0011] The reflector is disposed in the propagation path of the laser and configured to reflect the laser to form a return light, and to incident the return light onto the active region of the laser.

[0012] The backlight energy adjustment unit is located in the propagation path of the backlight and is configured to adjust the intensity of the backlight until the laser fails, so as to determine the anti-backlight threshold of the laser.

[0013] Optionally, the reflected light energy adjustment unit includes a half-wave plate and a polarizing beam splitter arranged sequentially along the laser transmission direction. The polarizing beam splitter adjusts the intensity of the reflected light by adjusting the rotation angle of the half-wave plate.

[0014] Optionally, the return light energy adjustment unit further includes a power meter, and the polarizing beam splitter splits the return light into two beams. One beam passes through the polarizing beam splitter and is incident on the active region of the laser, while the other beam is reflected by the polarizing beam splitter and enters the power meter.

[0015] Optionally, the retroreflection testing system further includes a wedge mirror, which is positioned in front of the retroreflection energy adjustment unit along the laser transmission direction. Along the laser transmission direction, the wedge mirror includes an incident surface and an exit surface in sequence. The laser beam emitted from the laser is refracted by the wedge mirror and exits from the exit surface before entering the retroreflection energy adjustment unit.

[0016] Optionally, the reflected light testing system further includes a near-field imaging unit located on the exit surface of the wedge mirror. The laser passes through the wedge mirror, is reflected back to the incident surface by the exit surface of the wedge mirror, and then exits through the exit surface before entering the near-field imaging unit.

[0017] Optionally, the reflected light testing system further includes a spectrometer; the spectrometer is located on one side of the incident surface of the wedge mirror, and the light beam emitted by the laser is reflected by the incident surface of the wedge mirror into the spectrometer.

[0018] Optionally, the reflected light testing system further includes an adjustment device configured to adjust the position and angle of the reflector until the reflected light is reflected by the reflector and then incident on the active region of the laser through the reflected light energy adjustment unit.

[0019] Another aspect of this disclosure provides a method for testing the reflected light of a laser, the method comprising:

[0020] Provide a laser;

[0021] An excitation is applied to the laser, causing the laser emitted by the laser to be reflected back into the active region of the laser by the laser reflection test system described above;

[0022] The intensity of the returned light is adjusted by the returned light energy adjustment unit until the laser fails, so as to determine the anti-return light threshold of the laser.

[0023] Optionally, the intensity of the returned light is adjusted by the returned light energy adjustment unit until the laser fails, in order to determine the anti-return light threshold of the laser, including: rotating the half-wave plate of the laser's returned light test system to a preset rotation angle, gradually increasing the excitation of the laser until the laser fails, obtaining the half-wave plate rotation angle and excitation corresponding to the laser failure; and determining the anti-return light threshold of the laser based on the half-wave plate rotation angle and the excitation.

[0024] Optionally, if the laser does not fail even when the excitation is increased to the maximum value, the rotation angle of the half-wave plate is adjusted to increase the intensity of the reflected light until the laser fails; the anti-reflection threshold of the laser is determined based on the rotation angle of the half-wave plate and the excitation.

[0025] Optionally, applying excitation to the laser, causing the laser emitted by the laser to be reflected back into the active region of the laser via the laser reflection test system described above, includes: applying excitation to the laser, coarsely adjusting the reflector by adjusting its position and angle, while simultaneously observing the near-field image on the near-field imaging unit; when a sudden brightness change is observed in the near-field image, the reflected back has been incident near the active region of the laser, and fixing the reflector; finely adjusting the reflector by adjusting its position and angle, and acquiring the power change trend of the power meter; when the power meter reading reaches its maximum value, the reflected back is precisely incident on the active region of the laser, and fixing the position of the reflector.

[0026] Optionally, the stimulus is 20%-80% of the threshold stimulus.

[0027] This disclosure provides a laser return light testing system and method, which have the following technical advantages:

[0028] (1) The laser backlight test system and test method disclosed herein use a reflector to form backlight. On the one hand, the reflector will not interfere with or affect the laser transmitted in the optical path. On the other hand, the wavelength of the backlight is synchronized with the wavelength of the emitted light in real time. Therefore, the influence of backlight during the use of the laser can be simulated in a real way, and the anti-backlight capability of the laser during real use can be measured with very high measurement accuracy.

[0029] (2) The laser backlight testing system and testing method disclosed herein use a reflector to form backlight. Since the reflector does not interfere with or affect the laser transmitted in the optical path, the intensity distribution of the backlight on the front cavity surface is the same as that of the outgoing light on the cavity surface. The intensity distribution of the outgoing light can be obtained by the intensity distribution of the backlight on the front cavity surface, and the intensity distribution of the semiconductor front cavity surface can be further judged, such as whether there are any points with abnormal intensity distribution. Based on this, the laser can be optimized in the future. Attached Figure Description

[0030] To more clearly illustrate the technical solutions of the embodiments of this disclosure, the accompanying drawings used in the embodiments of this disclosure will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this disclosure and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0031] Figure 1 is a structural diagram of the laser return light test system of this disclosure;

[0032] Figure 2(a) is a schematic diagram of the near-field image (I);

[0033] Figure 2(b) is a schematic diagram of the near-field image (II);

[0034] Figure 3 shows the relationship between the rotation angle of the half-wave plate and the proportion of the reflected light to the intensity of the laser light emitted by the laser.

[0035] Figure 4 is a flowchart illustrating the laser backlight testing method disclosed herein.

[0036] In the figure, 1. Laser, 2. Fast-axis collimating lens, 3. Slow-axis collimating lens, 4. Wedge mirror, 5. Half-wave plate, 6. Polarizing beam splitter, 7. Mirror, 8. Power meter, 9. Spectrometer, 10. Converging lens, 11. Near-field imaging unit, 12. Incident surface, 13. Exit surface. Detailed Implementation

[0037] The technical solutions of the embodiments of this disclosure will now be described with reference to the accompanying drawings.

[0038] This embodiment provides a laser backlight testing system, as shown in Figure 1, which includes, in sequence along the laser transmission direction emitted from the laser 1: a backlight energy adjustment unit and a reflector 7.

[0039] The laser emitted from laser 1 enters the return light energy adjustment unit and is incident on reflector 7.

[0040] The reflector 7 reflects the incident laser light to form a backlight, the purpose of which is to ensure that the backlight returns to the active region of the laser 1. Before returning to the laser 1, the backlight passes through the backlight energy adjustment unit and then is incident on the laser 1. The backlight energy adjustment unit can adjust the intensity of the backlight until the laser 1 fails, thereby determining the backlight resistance threshold of the laser 1.

[0041] This embodiment provides a laser backlight testing system, as shown in Figure 1. Along the laser transmission direction emitted from the laser 1, it includes, in sequence: a wedge mirror 4, a backlight energy adjustment unit and a reflector 7, as well as an adjustment device.

[0042] The laser beam emitted from laser 1 passes through fast-axis collimating lens 2 and slow-axis collimating lens 3 and is incident on wedge mirror 4. Along the laser transmission direction, wedge mirror 4 includes an incident surface 12 and an exit surface 13. The laser beam emitted from laser 1 enters wedge mirror 4 from incident surface 12, is refracted by wedge mirror 4, and exits from exit surface 13 before entering the return light energy adjustment unit.

[0043] The reflector 7 is configured to reflect the laser to form backlight, and the adjustment device is configured to adjust the position and angle of the reflector 7 so that the backlight is reflected by the reflector 7 to the active region of the laser 1. The backlight energy adjustment unit is configured to adjust the intensity of the backlight until the laser 1 fails, in order to determine the backlight resistance threshold of the laser 1.

[0044] The reflected light energy adjustment unit includes a half-wave plate 5 and a polarizing beam splitter 6 arranged sequentially along the laser transmission direction. The polarizing beam splitter 6 adjusts the intensity of the reflected light by adjusting the rotation angle of the half-wave plate 5. Optionally, the reflected light energy adjustment unit also includes a power meter 8. The polarizing beam splitter 6 splits the reflected light into two beams. One beam passes through the polarizing beam splitter 6 and is incident on the active region of the laser 1. The other beam is reflected by the polarizing beam splitter 6 and enters the power meter 8. The power meter 8 is configured to measure the intensity of the beam reflected by the polarizing beam splitter 6.

[0045] Optionally, the reflected light testing system further includes a near-field imaging unit 11. The near-field imaging unit 11 is configured to determine the near-field image of the laser emitted from the laser 1. The near-field imaging unit 11 is located on one side of the exit surface 13 of the wedge mirror 4. The laser passes through the wedge mirror 4, is reflected back to the incident surface 12 by the exit surface 13 of the wedge mirror 4, and then exits through the exit surface 13 before entering the near-field imaging unit 11. A converging lens 10 can be added before the near-field imaging unit 11 so that the near-field image of the laser is imaged onto the near-field imaging unit 11 after passing through the converging lens 10.

[0046] Optionally, the backlight testing system also includes a spectrometer 9, which is configured to determine the wavelength of the laser emitted by the laser 1 in order to determine the anti-backlight threshold at a specific wavelength emitted by the laser 1. The spectrometer 9 is located on one side of the incident surface 12 of the wedge mirror 4, and the beam emitted by the laser 1 is reflected by the incident surface 12 of the wedge mirror 4 into the spectrometer 9.

[0047] As shown in Figure 4, the method for testing the returned light of laser 1 based on the returned light testing system provided in this disclosure includes:

[0048] Excitation is applied to laser 1, so that the laser emitted by laser 1 is reflected back by the return light test system and incident on the active region of laser 1;

[0049] The intensity of the returned light is adjusted by the returned light energy adjustment unit until the laser 1 fails, so as to determine the anti-return light threshold of the laser 1.

[0050] Optionally, applying excitation to the laser 1, causing the laser emitted by the laser 1 to form a reflected light incident on the active region of the laser 1 via the reflected light testing system, includes the following two steps:

[0051] Step (1): Apply excitation to laser 1 and coarsely adjust mirror 7 so that the reflected light is incident near the active region of laser 1, as shown in Figure 2(a).

[0052] Specifically, by adjusting the position and angle of the reflector 7, a near-field image on the near-field imaging unit 11 is acquired. When a sudden change in brightness occurs in the near-field image, it indicates that the reflected light has been incident near the active region of the laser 1. The reason for this is that, in addition to the electrical excitation of the laser 1 itself, the reflected light can serve as another optical excitation for the laser 1. When the reflected light is incident near the active region of the laser 1 by adjusting the reflector 7, the reflected light can then act as another optical excitation on the laser 1 itself, causing the formation of a particle beam that reverses and emits laser light. Therefore, a sudden change in brightness can be observed in the near-field image formed by the near-field imaging unit 11, as shown in Figures 2(a) to 2(b).

[0053] In order to observe the brightness change of the near field image in step (1), the electrical excitation applied to the laser 1 is 20%-80% of the threshold current. That is, under the condition of only electrical excitation, no particle beam reversal is formed in the laser 1, no laser is emitted and spontaneous emission of fluorescence is generated. The near field image formed by the near field imaging unit 11 is shown in Figure 2(a).

[0054] Step (2) is to fine-tune the reflector 7 so that the reflected light is accurately incident on the active region of the laser 1.

[0055] Specifically, adjust the position and angle of the reflector 7 and observe the power change trend of the power meter 8. When the reading of the power meter 8 reaches its maximum value, it indicates that the reflected light has been accurately incident on the active region of the laser 1. That is, most of the energy of the reflected light has been applied to the laser 1 as optical excitation, and the optical excitation applied to the laser 1 has reached its maximum value. Therefore, the laser intensity emitted by the laser 1 reaches its maximum value, and the intensity of the reflected light in the optical path is also the maximum. Fix the position and angle of the reflector 7 at this time.

[0056] The method for determining the maximum value of the power meter 8 reading may include, but is not limited to, determining the maximum value based on the power value measured by the power meter 8 in the nth measurement, the power value measured in the (n-1)th measurement, and the power value measured in the (n+1)th measurement; during the adjustment of the position and angle of the reflector 7, it is always ensured that the power value measured in the nth measurement is greater than the power value measured in the (n-1)th measurement, and when the power value measured in the nth measurement is greater than the power value measured in the (n+1)th measurement, then the power value measured by the power meter 8 in the nth measurement is determined to be the maximum value.

[0057] Optionally, the intensity of the returned light is adjusted by the returned light energy adjustment unit until the laser 1 fails, in order to determine the anti-return light threshold of the laser 1, including:

[0058] Rotate the half-wave plate 5 to a preset rotation angle, gradually increase the electrical excitation of the laser 1 until the laser 1 fails, and obtain the rotation angle and electrical excitation of the half-wave plate 5 corresponding to the failure of the laser 1; determine the anti-backlight threshold of the laser 1 based on the rotation angle of the half-wave plate 5 and the electrical excitation of the laser 1.

[0059] If the laser 1 does not fail even when the electrical excitation is increased to the maximum value, the rotation angle of the half-wave plate 5 is adjusted to increase the intensity of the reflected light until the laser 1 fails. The relationship between the rotation angle of the half-wave plate 5 and the optical feedback intensity curve of the reflected light is shown in Figure 3. The anti-reflection threshold of the laser 1 is determined based on the rotation angle of the half-wave plate 5 and the electrical excitation of the laser.

[0060] Specifically, the greater the excitation applied to the laser, the higher the power of the laser emitted by the laser (i.e., the higher the power of the reflected light). By adjusting the rotation angle of the half-wave plate 5, the light intensity of the beam returning to the active region of the laser 1 can be adjusted. That is, by adjusting the half-wave plate 5, a certain proportion of the light intensity of the laser emitted by the laser 1 can be returned to the active region of the laser 1. Figure 3 shows the relationship between the rotation angle of the half-wave plate 5 and the proportion of the reflected light to the light intensity of the laser emitted by the laser 1. Optionally, the anti-reflection threshold of the laser 1 can be determined based on the proportion and the light intensity of the laser emitted by the laser 1.

[0061] Specifically, in this embodiment, the principle of adjusting the returned light energy using a half-wave plate 5 and a polarizing beam splitter 6 is as follows: The half-wave plate 5 has two principal axes, namely a fast axis and a slow axis, with different refractive indices, resulting in different light speeds. The angle between the polarization direction of the outgoing light and the polarization direction of the incident light is twice the angle between the polarization direction of the incident light and the principal axis of the wave plate. When the polarization direction of the incident light coincides with either the fast or slow axis, the polarization direction remains unchanged. The half-wave plate 5 can continuously adjust the polarization direction. Assuming the angle between the polarization direction and the slow axis is θ, after the beam passes through the half-wave plate 5, the phase of the light on the fast axis increases by π, resulting in a rotation angle of 2θ for the polarization direction.

[0062] The polarizing beam splitter 6 is an optical element that splits an incident beam into two beams with mutually perpendicular propagation directions. However, unlike ordinary optical beam splitters, the two beams split by it have a special relationship: both beams are linearly polarized, and their polarization directions are perpendicular to each other. In this embodiment, the intensity of the returned light is mainly determined by the returned light energy adjustment unit composed of the half-wave plate 5 and the polarizing beam splitter 6. The intensity of the returned light can be adjusted by adjusting the angle of the half-wave plate 5. The half-wave plate 5 can change the polarization direction of the light, while the polarizing beam splitter 6 allows P-light (parallel polarized light, i.e., light whose electric field vibration direction is parallel to the incident plane, where the incident plane is the plane formed by the incident ray and the normal, and for P-light, its electric vector lies in the incident plane) to pass through, and S-light (perpendicularly polarized light, i.e., light whose electric field vibration direction is perpendicular to the incident plane, and its electric vector is perpendicular to the incident plane) to be reflected. The combination of the two can achieve continuous adjustment of the returned light energy.

[0063] Based on the backlight testing system and method provided in this embodiment, backlight is formed by using the reflector 7. On the one hand, the reflector 7 will not interfere with or affect the laser transmitted in the optical path. On the other hand, the wavelength of the backlight is synchronized with the wavelength of the emitted light in real time. Therefore, the influence of backlight during the use of laser 1 can be realistically simulated, and the anti-backlight capability of laser 1 during actual use can be measured with very high measurement accuracy.

[0064] On the other hand, in this embodiment, the reflector 7 is used to form the reflected light. Since the reflector 7 does not interfere with or affect the laser transmitted in the optical path, the intensity distribution of the reflected light on the front cavity surface of the laser 1 can be simulated by measuring the intensity distribution of the reflected light on the front cavity surface of the laser 1. The intensity distribution of the emitted light can be obtained by measuring the intensity distribution of the reflected light on the front cavity surface, and the intensity distribution of the laser 1 on the front cavity surface can be further judged, such as whether there are any points with abnormal intensity distribution. Based on this, the laser 1 can be optimized in the future.

[0065] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this disclosure, and are not intended to limit them. Although this disclosure has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this disclosure. Industrial applicability

[0066] The laser backlight testing system and method disclosed herein use a reflector to form backlight, which on the one hand will not introduce any interference or influence on the laser transmitted in the optical path, and on the other hand, the wavelength of the backlight is synchronized with the wavelength of the emitted light in real time. Therefore, it can realistically simulate the influence of backlight during the use of the laser, measure the laser's anti-backlight capability in real use, and the measurement accuracy is very high.

Claims

1. A laser return light testing system, characterized in that, The laser transmission direction emitted from the laser includes, in sequence: a return light energy adjustment unit and a reflector; The reflector is disposed in the propagation path of the laser and configured to reflect the laser to form a return light, and to incident the return light onto the active region of the laser. The backlight energy adjustment unit is located in the propagation path of the backlight and is configured to adjust the intensity of the backlight until the laser fails, so as to determine the anti-backlight threshold of the laser.

2. The laser return light testing system as described in claim 1, characterized in that, The return light energy adjustment unit includes a half-wave plate and a polarizing beam splitter arranged sequentially along the laser transmission direction. The polarizing beam splitter adjusts the light intensity of the return light by adjusting the rotation angle of the half-wave plate.

3. The laser return light testing system as described in claim 2, characterized in that, The return light energy adjustment unit also includes a power meter. The polarizing beam splitter splits the return light into two beams. One beam passes through the polarizing beam splitter and is incident on the active region of the laser. The other beam is reflected by the polarizing beam splitter and enters the power meter.

4. The laser return light testing system as described in claim 1, characterized in that, The backlight testing system also includes a wedge mirror, which is positioned in front of the backlight energy adjustment unit along the laser transmission direction; Along the laser transmission direction, the wedge mirror includes an incident surface and an exit surface. The laser beam emitted from the laser is refracted by the wedge mirror and exits from the exit surface before entering the return light energy adjustment unit.

5. The laser return light testing system as described in claim 4, characterized in that, The return light testing system also includes a near-field imaging unit located on the exit surface of the wedge mirror. The laser passes through the wedge mirror, is reflected back to the incident surface by the exit surface of the wedge mirror, and then exits through the exit surface before entering the near-field imaging unit.

6. The laser return light testing system as described in claim 4, characterized in that, The reflected light testing system also includes a spectrometer; the spectrometer is located on one side of the incident surface of the wedge mirror, and the light beam emitted by the laser is reflected by the incident surface of the wedge mirror into the spectrometer.

7. The laser return light testing system as described in claim 1, characterized in that, The reflected light testing system also includes an adjustment device configured to adjust the position and angle of the reflector until the reflected light is reflected by the reflector and then incident on the active region of the laser through the reflected light energy adjustment unit.

8. The laser return light testing system as described in claim 5, characterized in that, The return light testing system also includes a converging lens, which is located between the wedge mirror and the near-field imaging unit.

9. The laser return light testing system as described in claim 1, characterized in that, The return light testing system further includes a fast-axis collimating lens and / or a slow-axis collimating lens, wherein the fast-axis collimating lens and / or the slow-axis collimating lens are located on the light-emitting side of the laser.

10. A method for testing the reflected light of a laser, characterized in that, The method for testing reflected light includes: Provide a laser; An excitation is applied to the laser, causing the laser emitted by the laser to be reflected back into the active region of the laser by the laser reflection test system as described in any one of claims 1 to 9; The intensity of the returned light is adjusted by the returned light energy adjustment unit until the laser fails, so as to determine the anti-return light threshold of the laser.

11. The laser return light testing method as described in claim 10, characterized in that, The intensity of the returned light is adjusted by the returned light energy adjustment unit until the laser fails, in order to determine the anti-return light threshold of the laser, including: Rotate the half-wave plate of the laser backlight test system to a preset rotation angle, gradually increase the excitation of the laser until the laser fails, and obtain the half-wave plate rotation angle and excitation corresponding to the laser failure; determine the anti-backlight threshold of the laser based on the rotation angle of the half-wave plate and the excitation.

12. The laser return light testing method as described in claim 11, characterized in that, If the laser does not fail even when the excitation is increased to the maximum value, the rotation angle of the half-wave plate is adjusted to increase the intensity of the reflected light until the laser fails; the anti-reflection threshold of the laser is determined based on the rotation angle of the half-wave plate and the excitation.

13. The laser return light testing method as described in claim 10, characterized in that, Applying excitation to the laser, causing the laser emitted by the laser to be reflected back into the active region of the laser by the laser reflection test system as described in any one of claims 1 to 9, includes: Excitation is applied to the laser, and the reflector is coarsely adjusted by adjusting its position and angle. At the same time, the near-field image on the near-field imaging unit is observed. When a sudden change in brightness is observed in the near-field image, the reflected light has been incident near the active region of the laser. The reflector is then fixed. The reflector is finely adjusted by changing its position and angle, and the power change trend of the power meter is obtained. When the power meter reading reaches its maximum value, the reflected light is accurately incident on the active area of ​​the laser, and the position of the reflector is fixed.

14. The laser return light testing method as described in claim 13, characterized in that, The stimulus is 20%-80% of the threshold stimulus.

15. The laser return light testing method as described in claim 13, characterized in that, When the power value measured in the nth measurement is greater than the power value measured in the (n+1)th measurement, the power value measured in the nth measurement by the power meter is determined to be the maximum value.

Images