Return light test system and test method for a laser

Abstract

The present invention provides a return light test system for a laser, comprising: a volume grating and an adjusting device. By adjusting the position and angle of the volume grating, the return light is made to be incident on the active region of the laser; the light intensity of the return light is increased until the laser fails, so as to determine the return light resistance threshold of the laser. By using the volume grating to form the return light, on the one hand, no interference or influence is introduced to the laser transmitted in the optical path, and on the other hand, the wavelength of the return light is synchronized with the emitted light in real time. Therefore, the influence of the return light during the use of the laser can be truly simulated, and the return light resistance ability of the laser during actual use can be measured, and the measurement accuracy is very high.

Description

Technical Field

[0001] The present invention relates to the field of laser technology, and more particularly, to a return light test system and a test method for a laser. Background Art

[0002] The output wavelength of a semiconductor laser will drift with the change of temperature or current, which will have a serious impact on the performance of the semiconductor laser. To solve this problem, a common method is to add a volume Bragg grating (VBG) external cavity structure at the output end of the semiconductor laser, so that the wavelength of the semiconductor laser is stabilized and single longitudinal mode output is achieved. However, VBG wavelength locking is based on the Bragg reflection of light with a specific wavelength by the grating structure, forming return light incident on the laser. The absorption of the return light by the optical film layer of the laser will cause the temperature of the film layer to increase, thereby reducing the COMD threshold of the front cavity film layer of the laser, resulting in premature failure of the original design structure and reducing the reliability of the laser. Therefore, it is very necessary to test the anti-return light ability of VBG lasers. Summary of the Invention

[0003] The present invention provides a return light test system and a test method for a laser. The specific scheme includes a volume grating and an adjustment device;

[0004] The volume grating is arranged on the propagation path of the laser emitted by the laser, and is used for reflecting the laser to form return light;

[0005] The adjustment device is used for adjusting the position and angle of the volume grating, so that the return light is incident on the active region of the laser;

[0006] Adjust the light intensity of the return light until the laser fails, so as to determine the anti-return light threshold of the laser.

[0007] Furthermore, the return light test system further includes a power meter; the volume grating divides the laser into two partial light beams, one partial light beam is reflected by the volume grating to form the return light, and the other partial light beam passes through the volume grating and is incident on the power meter, and the power meter is used for testing the light intensity of the light beam passing through the volume grating.

[0008] Furthermore, the return light test system further includes a wedge mirror, and the wedge mirror is arranged on the front side of the volume grating along the laser transmission direction; along the laser transmission direction, the wedge mirror sequentially includes an incident surface and an exit surface, and the laser is refracted by the wedge mirror and exits from the exit surface and then enters the volume grating.

[0009] Further, the return light test system further includes a near-field imaging unit, which is located on the side of 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 and enters the near-field imaging unit.

[0010] Further, the return light test system further includes a spectrometer; the spectrometer is located on one side of the incident surface of the wedge mirror, and the beam emitted by the laser is reflected by the incident surface of the wedge mirror and enters the spectrometer.

[0011] Further, the return light test system further includes a converging lens, and the converging lens is arranged on the front side of the near-field imaging unit.

[0012] On the other hand, the present application provides a method for testing the return light of a laser. The method for testing the return light of the laser is implemented based on the above-mentioned return light test system of the laser, and the return light test method includes:

[0013] Providing a laser;

[0014] Applying an excitation to the laser, and adjusting the position and angle of the volume grating through the adjusting device of the return light test system of the laser, so that the laser emitted by the laser forms a return light through the return light test system of the laser as described above and is incident on the active region of the laser;

[0015] Adjusting the light intensity of the return light until the laser fails to determine the return light resistance threshold of the laser.

[0016] Further, adjusting the position and angle of the volume grating through the adjusting device, so that the laser emitted by the laser forms a return light through the return light test system of the laser as described above and is incident on the active region of the laser, includes: obtaining a near-field image of the laser emitted by the laser based on the near-field imaging unit, and adjusting the position and angle of the volume grating until a sudden change in the laser intensity occurs on the near-field image; when a sudden change in the brightness of the laser occurs, obtaining the amplitude of the power change of the laser based on a power meter, and obtaining the spectral range of the laser based on a spectrometer, and adjusting the position and angle of the volume grating until the amplitude of the power change is positive and the spectral range is the narrowest, and fixing the volume grating to the target posture.

[0017] Further, the excitation is 20%-80% of the threshold excitation.

[0018] Further, adjusting the light intensity of the return light until the laser fails to determine the return light resistance threshold of the laser, includes: gradually increasing the excitation, and obtaining the excitation corresponding to when the laser fails to determine the return light resistance threshold of the laser.

[0019] The present invention provides a system and method for testing the retroreflected light of a laser, which have the following technical effects:

[0020] (1) For the system and method for testing the retroreflected light of the laser of the present invention, the retroreflected light is formed by means of a volume grating. On the one hand, the volume grating will not cause any interference or influence on the light transmitted in the optical path. On the other hand, the wavelength of the retroreflected light is synchronized with the wavelength of the emitted light in real time. Therefore, the influence of the retroreflected light during the use of the laser can be truly simulated, and the anti-retroreflected light ability of the laser during actual use can be measured, and the measurement accuracy is very high.

[0021] (2) For the system and method for testing the retroreflected light of the laser of the present invention, the retroreflected light is formed by means of a volume grating. Since the volume grating will not cause any interference or influence on the light transmitted in the optical path, the light intensity distribution of the retroreflected light on the front cavity surface is the same as the light intensity distribution of the emitted light on the cavity surface. The light intensity distribution of the emitted light can be obtained from the light intensity distribution of the retroreflected light on the front cavity surface, and further judge the light intensity distribution of the front cavity surface of the laser, such as whether there are points with abnormal light intensity distribution. Based on this, the laser can be optimized subsequently. Description of the Drawings

[0022] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required for use in the embodiments of the present invention. It should be understood that the following drawings only show some embodiments of the present invention, and therefore should not be regarded as limiting the scope. For those of ordinary skill in the art, other related drawings can be obtained based on these drawings without creative efforts.

[0023] Figure 1 It is a structural diagram of the system for testing the retroreflected light of the laser of the present invention.

[0024] Figure 2(a) is a schematic diagram of the near-field image (I).

[0025] Figure 2(b) is a schematic diagram of the near-field image (II).

[0026] Figure 3 It is a flowchart of the method for testing the retroreflected light of the laser.

[0027] In the figure, 1. Laser, 2. Fast-axis collimating mirror, 3. Slow-axis collimating mirror, 4. Wedge mirror, 5. Volume grating, 6. Power meter, 7. Spectrometer, 8. Converging lens, 9. Near-field imaging unit, 10. Incident surface, 11. Exit surface. Detailed Embodiments

[0028] The following will describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention.

[0029] Embodiment 1

[0030] This embodiment provides a return light test system for a laser, as Figure 1 shown, along the laser transmission direction emitted by the laser 1, it successively includes: a wedge mirror 4, a volume grating 5, and an adjustment device.

[0031] The laser emitted by the laser 1 passes through the fast axis collimating mirror 2 and the slow axis collimating mirror 3 and is incident on the wedge mirror 4. Along the laser transmission direction, the wedge mirror 4 successively includes an incident surface 10 and an exit surface 11. The beam emitted by the laser 1 enters the wedge mirror 4 from the incident surface 10, and after being refracted by the wedge mirror 4, it exits from the exit surface 11 and then enters the volume grating 5.

[0032] The volume grating 5 is used to reflect the laser to form return light, and the adjustment device is used to adjust the position and angle of the volume grating 5 so that the return light is incident on the active region of the laser 1 to form wavelength locking. By adjusting the excitation of the laser 1 to increase the return light intensity until the laser 1 fails, the return light resistance threshold of the laser 1 is determined.

[0033] Further, the return light test system further includes a power meter 6, which is located behind the volume grating 5 along the laser transmission direction and is used to measure the laser intensity transmitted through the volume grating 5 to the power meter 6. Further, the return light test system further includes a near-field imaging unit 9. The near-field imaging unit 9 is used to determine the near-field image of the laser emitted by the laser 1. The near-field imaging unit 9 is located on one side of the exit surface 11 of the wedge mirror 4. The laser passes through the wedge mirror 4, is reflected by the exit surface 11 of the wedge mirror 4 back to the incident surface 10, and then exits through the exit surface 11 and enters the near-field imaging unit 9. A converging lens 8 can be added before the near-field imaging unit 9 to image the near-field image of the laser to the near-field imaging unit 9.

[0034] Further, the return light test system further includes a spectrometer 7. The spectrometer 7 is used to measure the spectral range of the laser emitted by the laser 1. The spectrometer 7 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 and enters the spectrometer 7.

[0035] Embodiment Two

[0036] As Figure 3 shown, based on the return light test system provided in Embodiment One, the method for testing the return light of the laser 1 includes:

[0037] Apply excitation to the laser 1, and adjust the position and angle of the volume grating 5 through the adjustment device so that the laser emitted by the laser 1 forms return light and is incident on the active region of the laser 1 to form wavelength locking;

[0038] Adjust the intensity of the return light until the laser 1 fails to determine the return light resistance threshold of the laser 1.

[0039] Further, an excitation is applied to the laser 1, and the position and angle of the volume grating 5 are adjusted by an adjusting device so that the laser emitted by the laser 1 forms retroreflected light that is incident on the active region of the laser 1, including:

[0040] Step (1): Based on the near-field imaging unit 9, obtain the near-field image of the laser emitted by the laser 1, and adjust the position and angle of the volume grating 5 by the adjusting device until a sudden change in the laser brightness occurs in the near-field image;

[0041] Specifically, adjust the position and angle of the volume grating 5, and at the same time obtain the near-field image on the near-field imaging unit 9. When a sudden change in brightness occurs in the near-field image, it indicates that the retroreflected light has been incident near the active region of the laser 1. The reason is that in addition to the electrical excitation of the laser 1 itself, the retroreflected light can serve as another optical excitation for the laser 1. When the retroreflected light has been incident near the active region of the laser 1 by adjusting the volume grating 5, the retroreflected light can then act as another optical excitation on the laser 1 itself, causing population inversion to form in the laser 1 and laser to be emitted. Therefore, a sudden change in brightness occurs in the near-field image presented by the near-field imaging unit 9, as shown in Fig. 2(b).

[0042] To observe the sudden change in brightness of the near-field image in step (1), the electrical excitation of the laser 1 is 20% - 80% of the threshold excitation. That is, in the case of only electrical excitation, population inversion does not form in the laser 1 and no laser is emitted, and the near-field image presented by the near-field imaging unit 9 is as shown in Fig. 2(a).

[0043] Step (2): When a sudden change in laser intensity occurs, obtain the amplitude of the power change of the laser based on the power meter 6, and obtain the spectral range of the laser based on the spectrometer 7. Adjust the position and angle of the volume grating 5. When the amplitude of the power change is positive and the spectral range is the narrowest, the retroreflected light has been accurately incident on the active region of the laser 1, and at this time, fix the volume grating 5 to the target attitude.

[0044] It should be understood that when the amplitude of the power change described in this application is positive, it means that the power of the laser obtained by the power meter 6 gradually increases when adjusting the position and angle of the volume grating 5. Specifically, a volume grating is a volume grating with periodic refractive index modulation, which can produce Bragg reflection for light of a specific wavelength. When the light output by the laser passes through the volume grating, only the light that satisfies the Bragg condition (i.e., the wavelength matches the grating period) will be reflected back to the laser, and the light of other wavelengths will be transmitted or scattered. The light reflected back to the laser re-enters the active region and participates in the stimulated emission process, thereby enhancing the output of light of a specific wavelength and suppressing the light of other wavelengths. This feedback mechanism locks the output wavelength of the laser near the wavelength designed by the volume grating. Therefore, in this embodiment, by adjusting the position and angle of the volume grating 5, the return light is incident on the active region of the laser, forming an optical excitation of the laser, so that the power of the laser beam emitted increases. Therefore, the amplitude of the change of the power meter 6 is positive, and when the position and angle of the volume grating are adjusted to make the laser spectrum range obtained by the spectrometer 7 the narrowest, it means that the return light has accurately returned to the active region, forming wavelength locking. Therefore, the output spectrum of the laser is the narrowest at this time. In one of the implementation manners, the excitation includes but is not limited to various excitation methods such as optical excitation, electrical excitation, and chemical excitation. In this application, the excitation method of the laser is electrical excitation, and the threshold excitation is the electrical excitation threshold.

[0045] Adjust the light intensity of the return light until the laser 1 fails to determine the return light resistance threshold of the laser 1, including: gradually increasing the excitation of the laser 1 and obtaining the corresponding excitation when the laser 1 fails, which is the return light resistance threshold of the laser 1.

[0046] Based on the return light test system and method provided in this embodiment, by forming return light with the help of the volume grating 5, on the one hand, the volume grating 5 will not cause any interference or influence on the laser transmitted in the optical path, and on the other hand, the return light is synchronized with the wavelength of the outgoing light in real time. Therefore, the influence of the return light during the use of the laser 1 can be truly simulated, and the return light resistance ability of the laser 1 during actual use can be measured, and the measurement accuracy is very high.

[0047] On the other hand, this embodiment forms return light with the help of the volume grating 5. Since the volume grating 5 will not cause any interference or influence on the laser transmitted in the optical path, the light intensity distribution of the outgoing light on the front cavity surface of the laser 1 can be simulated by measuring the light intensity distribution of the return light on the front cavity surface of the laser 1. The light intensity distribution of the outgoing light can be obtained by measuring the light intensity distribution of the return light on the front cavity surface, and further judge the light intensity distribution of the front cavity surface of the laser 1, such as whether there are points with abnormal light intensity distribution, and based on this, the laser 1 can be optimized subsequently.

[0048] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A laser return light testing system, characterized in that: It includes a volume grating and an adjustment device; The volume grating is arranged in the propagation path of the laser light emitted by the laser device, and is used to reflect the laser light to form return light; The adjusting device is used to adjust the position and angle of the volume grating so that the reflected light is incident on the active area of ​​the laser; The intensity of the reflected light is adjusted until the laser fails, so as to determine the anti-reflection light threshold of the laser.

2. A laser return light testing system as claimed in claim 1, characterized in that: The return light testing system also includes a power meter; the volume grating divides the laser into two light beams, one of which is reflected by the volume grating to form the return light, and the other light beam passes through the volume grating and is incident on the power meter. The power meter is used to test the light intensity of the light beam passing through the volume grating.

3. The laser return light testing system according to claim 1, characterized in that: The return light testing system further comprises a wedge mirror, which is arranged at the front side of the volume grating along the laser transmission direction; Along the laser transmission direction, the wedge-shaped mirror includes an incident surface and an exit surface in sequence. The laser is refracted by the wedge-shaped mirror, exits from the exit surface, and then enters the volume grating.

4. A laser return light testing system as claimed in claim 3, characterized in that: The return light testing system also includes a near-field imaging unit, which is located on one side of the exit surface of the wedge-shaped mirror. The laser passes through the wedge-shaped mirror, is reflected back to the incident surface by the exit surface of the wedge-shaped mirror, and then enters the near-field imaging unit after being emitted through the exit surface.

5. The laser return light testing system as claimed in claim 3, characterized in that: The back-return light testing system further comprises a spectrometer; the spectrometer is located on one side of the incident surface of the wedge-shaped mirror, and the laser light emitted by the laser is reflected by the incident surface of the wedge-shaped mirror and enters the spectrometer.

6. The laser return light testing system according to claim 4, characterized in that: The back-reflection light testing system further includes a converging lens, which is disposed at the front side of the near-field imaging unit.

7. A method for testing the return light of a laser, characterized in that: The return light test method is implemented based on the return light test system of the laser according to any one of claims 1 to 6, and the method comprises: Step S1, providing a laser; Step S2, applying excitation to the laser, adjusting the position and angle of the volume grating by means of an adjusting device of the laser return light test system, so that the laser emitted by the laser forms return light incident on the active area of ​​the laser through the laser return light test system according to any one of claims 1 to 6; Step S3, adjusting the intensity of the reflected light until the laser fails, so as to determine the anti-reflection light threshold of the laser.

8. A laser return light testing method as claimed in claim 7, characterized in that: The step S2 comprises: Acquire a near-field image of the laser light emitted by the laser based on a near-field imaging unit, and adjust the position and angle of the volume grating until a sudden change occurs in the laser intensity on the near-field image; When the brightness of the laser changes suddenly, the power change amplitude of the laser is obtained based on the power meter, and the spectral range of the laser is obtained based on the spectrometer, and the position and angle of the volume grating are adjusted until the power change amplitude is positive and the spectral range is narrowest, and the volume grating is fixed to the target posture.

9. A laser return light testing method as claimed in claim 7, characterized in that: The incentive is 20%-80% of the threshold incentive.

10. A laser return light testing method as claimed in claim 7, characterized in that: The step S3 includes: gradually increasing the excitation, obtaining the excitation corresponding to the laser failure, and determining the anti-return light threshold of the laser.

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