Reflection light test system and test method of laser

Abstract

The invention provides a return light testing system of a laser, which comprises a volume grating and an adjusting device, and is characterized in that return light is incident to an active area of the laser by adjusting the position and the angle of the volume grating; and increasing the light intensity of the return light until the laser fails, so as to determine the anti-return light threshold value of the laser. According to the invention, the volume grating is used to form the return light, on one hand, no interference or influence is introduced to the laser transmitted in the light path, and on the other hand, the wavelengths of the return light and the emergent light are synchronized in real time, so that the influence of the return light in the use process of the laser can be really simulated, and the return light resistance of the laser in the real use process can be measured; and the measurement precision is very high.

Description

Technical Field

[0001] The present invention relates to the field of laser technology, and in particular to a laser return light testing system and testing method. Background Art

[0002] The output wavelength of a semiconductor laser will drift with changes in 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 to the output end of the semiconductor laser, so that the wavelength of the semiconductor laser is stable and single longitudinal mode output is achieved. However, VBG wave locking is based on the Bragg reflection of light of a specific wavelength by the grating structure, forming a return light incident on the laser. The return light is absorbed by the optical film layer of the laser, which will cause the film layer temperature to increase, thereby reducing the COMD threshold of the laser front cavity film layer, causing the original design structure to fail prematurely and reducing the reliability of the laser. Therefore, it is very necessary to test the anti-return light capability of the VBG laser. Summary of the invention

[0003] The present invention provides a laser return light testing system and testing method, the specific scheme 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.

[0004] Furthermore, the return light testing system also includes a power meter; the volume grating divides the laser into two light beams, one light beam 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, and the power meter is used to test the intensity of the light beam passing through the volume grating.

[0005] Furthermore, the return light testing system also includes a wedge mirror, which is arranged on the front side of the volume grating along the laser transmission direction; along the laser transmission direction, the wedge mirror includes an incident surface and an exit surface in sequence, and the laser is refracted by the wedge mirror, emitted from the exit surface, and then enters the volume grating.

[0006] Furthermore, 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 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 enters the near-field imaging unit after being emitted through the exit surface.

[0007] Furthermore, the return light testing system also includes a spectrometer; the spectrometer is located on one side of the incident surface of the wedge-shaped mirror, and the light beam emitted by the laser is reflected by the incident surface of the wedge-shaped mirror and enters the spectrometer.

[0008] Furthermore, the return light testing system further includes a converging lens, and the converging lens is arranged at the front side of the near-field imaging unit.

[0009] In another aspect of the present application, a method for testing laser return light is provided. The method for testing laser return light is implemented based on the laser return light testing system as described above. The method for testing laser return light includes: providing a laser; 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 through the laser return light test system as described above and 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.

[0010] Furthermore, the position and angle of the volume grating are adjusted by the adjustment device so that the laser emitted by the laser forms reflected light incident on the active area of ​​the laser through the reflected light test system of the laser as described above, including: obtaining a near-field image of the laser emitted by the laser based on a near-field imaging unit, and adjusting the position and angle of the volume grating until the laser intensity on the near-field image suddenly changes; when the brightness of the laser suddenly changes, obtaining the power change amplitude of the laser based on a power meter, and obtaining the spectral range of the laser based on a spectrometer, adjusting the position and angle of the volume grating until the power change amplitude is positive and the spectral range is the narrowest, and fixing the volume grating to a target posture.

[0011] Furthermore, the incentive is 20%-80% of the threshold incentive.

[0012] Furthermore, the intensity of the reflected light is adjusted until the laser fails to determine the anti-return light threshold of the laser, including: gradually increasing the excitation, obtaining the corresponding excitation when the laser fails to determine the anti-return light threshold of the laser.

[0013] The present invention provides a laser return light testing system and testing method, which have the following technical effects: (1) The laser return light testing system and method of the present invention use a volume grating to form return light. On the one hand, the volume grating will not have any interference or influence on the light transmitted in the optical path. On the other hand, the wavelength of the return light is synchronized with the wavelength of the output light in real time. Therefore, the influence of the return light during the use of the laser can be truly simulated, and the anti-return light ability of the laser during actual use can be measured with very high measurement accuracy.

[0014] (2) The laser return light testing system and method of the present invention use a volume grating to form return light. Since the volume grating will not interfere with or affect the light transmitted in the optical path, the light intensity distribution of the return light on the front cavity surface is the same as the light intensity distribution of the outgoing light on the cavity surface. The light intensity distribution of the outgoing light can be obtained by the light intensity distribution of the return light on the front cavity surface, and the light intensity distribution of the laser front cavity surface can be further judged, such as whether there is a point with abnormal light intensity distribution. Based on this, the laser can be optimized subsequently. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments of the present invention are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0016] Figure 1 This is a structural diagram of the laser return light test system of the present invention. Figure 2 (a) is a schematic diagram of the near-field image (I). Figure 2(b) is a schematic diagram of the near-field image (II). Figure 3 This is a flow chart of the laser return light testing method. In the figure, 1. laser, 2. fast axis collimator, 3. slow axis collimator, 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 DESCRIPTION

[0017] The technical solutions in the embodiments of the present invention will be described below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0018] Embodiment 1 This embodiment provides a laser return light testing system, such as Figure 1 As shown, the transmission direction of the laser emitted by the laser 1 includes: a wedge mirror 4, a volume grating 5, and an adjustment device.

[0019] The laser light emitted by the laser 1 passes through the fast axis collimator 2 and the slow axis collimator 3 and enters the wedge mirror 4. Along the laser transmission direction, the wedge mirror 4 includes an incident surface 10 and an exit surface 11 in sequence. The light beam emitted by the laser 1 enters the wedge mirror 4 from the incident surface 10, is refracted by the wedge mirror 4, and then enters the volume grating 5 after exiting from the exit surface 11.

[0020] 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 area of ​​the laser 1 to form wavelength locking. The return light intensity is increased by adjusting the excitation of the laser 1 until the laser 1 fails, so as to determine the anti-return light threshold of the laser 1.

[0021] Further, the return light test system also includes a power meter 6, which is located behind the volume grating 5 along the laser transmission direction, and is used to measure the intensity of the laser transmitted to the power meter 6 through the volume grating 5. Further, the return light test system also includes a near-field imaging unit 9, which 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 back to the incident surface 10 by the exit surface 11 of the wedge mirror 4, and then enters the near-field imaging unit 9 after being emitted through the exit surface 11. 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.

[0022] Furthermore, the return light test system further includes a spectrometer 7, which is used to measure the spectral range of the laser light 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 light beam emitted by the laser 1 is reflected by the incident surface 12 of the wedge mirror 4 and enters the spectrometer 7.

[0023] Embodiment 2 like Figure 3 As shown, based on the return light testing system provided in the first embodiment, the return light testing method for the laser 1 includes: Applying excitation to the laser 1, adjusting the position and angle of the volume grating 5 by means of an adjusting device, so that the laser light emitted by the laser 1 forms a return light incident on the active area of ​​the laser 1, thereby forming wavelength locking; The intensity of the reflected light is adjusted until the laser 1 fails to function, so as to determine the anti-reflection light threshold of the laser 1.

[0024] Further, applying excitation to the laser 1, adjusting the position and angle of the volume grating 5 by means of an adjusting device, so that the laser light emitted by the laser 1 forms a return light incident on the active area of ​​the laser 1, including: Step (1), obtaining a near-field image of the laser light emitted by the laser 1 based on the near-field imaging unit 9, and adjusting the position and angle of the volume grating 5 by means of an adjusting device until a sudden change occurs in the brightness of the laser light on the near-field image; Specifically, the position and angle of the volume grating 5 are adjusted, and the near-field image on the near-field imaging unit 9 is obtained at the same time. When the brightness of the near-field image suddenly changes, it means that the return light has been incident near the active area of ​​the laser 1. The reason is that in addition to the electrical excitation of the laser 1 itself, the return light can be used as another optical excitation for the laser 1. When the return light is incident near the active area of ​​the laser 1 by adjusting the volume grating 5, the return light can be used as another optical excitation to act on the laser 1 itself, so that the particle beam inversion is formed in the laser 1, and the laser is emitted. Therefore, the brightness of the near-field image presented by the near-field imaging unit 9 suddenly changes, as shown in Figure 2 (b).

[0025] In order to observe a 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, no particle beam inversion is formed in the laser 1, and no laser is emitted. The near-field image presented by the near-field imaging unit 9 is shown in FIG. 2( a ).

[0026] Step (2), when the laser intensity suddenly changes, the power change amplitude of the laser is obtained based on the power meter 6, and the spectral range of the laser is obtained based on the spectrometer 7, and the position and angle of the volume grating 5 are adjusted. When the power change amplitude is positive and the spectral range is the narrowest, the return light has accurately entered the active area of ​​the laser 1. At this time, the volume grating 5 is fixed to the target posture.

[0027] It should be understood that the power variation amplitude described in the present application is positive, which means that the power of the laser obtained by the power meter 6 gradually increases when the position and angle of the volume grating 5 are adjusted. Specifically, the 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 meets the Bragg condition (that is, the wavelength matches the grating period) will be reflected back to the laser, and 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 radiation process, thereby enhancing the light output of a specific wavelength and suppressing light of other wavelengths. This feedback mechanism causes the output wavelength of the laser to be locked near the wavelength designed for the volume grating. Therefore, in this embodiment, by adjusting the position and angle of the volume grating 5, the reflected light is incident on the active area of ​​the laser, forming an optical excitation to the laser, so that the power of the beam emitted by the laser increases, so the change amplitude 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 reflected light has accurately returned to the active area, forming a wavelength lock, so at this time the output spectrum of the laser is the narrowest. In one embodiment, the excitation includes but is not limited to multiple 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.

[0028] The intensity of the returned light is adjusted until the laser 1 fails to determine the anti-return light threshold of the laser 1, including: gradually increasing the excitation of the laser 1 to obtain the excitation corresponding to the failure of the laser 1, which is the anti-return light threshold of the laser 1.

[0029] Based on the return light testing system and method provided in this embodiment, the return light is formed with the help of the volume grating 5. On the one hand, the volume grating 5 will not have any interference or influence on the laser transmitted in the optical path. On the other hand, the wavelength of the return light is synchronized with the wavelength of the output light in real time. Therefore, the influence of the return light during the use of the laser 1 can be truly simulated, and the anti-return light ability of the laser 1 during actual use can be measured, and the measurement accuracy is very high.

[0030] On the other hand, the present embodiment forms the return light with the help of the volume grating 5. Since the volume grating 5 will not have any interference or influence on the laser transmitted in the optical path, the intensity distribution of the outgoing light on the front cavity surface of the laser 1 can be simulated by measuring the intensity distribution of the return light on the front cavity surface. The intensity distribution of the outgoing light can be obtained by measuring the intensity distribution of the return light on the front cavity surface, and the intensity distribution of the front cavity surface of the laser 1 can be further judged, for example, whether there is a point with abnormal intensity distribution, and based on this, the laser 1 can be optimized later.

[0031] 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 it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the 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: providing a laser; Applying excitation to the laser, adjusting the position and angle of the volume grating by means of an adjustment 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; The intensity of the reflected light is adjusted 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 adjusting device is used to adjust the position and angle of the volume grating so that the laser emitted by the laser forms reflected light incident on the active area of ​​the laser through the reflected light testing system of the laser according to any one of claims 1 to 6, comprising: 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 intensity of the returned light is adjusted until the laser fails to determine the anti-return light threshold of the laser, including: gradually increasing the excitation, obtaining the corresponding excitation when the laser fails to determine the anti-return light threshold of the laser.

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