Reflection light test system and test method of laser

Abstract

The invention provides a system and a method for testing return light of a laser, the system for testing the return light comprises a return light energy adjusting unit and a reflector in sequence along the transmission direction of laser emitted by the laser, and the light intensity of the return light is adjusted until the laser fails so as to determine the return light resistance threshold value of the laser. The reflecting mirror is used for forming 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 wavelength of the return light and the wavelength of 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 technical field of semiconductor lasers, and in particular to a laser return light testing system and testing method. Background Art

[0002] The front cavity surface of the laser is coated with an optical film. Due to the reversibility of the optical path, part of the light beam will be reflected back to the front cavity surface of the laser when there is no isolator or other device in the optical path. The optical film is extremely sensitive to temperature. The absorption of the reflected light by the optical film will cause the film temperature to increase, thereby reducing the COMD threshold of the laser front cavity surface film, causing the original design structure to fail prematurely and reducing the reliability of the laser. Therefore, it is very necessary to test the laser's ability to resist reflected light.

[0003] Common laser return light capability test systems include the following two types: (1) Use optical fiber structure to build the return light path, and the laser emitted by the light source is returned to the light output cavity surface through the optical fiber. The output laser from the front cavity surface of the laser has edge loss when coupled into the optical fiber, and the beam is shaped and rotated during transmission in the optical fiber, and the optical fiber is bent, which will cause abnormal return light. Therefore, when building the return light through optical fiber, due to the above-mentioned influence of the optical fiber itself on the return light during optical fiber transmission, it is impossible to faithfully simulate the effect of the return light on the chip cavity surface during the actual use of the laser, resulting in insufficient measurement accuracy.

[0004] On the other hand, the power that optical fiber can carry is relatively low. For lasers with relatively large output light power, such as around 100W, the power range of the optical fiber that can carry the transmission light beam is exceeded, and optical fiber cannot be used for coupled transmission and measurement of anti-return light capability.

[0005] (2) Introducing external light as a light source to simulate the return light. Since the optical film layer is sensitive to the wavelength of light, and each laser has some random wavelength drift due to its own heat dissipation during operation, even if a laser with the same wavelength is introduced as external light, it is impossible to simulate and reproduce the wavelength of the laser being tested in real time due to the difference in heat dissipation and temperature drift during operation. Therefore, the introduction of an external laser cannot simulate the real-time impact of the return light on the laser being tested during actual use.

[0006] Therefore, the prior art cannot truly simulate the reflected light received by the laser during use, and thus cannot accurately measure the anti-reflection light capability of the laser during use. Summary of the invention

[0007] The present invention provides a return light test system and a test method for a laser. The return light test system along the transmission direction of the laser emitted by the laser sequentially comprises: a return light energy adjustment unit and a reflector; The reflector is arranged in the propagation path of the laser, and is used to reflect the laser to form return light, and make the return light incident on the active area of ​​the laser; The return light energy adjustment unit is arranged in the propagation path of the return light, and is used to adjust the light intensity of the return light until the laser fails, so as to determine the anti-return light threshold of the laser.

[0008] Furthermore, the return light energy adjustment unit comprises a half-wave plate and a polarization beam splitter prism sequentially arranged along the laser transmission direction, and the polarization beam splitter prism adjusts the intensity of the return light by adjusting the rotation angle of the half-wave plate.

[0009] Furthermore, the return light energy adjustment unit also includes a power meter, and the polarization beam splitter prism splits the return light into two light beams, one light beam passes through the polarization beam splitter prism and is incident on the active area of ​​the laser, and the other light beam is reflected by the polarization beam splitter prism and enters the power meter.

[0010] Furthermore, the return light testing system also includes a wedge mirror, which is arranged in front of the return light 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, and the light beam emitted by the laser is refracted by the wedge mirror, and enters the return light energy adjustment unit after being emitted from the exit surface.

[0011] 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.

[0012] 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.

[0013] Furthermore, the return light testing system also includes an adjustment device for adjusting the position and angle of the reflector until the return light is reflected by the reflector and then incident on the active area of ​​the laser via the return light energy adjustment unit.

[0014] Another aspect of the present application further provides a method for testing the return light of a laser, the method comprising: providing a laser; Applying excitation to the laser, so that the laser emitted by the laser passes through the laser return light testing system as described above to form return light incident on the active area of ​​the laser; The light intensity of the returned light is adjusted by a returned light energy adjustment unit until the laser fails, so as to determine the anti-return light threshold of the laser.

[0015] Furthermore, the intensity of the returned light is adjusted by a returned light energy adjustment unit until the laser fails to determine the anti-return light threshold of the laser, including: rotating the half-wave plate of the return light test system of the laser to a preset rotation angle, gradually increasing the excitation of the laser until the laser fails, and 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 rotation angle of the half-wave plate and the excitation.

[0016] Furthermore, if the laser does not fail 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 returned light until the laser fails; and the anti-return light threshold of the laser is determined based on the rotation angle of the half-wave plate and the excitation.

[0017] Furthermore, applying excitation to the laser so that the laser emitted by the laser forms reflected light incident on the active area of ​​the laser through the laser reflected light test system as described above, including: applying excitation to the laser, roughly adjusting the reflector, adjusting the position and angle of the reflector, and observing the near-field image on the near-field imaging unit at the same time. When a sudden change in brightness of the near-field image is observed, the reflected light has been incident on the vicinity of the active area of ​​the laser, and the reflector is fixed; finely adjusting the reflector, adjusting the position and angle of the reflector, and obtaining the power change trend of the power meter. When the power meter reading reaches the maximum value, the reflected light is accurately incident on the active area of ​​the laser, and the position of the reflector is fixed.

[0018] Furthermore, the incentive is 20%-80% of the threshold incentive.

[0019] The present invention provides a laser return light testing system and testing method, which have the following technical effects: (1) The laser return light test system and test method of the present invention use a reflector to form return light. On the one hand, the reflector 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 can be truly simulated, and the anti-return light ability of the laser during actual use can be measured. The measurement accuracy is very high.

[0020] (2) The return light testing system and method of the laser of the present invention uses a reflector to form the return light. Since the reflector will not interfere with or affect the laser 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 semiconductor front cavity surface can be further judged, such as whether there is a point of abnormal light intensity distribution. Based on this, the laser can be optimized subsequently. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] 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.

[0022] 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 graph showing the relationship between the rotation angle of the half-wave plate and the proportion of the reflected light relative to the laser light intensity emitted by the laser. Figure 4 is a schematic flow chart of a laser return light testing method of the present invention, In the figure, 1. laser, 2. fast axis collimator, 3. slow axis collimator, 4. wedge mirror, 5. half-wave plate, 6. polarization beam splitter, 7. reflector, 8. power meter, 9. spectrometer, 10. converging lens, 11. near-field imaging unit, 12. incident surface, 13. exit surface. DETAILED DESCRIPTION

[0023] 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.

[0024] Embodiment 1 This embodiment provides a laser return light testing system, such as Figure 1 As shown, the laser transmission direction emitted by the laser 1 includes: a wedge mirror 4, a return light energy adjustment unit and a reflector 7, and an adjustment device.

[0025] 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 12 and an exit surface 13 in sequence. The light beam emitted by the laser 1 enters the wedge mirror 4 from the incident surface 12, is refracted by the wedge mirror 4, and then exits from the exit surface 13 and enters the return light energy adjustment unit.

[0026] The reflector 7 is used to reflect the laser to form a return light, and the adjustment device is used to adjust the position and angle of the reflector 7 so that the return light is reflected by the reflector 7 to the active area of ​​the laser 1. The return light energy adjustment unit is used to adjust the intensity of the return light until the laser 1 fails, so as to determine the anti-return light threshold of the laser 1.

[0027] The return light energy adjustment unit includes a half-wave plate 5 and a polarization beam splitter prism 6 which are sequentially arranged along the laser transmission direction. The polarization beam splitter prism 6 adjusts the intensity of the return light by adjusting the rotation angle of the half-wave plate 5. Further, the return light energy adjustment unit also includes a power meter 8. The polarization beam splitter prism 6 splits the return light into two light beams. One part of the light beam is incident on the active area of ​​the laser 1 through the polarization beam splitter prism 6, and the other part of the light beam is reflected by the polarization beam splitter prism 6 and enters the power meter 8. The power meter 8 is used to measure the intensity of the light beam reflected by the polarization beam splitter prism 6.

[0028] Furthermore, the return light test system further includes a near-field imaging unit 11, which is used to determine the near-field image of the laser light emitted by 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 light 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 enters the near-field imaging unit 11 after being emitted through the exit surface 13. A converging lens 10 may be added before the near-field imaging unit 11, so that the near-field image of the laser light is imaged on the near-field imaging unit 11 after passing through the converging lens 10.

[0029] Furthermore, the back-reflection light test system further includes a spectrometer 9, which is used to determine the wavelength of the laser emitted by the laser 1, so as to determine the anti-back-reflection light 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-shaped mirror 4, and the light beam emitted by the laser 1 is reflected by the incident surface 12 of the wedge-shaped mirror 4 and enters the spectrometer 9.

[0030] Embodiment 2 like Figure 4 As shown, based on the return light testing system provided in the first embodiment of the present application, the return light testing method for the laser 1 includes: Applying excitation to the laser 1, so that the laser emitted by the laser 1 forms a reflected light through the reflected light test system and is incident on the active area of ​​the laser 1; 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 .

[0031] Further, applying excitation to the laser 1 so that the laser emitted by the laser 1 forms reflected light through the reflected light testing system and is incident on the active area of ​​the laser 1 includes the following two steps: Step (1), applying excitation to the laser 1, and roughly adjusting the reflector 7 so that the reflected light is incident near the active area of ​​the laser 1, as shown in FIG2(a).

[0032] Specifically, the position and angle of the reflector 7 are adjusted, and the near-field image on the near-field imaging unit 11 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 reflector 7, the return light can be used as another optical excitation to act on the laser 1 itself, so that the particle beam formed in the laser 1 is reversed and the laser is emitted. Therefore, a sudden change in brightness can be observed from the near-field image formed by the near-field imaging unit 11, as shown in the change from Figure 2 (a) to Figure 2 (b).

[0033] In order to observe a sudden change in brightness 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, in the case of only electrical excitation, no particle beam inversion is formed in the laser 1, and spontaneous fluorescence is generated instead of emitting laser light. The near-field image formed by the near-field imaging unit 11 is shown in FIG. 2( a ).

[0034] Step (2), fine-tuning the reflector 7 so that the reflected light is accurately incident on the active area of ​​the laser 1.

[0035] 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 the maximum value, it means that the reflected light has accurately entered the active area 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 reaches the maximum value, so the laser intensity emitted by the laser 1 reaches the 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.

[0036] Among them, the method for determining whether the indication of the power meter 8 has reached the maximum value may include but is not limited to determining the maximum value based on the power value measured by the power meter 8 for the nth time, the power value measured for the n-1th time, and the power value measured for the n+1th time; in the process of adjusting the position and angle of the reflector 7, always ensure that the power value measured for the nth time is greater than the power value measured for the n-1th time. When the power value measured for the nth time is greater than the power value measured for the n+1th time, it is determined that the power value measured for the nth time by the power meter 8 is the maximum value.

[0037] Further, 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, including: 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-return light threshold of the laser 1 based on the rotation angle of the half-wave plate 5 and the electrical excitation of the laser 1.

[0038] If the laser 1 does not fail even when the electrical excitation increases to the maximum value, the rotation angle of the half-wave plate 5 is adjusted to increase the intensity of the returned light until the laser 1 fails. The relationship between the rotation angle of the half-wave plate 5 and the light feedback intensity curve of the returned light is as follows: Figure 3 As shown; the anti-return light 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.

[0039] Specifically, the greater the excitation applied to the laser, the higher the power of the laser light emitted by the laser (that is, the higher the power of the returned light). By adjusting the rotation angle of the half-wave plate 5, the intensity of the light beam returned to the active area of ​​the laser 1 can be adjusted, that is, by adjusting the half-wave plate 5, a certain proportion of the intensity of the laser light emitted by the laser 1 can be returned to the active area of ​​the laser 1. Figure 3 It is a relationship diagram of the rotation angle of the half-wave plate 5 and the proportion of the reflected light relative to the laser light intensity emitted by the laser 1; further, the anti-return light threshold of the laser 1 can be determined according to the proportion and the light intensity of the laser emitted by the laser 1.

[0040] Specifically, the principle of adjusting the energy of the returning light by the half-wave plate 5 and the polarization beam splitter prism 6 in this embodiment is as follows: the half-wave plate 5 has two main axes, namely the fast axis and the slow axis, and the refractive indexes on the two axes are different, so the light speed is also different. 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 main axis of the wave plate. When the polarization direction of the incident light coincides with the fast axis or the slow axis, the polarization direction remains unchanged. The half-wave plate 5 can continuously adjust the polarization direction. Assuming that the angle between the polarization direction and the slow axis is θ, after the light beam passes through the half-wave plate 5, the light phase of the fast axis is added with π, and the angle of rotation of the polarization direction is 2θ.

[0041] The polarization beam splitter prism 6 is an optical element that splits an incident light beam into two beams of light whose propagation directions are perpendicular to each other. However, unlike a general optical beam splitter element, there is a special relationship between the two beams of light separated by it, that is, both beams of light are linearly polarized light, and the polarization directions are perpendicular to each other. In this embodiment, the intensity of the returning light is mainly determined by the returning light energy adjustment unit composed of the half-wave plate 5 and the polarization beam splitter prism 6, and the intensity of the returning 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, and the polarization beam splitter prism 6 can make P light (parallel polarized light, i.e., light whose electric field vibration direction is parallel to the incident plane, and the incident plane refers to the plane formed by the incident light and the normal line, and for P light, its electric vector is located in the incident plane) pass through, and S light (vertically 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) reflect, and the combination of the two can realize the continuous adjustment of the returning light energy.

[0042] Based on the return light testing system and method provided in this embodiment, the return light is formed by using the reflector 7. On the one hand, the reflector 7 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.

[0043] On the other hand, the present embodiment uses the reflector 7 to form the returned light. Since the reflector 7 does not interfere with or affect the laser transmitted in the optical path, the intensity distribution of the emitted light on the front cavity surface of the laser 1 can be simulated by measuring the intensity distribution of the returned light on the front cavity surface. The intensity distribution of the emitted light can be obtained by measuring the intensity distribution of the returned 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 subsequently.

[0044] 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: The laser transmission direction along the laser output of the laser includes: a return light energy adjustment unit and a reflector; The reflector is arranged in the propagation path of the laser, and is used to reflect the laser to form return light, and make the return light incident on the active area of ​​the laser; The return light energy adjustment unit is arranged in the propagation path of the return light, and is used to adjust the light intensity of the return light until the laser fails, so as to determine the anti-return light threshold of the laser.

2. A laser return light testing system as claimed in claim 1, characterized in that: The return light energy adjustment unit comprises a half-wave plate and a polarization beam splitter prism which are sequentially arranged along the laser transmission direction. The polarization beam splitter prism adjusts the intensity of the return light by adjusting the rotation angle of the half-wave plate.

3. A laser return light testing system as claimed in claim 2, characterized in that: The return light energy adjustment unit also includes a power meter. The polarization beam splitter prism splits the return light into two light beams. One light beam passes through the polarization beam splitter prism and enters the active area of ​​the laser. The other light beam is reflected by the polarization beam splitter prism and enters the power meter.

4. 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 in front of the return light energy adjustment unit 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 light beam emitted by the laser is refracted by the wedge-shaped mirror, and enters the return light energy adjustment unit after being emitted from the exit surface.

5. A laser return light testing system as claimed in claim 4, 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.

6. A laser return light testing system as claimed in claim 4, characterized in that: The 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 light beam emitted by the laser is reflected by the incident surface of the wedge-shaped mirror and enters the spectrometer.

7. The laser return light testing system according to claim 1, characterized in that: The return light testing system also includes an adjusting device for adjusting the position and angle of the reflector until the return light is reflected by the reflector and incident on the active area of ​​the laser through the return light energy adjusting unit.

8. A method for testing the return light of a laser, characterized in that: The back-return light testing method comprises: providing a laser; Applying excitation to the laser so that the laser emitted by the laser forms reflected light incident on the active area of ​​the laser through the laser reflected light testing system according to any one of claims 1 to 7; The light intensity of the returned light is adjusted by a returned light energy adjustment unit until the laser fails, so as to determine the anti-return light threshold of the laser.

9. A laser return light testing method as claimed in claim 8, characterized in that: The light intensity of the returned light is adjusted by a returned light energy adjustment unit until the laser fails, so as to determine the anti-return light threshold of the laser, including: Rotate the half-wave plate of the laser return light 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-return light threshold of the laser based on the rotation angle of the half-wave plate and the excitation.

10. A laser return light testing method as claimed in claim 9, characterized in that: If the laser does not fail 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 returned light until the laser fails; the anti-return light threshold of the laser is determined based on the rotation angle of the half-wave plate and the excitation.

11. A laser return light testing method as claimed in claim 8, characterized in that: Applying excitation to the laser 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 for the laser according to any one of claims 1 to 7, comprising: Applying excitation to the laser, roughly adjusting the reflector, adjusting the position and angle of the reflector, and observing the near-field image on the near-field imaging unit at the same time. When a sudden change in brightness of the near-field image is observed, the return light has been incident near the active area of ​​the laser, and the reflector is fixed; Fine-tune the reflector, adjust its position and angle, and obtain the power change trend of the power meter. When the power meter reading reaches the maximum value, the return light accurately enters the active area of ​​the laser, and the position of the reflector is fixed.

12. A laser return light testing method as claimed in claim 11, characterized in that: The incentive is 20%-80% of the threshold incentive.

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