External cavity tunable laser linewidth compression system for realizing wavelength phase locking based on mutual injection of gain chips

Abstract

The invention discloses an external cavity tunable laser linewidth compression system for realizing wavelength phase locking based on mutual injection of gain chips. The external cavity tunable laser linewidth compression system comprises a red light semiconductor laser main gain chip, a first collimation optical system, a blazed grating, a tuning rotating mirror, a reflector, a power supply driving system and a double-path feedback amplification system, the double-path feedback amplification system comprises a first secondary gain chip, a second secondary gain chip, a second collimation optical system, a third collimation optical system and a polarization-free beam splitter prism; and the red light semiconductor laser main gain chip, the first secondary gain chip and the second secondary gain chip are all connected with the power supply driving system. Therefore, the technical problems of low output infrared light power, poor stability and narrow mode-hopping-free tuning range in the prior art are solved, and high-power, narrow-linewidth, high-stability and large-range mode-hopping-free continuous tuning red light output can be realized.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of red light semiconductor laser, more particularly, to a high-power Littman linewidth compression structure based on mutual injection of multiple gain chips to realize wavelength phase locking. BACKGROUND

[0002] The rapid development of integrated circuit manufacturing technology puts forward higher requirements for raw materials and process accuracy. The integrated production line generally adopts a semiconductor laser coherent detection method to confirm the material surface processing quality. In order to improve the detection accuracy, the spectral performance of the semiconductor laser needs to be improved, including compressing the linewidth of the laser, improving the wavelength tuning stability, etc. One of the main methods to achieve linewidth compression and wavelength tuning is to build a grating external cavity, among which the commonly selected designs are Littrow and Littman external cavity structures.

[0003] The basic principle of Littrow and Littman external cavity is that the light emitted by the laser is collimated and then incident on the blazed grating. The 1st order diffraction light of a specific wavelength is fed back to the active region of the laser, and this wavelength is amplified in the active region to become the main mode, while the lasing of other wavelengths is suppressed, and finally output through the 0th order diffraction of the grating. The difference between the two structures is that the Littrow structure relies on the 1st order diffraction of the grating to form feedback, and the tuning is completed by rotating the grating, and the output direction will change with the rotation of the grating. The Littman structure uses a plane mirror to feed back the 1st order light through the grating twice, and the tuning is completed by rotating the plane mirror, which has the advantages of narrower linewidth and unchanged output laser direction, and is widely used in coherent detection light sources.

[0004] For the Littman structure, it introduces the loss of twice grating diffraction, and dissipates the-1st order diffraction energy, resulting in low feedback efficiency and low output efficiency, so it cannot detect large-area objects with high brightness. Therefore, there is still room for further improvement in power efficiency. In addition, in most application scenarios, the laser needs to have extremely high wavelength, power stability, long-term working reliability and strong temperature drift resistance, and the existing structure is difficult to meet all these performance requirements at the same time. In high-precision coherent applications, mode hopping during the tuning process is an important factor affecting performance stability, so the external cavity structure needs to be optimized to avoid mode hopping as much as possible. SUMMARY

[0005] In view of the above defects or improvement needs of the prior art, the present application provides an external cavity tunable laser linewidth compression system based on mutual injection of gain chips to realize wavelength phase locking, thereby solving the technical problems of low output infrared light power, poor stability and narrow jump-free tuning range of the prior art, and realizing high-power, narrow-linewidth, high-stability, large-range continuous tuning without mode hopping.

[0006] To achieve the above object, according to one aspect of the present application, there is provided an external cavity tunable laser linewidth compression system based on wavelength phase locking realized by mutual injection of gain chips, comprising a red light semiconductor laser main gain chip, a first collimating optical system, a blazed grating, a tuning rotating mirror, a mirror, a power driving system and a double-loop feedback amplification system; the double-loop feedback amplification system comprises a first secondary gain chip, a second secondary gain chip, a second collimating optical system, a third collimating optical system and a non-polarization beam splitter prism.

[0007] The first collimating optical system is used for collimating the laser emitted by the red light semiconductor laser main gain chip; the blazed grating is used for diffracting the collimated laser; the tuning rotating mirror is used for receiving a part of the laser diffracted by the blazed grating; the non-polarization beam splitter prism is used for receiving the remaining part of the laser diffracted by the blazed grating; the tuning rotating mirror is used for reflecting the laser vertically incident to the tuning rotating mirror; the mirror is located between the blazed grating and the tuning rotating mirror, and the plane where the mirror is located is perpendicular to the blazed grating.

[0008] The non-polarization beam splitter prism, the second collimating optical system and the first secondary gain chip are located on the optical path of the remaining part of the laser, and the second collimating optical system is located between the non-polarization beam splitter prism and the first secondary gain chip; the non-polarization beam splitter prism, the third collimating optical system and the second secondary gain chip are located on the same straight line, and the third collimating optical system is located between the non-polarization beam splitter prism and the second secondary gain chip; the first secondary gain chip and the second secondary gain chip are symmetric about the plane of the beam splitter film of the non-polarization beam splitter prism.

[0009] The red light semiconductor laser main gain chip, the first secondary gain chip and the second secondary gain chip are connected with the power driving system.

[0010] Preferably, the first collimating optical system, the second collimating optical system and the third collimating optical system each comprise a fast-axis collimating mirror surface and a slow-axis mirror surface.

[0011] Preferably, the polarization direction of the laser output by the gain chip is perpendicular to the grating ruling lines of the blazed grating; and the included angle between the laser collimated by the first collimating optical system and the blazed grating is 5-10°.

[0012] Preferably, the optical path distance from the red light semiconductor laser main gain chip to the blazed grating is 2-3 cm.

[0013] Preferably, the non-polarization beam splitter prism is a 50% non-polarization beam splitter prism.

[0014] Preferably, the remaining part of the laser is incident at an angle of 45° with the beam-splitting film of the 50% unpolarized beam-splitting prism.

[0015] Preferably, the homogenization output system comprises a first beam homogenization waveguide, a second beam homogenization waveguide, a half-transmission half-reflection mirror and a full reflection mirror; the full reflection mirror, the half-transmission half-reflection mirror, the unpolarized beam-splitting prism and the third collimating optical system are located on the same straight line and are sequentially arranged from top to bottom; the first beam homogenization waveguide is located on the path of the light reflected by the half-transmission half-reflection mirror; the second beam homogenization waveguide is located on the path of the light reflected by the full reflection mirror.

[0016] Preferably, the tuning mirror is fixed on a piezoelectric ceramic, and the piezoelectric ceramic is connected to a piezoelectric driving control system, which is used to drive the piezoelectric ceramic to drive the tuning mirror to rotate.

[0017] Preferably, the red semiconductor laser main gain chip, the blazed grating and the tuning mirror intersect on the same straight line in the plane, and the straight line is defined as the rotation axis, the tuning mirror rotates around the rotation axis, and the angle between the blazed grating and the tuning mirror is 25°-40°.

[0018] Preferably, the line symmetric to the mirror with respect to the rotation axis is defined as a virtual rotation axis, and the virtual rotation axis is located in the plane where the first secondary gain chip is located.

[0019] Overall, compared with the prior art, the above technical solutions conceived by the present application can achieve the following beneficial effects:

[0020] (1) The application couples gain structures of primary and secondary red light semiconductor gain chips, combines mutual injection feedback channels, makes multiple chips work in the same mode, significantly improves the overall output power of the system, breaks through the power bottleneck of single-chip external cavity, meets the demand of high-brightness application, and breaks through the upper limit of single gain chip external cavity laser output power. The application injects the 0-level light output by the primary chip into two secondary gain chips for amplification again, and at the same time, the light output by the secondary chips is fed back to the active region of the primary chip, forming a mutual injection phase locking relationship between the primary and secondary chips, realizing the forced synchronization of frequency and phase between multiple gain chips, greatly improving the coherence and output stability of the system, constructing a mutual injection feedback mechanism, and realizing the phase locking of the primary and secondary chips. The application greatly compresses the laser linewidth through the mutual injection locking mechanism combined with the Littman primary / secondary chip exclusive mode selection mechanism: the Littman structure provides strong wavelength selectivity of external cavity feedback, forms the exclusive feedback loop of the primary and secondary chips respectively, improves the single-mode output performance of each chip itself, and further reduces the frequency noise by combining the multi-chip phase locking mechanism to weaken the random phase disturbance, so that the laser linewidth can be compressed to tens of kilohertz or below, the spectral purity is greatly improved, and the laser output coherence is improved. The mutual injection phase locking mechanism significantly improves the output wavelength stability and temperature drift suppression capability, and combined with the multi-chip synchronous driving control system, the wavelength stability can be maintained for a long time, meeting the long-time continuous operation demand of precision measurement and other applications.

[0021] (2) The application limits the angle between the laser grazing incidence blazed grating collimated by the first collimation optical system and the blazed grating to 5-10°, so as to increase the number of grating lines irradiated by the laser beam and improve the wavelength selection and linewidth compression capability of the grating; the polarization direction of the laser collimated by the first collimation optical system is perpendicular to the grating lines of the blazed grating, so as to ensure that the laser is TM polarized to obtain the highest blazed grating diffraction efficiency. The application limits the optical path distance from the red light semiconductor laser primary gain chip (1) to the blazed grating to 2-3 cm, so as to leave sufficient space for the beam collimation system and ensure the compactness of the system.

[0022] The purpose of the application that the laser is incident to the non-polarization beam splitter prism and the beam splitter film of the non-polarization beam splitter prism at an angle of 45° is to ensure that the non-polarization beam splitter prism works in the state of the lowest polarization dependence and the most uniform beam splitting; the non-polarization beam splitter prism is limited to a 50% non-polarization beam splitter, so as to balance the gain provided by the secondary gain chip, match the mode and power of the two lasers in the double feedback amplification system, and improve the coupling efficiency of the system.

[0023] (3) The application limits that the tuning rotating mirror rotates around the rotating shaft, and the included angle between the blazed grating and the tuning rotating mirror is 25-40°. By precisely controlling the angle and position of the tuning rotating mirror, a wide-range mode-hop-free wavelength tuning is realized. By precisely designing the position of the rotating shaft of the tuning rotating mirror and precisely controlling the rotation of the mirror by using a piezoelectric ceramic driving device, continuous and precise adjustment of the feedback wavelength is realized, the mode-hop phenomenon in the tuning process is effectively avoided, and the tuning precision, range and stability of the output laser are ensured. The purpose of limiting that the virtual rotating shaft is located in the plane where the first secondary gain chip is located is to ensure that the resonance order of the exclusive feedback loop of the secondary gain chip is unchanged, and to avoid the mode-hop phenomenon of the secondary gain chip in the tuning process.

[0024] (4) The application guides the output laser into the homogenization waveguide through the half-transmission half-reflection mirror and the full reflection mirror to form a consistent and energy-distributed uniform circular coherent light spot, which can be directly used for large-area high-brightness interference measurement, has good application docking capability, and can obtain a high-quality and uniform light beam. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 is the overall structure principle diagram of embodiment 1 of the application.

[0026] Figure 2 is the grating diffraction feedback injection principle diagram of embodiment 2 of the application.

[0027] Figure 3 is the double-path feedback amplification principle diagram of embodiment 2 of the application.

[0028] Figure 4 is the secondary gain chip injection principle diagram of embodiment 2 of the application.

[0029] Figure 5 is the wavelength mode-hop-free tuning principle diagram of embodiment 2 of the application.

[0030] Figure 6 is the homogenization coherent output principle diagram of embodiment 2 of the application.

[0031] In all the drawings, the same reference signs are used to represent the same elements or structures, wherein:

[0032] 1, red light semiconductor laser main gain chip; 2, first collimation optical system; 3, double-path feedback amplification system; 4, blazed grating; 5, tuning rotating mirror; 6, piezoelectric ceramic; 7, mirror; 8, non-polarization beam splitter prism; 9, second collimation optical system; 11, first secondary gain chip; 12, power driving system; 13, third collimation optical system; 15, second secondary gain chip; 16, piezoelectric driving control system; 17, half-transmission half-reflection mirror; 18, first light beam homogenization waveguide; 19, full reflection mirror; 20, second light beam homogenization waveguide. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0034] Example 1

[0035] This embodiment provides an external cavity tunable laser linewidth compression system based on wavelength phase locking achieved through mutual injection of gain chips, such as... Figure 1 As shown, the system includes a red semiconductor laser main gain chip 1, a first collimating optical system 2, a blazed grating 4, a tuning mirror 5, a reflector 7, a power supply drive system 12, a dual-path feedback amplification system 3, a first beam homogenizing waveguide 18, a second beam homogenizing waveguide 20, a semi-transparent and semi-reflective mirror 17, and a total reflection mirror 19; the dual-path feedback amplification system 3 includes a first-stage gain chip 11, a second-stage gain chip 15, a second collimating optical system 9, a third collimating optical system 13, and a 50% unpolarized beam splitter prism 8;

[0036] The first collimating optical system 2 is used to collimate the laser emitted by the red semiconductor laser main gain chip 1; the blazed grating 4 is used to diffract the collimated laser, and a portion of the diffracted laser is incident on the tuning mirror 5, while the remaining portion is incident on the 50% unpolarized beam splitter 8; the tuning mirror 5 is used to reflect a portion of the laser perpendicularly incident on the tuning mirror 5 along the original path; the reflecting mirror 7 is located between the blazed grating 4 and the tuning mirror 5, and the plane of the reflecting mirror 7 is perpendicular to the blazed grating 4;

[0037] The 50% unpolarized beam splitter prism 8, the second collimating optical system 9, and the first-stage gain chip 11 are all located on the extension line of the line containing the remaining portion of the laser beam, and the second collimating optical system 9 is located between the 50% unpolarized beam splitter prism 8 and the first-stage gain chip 11; the 50% unpolarized beam splitter prism 8, the third collimating optical system 13, and the second-stage gain chip 15 are located on the same straight line, and the third collimating optical system 13 is located between the 50% unpolarized beam splitter prism 8 and the second-stage gain chip 15; the first-stage gain chip 11 and the second-stage gain chip 15 are symmetrical about the beam splitting film of the 50% unpolarized beam splitter prism 8;

[0038] The red light semiconductor laser main gain chip 1, the first secondary gain chip 11 and the second secondary gain chip 15 are connected with the power supply driving system 12. The first collimating optical system 2, the second collimating optical system 9 and the third collimating optical system 13 each include a fast-axis collimating mirror and a slow-axis mirror. The angle between the laser collimated by the first collimating optical system 2 and the blazed grating 4 is 10°; the polarization direction of the laser collimated by the first collimating optical system 2 is perpendicular to the grating lines of the blazed grating 4. The optical path distance from the red light semiconductor laser main gain chip 1 to the blazed grating is 2 cm. The remaining laser is incident at an angle of 45° with the beam-splitting film of the 50% non-polarizing beam splitter 8. The 50% non-polarizing beam splitter 8, the semi-transparent mirror 17, the full mirror 19 and the second secondary gain chip 15 are located on the same straight line, and the semi-transparent mirror 17 is located between the 50% non-polarizing beam splitter 8 and the full mirror 19; the first beam homogenization waveguide 18 is located on the path of the reflected light of the semi-transparent mirror 17; the second beam homogenization waveguide 20 is located on the path of the reflected light of the full mirror 19.

[0039] The tuning mirror 5 is fixed on the piezoelectric ceramic 6, the piezoelectric ceramic 6 is connected with the piezoelectric driving control system 16, and the piezoelectric driving control system 16 is used to drive the piezoelectric ceramic 6 to drive the tuning mirror 5 to rotate. The red light semiconductor laser main gain chip 1, the blazed grating 4 and the tuning mirror 5 intersect on the same straight line, and the straight line is recorded as the rotation axis; the tuning mirror 5 rotates around the rotation axis, and the angle between the blazed grating 4 and the tuning mirror 5 is 32°. The line symmetric to the mirror 7 about the rotation axis is recorded as the virtual rotation axis, and the virtual rotation axis is located in the plane where the first secondary gain chip 11 is located.

[0040] Working principle: the TM polarized laser emitted by the red light semiconductor laser main gain chip 1 is collimated by the fast axis collimating cylindrical lens and the slow axis collimating cylindrical lens, and then is incident on the blazed grating 4, and the polarization direction is perpendicular to the ruling direction of the grating. The grating 4 diffracts most of the laser energy to the 0th order (path S4) and the 1st order (path S2): the laser of the path S2 is incident on the tuning turning mirror 5, and the angle perpendicular to the specific wavelength of the tuning turning mirror 5 will be reflected to return to the blazed grating 4 by the original light path for secondary diffraction, part of which is fed back to the active region of the red light semiconductor laser main gain chip 1 (main gain chip) along the path S1, and the other part is changed in direction by the mirror 7 perpendicular to the blazed grating 4 after being incident on the tuning turning mirror 5, and then the energy is divided into the reflected light along the path S2 and the 0th order diffracted light along the path S4, and the 0th order diffracted light along the path S4 is output to the subsequent double-path feedback amplification system 3, and after being divided into two beams by the 50% non-polarization beam splitter prism 8, the two beams are focused and matched with the active region transverse mode by the second collimating optical system 9 and the third collimating optical system 13 respectively, and then are coupled into the first secondary gain chip 11 and the second secondary gain chip 15 which are placed in the same polarization as the main gain chip for amplification feedback. The output light after amplification is also collimated by the second collimating optical system 9 and the third collimating optical system 13, and then is combined by the 50% non-polarization beam splitter prism 8, and 50% of the energy is output to the subsequent homogenization output system through the upper end surface, and the other 50% of the energy is fed back to the blazed grating 4 along the path S4. The 1st order diffracted part of the feedback light is diffracted along the light path of the diffracted light beam 3 to select the diffraction angle-wavelength, compress the linewidth, and the 0th order diffracted part returns to the active region of the main gain chip 1 along the path S1. The laser is output to the homogenization output system through the upper end surface of the 50% non-polarization beam splitter prism 8, and is split by the half-transmission half-reflection mirror 17, and the collimated laser beams are coupled into the first beam homogenization waveguide 18 and the full reflection mirror 19 respectively, and the laser transported into the first beam homogenization waveguide 18 is subjected to spot homogenization, and the laser transported into the full reflection mirror 19 is all output to the second beam homogenization waveguide 20 for spot homogenization, and a double-path circular coherent output is obtained, which can be directly used for subsequent coherent measurement.

[0041] The red light semiconductor laser main gain chip 1 receives the energy of specific wavelength output by the grating 4 feedback and the double-path amplification feedback system 3, and the wavelength is reduced in the threshold of the active region, so that the specific wavelength occupies the mode competition advantage, so that the main gain chip 1 realizes the narrow line width output of the specific wavelength; and the first secondary gain chip 11 and the second secondary gain chip 15 in the double-path feedback amplification system 3 receive the specific wavelength narrow line width energy output by the grating 4 feedback and the main gain chip 1, so that the specific wavelength also occupies the competition advantage, so that the line width of the first secondary gain chip 11 and the second secondary gain chip 15 is reduced, and the same specific wavelength narrow line width laser is output, and the process is called mutual injection wavelength locking between the main and secondary gain chips. In addition, the red light semiconductor laser main gain chip 1, the first secondary gain chip 11 and the second secondary gain chip 15 are driven by the power supply driving system 12 at the same time, so as to ensure that the working state parameters such as injection current, phase, temperature and center wavelength of the three are consistent, and the three work together in the external cavity structure.

[0042] The tuning rotating mirror 5 is fixed on the piezoelectric ceramic 6 driven by the piezoelectric driving control system 16, and the control system 16 changes the voltage of the piezoelectric ceramic 6 to make it stretch and shrink, so as to drive the tuning rotating mirror 5 to rotate around the rotation point by a certain angle, so that the tuning rotating mirror 5 reflects the light beam of another specific diffraction angle, so as to change the wavelength component fed back to the red light semiconductor laser main gain chip 1, the first secondary gain chip 11 and the second secondary gain chip 15, establish a new active region dominant mode, and realize the wavelength tuning of the external cavity narrow line width laser output.

[0043] Embodiment 2

[0044] The embodiment provides an external cavity tunable laser line width compression system based on mutual injection of gain chips to realize wavelength phase locking, which comprises a red light semiconductor laser main gain chip 1, a first collimating optical system 2, a blazed grating 4, a tuning rotating mirror 5, a reflecting mirror 7, a power supply driving system 12, a double-path feedback amplification system 3, a first beam homogenization waveguide 18, a second beam homogenization waveguide 20, a semi-transparent semi-reflective mirror 17 and a full-reflective mirror 19; the double-path feedback amplification system 3 comprises a first secondary gain chip 11, a second secondary gain chip 15, a second collimating optical system 9, a third collimating optical system 13 and a non-polarization beam splitting prism 8.

[0045] The first collimating optical system 2 is used for collimating the laser emitted by the red light semiconductor laser main gain chip 1; the blazed grating 4 is used for diffracting the collimated laser, and part of the diffracted laser is incident on the tuning rotating mirror 5, and the remaining laser is incident on the 50% non-polarization beam splitting prism 8; the tuning rotating mirror 5 is used for reflecting the part of the laser vertically incident on the tuning rotating mirror 5 in the original path; the reflecting mirror 7 is located between the blazed grating 4 and the tuning rotating mirror 5, and the extension line of the reflecting mirror 7 is perpendicular to the blazed grating 4;

[0046] The 50% non-polarizing beam splitter prism 8, the second collimating optical system 9 and the first secondary gain chip 11 are located on the extension line of the straight line where the residual laser is located, and the second collimating optical system 9 is located between the 50% non-polarizing beam splitter prism 8 and the first secondary gain chip 11; the 50% non-polarizing beam splitter prism 8, the third collimating optical system 13 and the second secondary gain chip 15 are located on the same straight line, and the third collimating optical system 13 is located between the 50% non-polarizing beam splitter prism 8 and the second secondary gain chip 15; the first secondary gain chip 11 and the second secondary gain chip 15 are symmetric about the beam splitting film plane of the 50% non-polarizing beam splitter prism 8;

[0047] The red light semiconductor laser main gain chip 1, the first secondary gain chip 11 and the second secondary gain chip 15 are connected with the power driving system 12. The first collimating optical system 2, the second collimating optical system 9 and the third collimating optical system 13 each include a fast-axis collimating mirror surface and a slow-axis mirror surface. The angle between the laser collimated by the first collimating optical system 2 and the blazed grating 4 is 10°; the polarization direction of the laser collimated by the first collimating optical system 2 is perpendicular to the grating ruling line of the blazed grating 4. The optical path distance from the red light semiconductor laser main gain chip 1 to the blazed grating is 3 cm. The residual laser is incident at an angle of 45° with the beam splitting film of the non-polarizing beam splitter prism 8. The non-polarizing beam splitter prism 8, the semi-transparent semi-reflective mirror 17, the full-reflective mirror 19 and the second secondary gain chip 15 are located on the same straight line, and the semi-transparent semi-reflective mirror 17 is located between the non-polarizing beam splitter prism 8 and the full-reflective mirror 19; the first beam homogenization waveguide 18 is located on the path where the light reflected by the semi-transparent semi-reflective mirror 17 is located; the second beam homogenization waveguide 20 is located on the path where the light reflected by the full-reflective mirror 19 is located.

[0048] The tuning turning mirror 5 is fixed on the piezoelectric ceramic 6, the piezoelectric ceramic 6 is connected with the piezoelectric driving control system 16, and the piezoelectric driving control system 16 is used to drive the piezoelectric ceramic 6, thereby driving the tuning turning mirror 5 to rotate. The red light semiconductor laser main gain chip 1, the blazed grating 4 and the tuning turning mirror 5 intersect on the same straight line, and the straight line is recorded as a rotation axis; the tuning turning mirror 5 rotates around the rotation axis, and the angle between the blazed grating 4 and the tuning turning mirror 5 is 40°. The line symmetric to the reflection mirror 7 about the rotation axis is recorded as a virtual rotation axis, and the virtual rotation axis is located in the plane where the first secondary gain chip 11 is located.

[0049] In this example, as Figure 2The grating diffraction feedback injection principle is shown. The laser light incident along path S1 is diffracted by grating 4, and part of the laser light is output to the two-way feedback system 3 through 0-order diffraction path S4, and the remaining laser light is incident on tuning mirror 5 along path S2 through 1-order diffraction. The components of a specific wavelength in path S2 are reflected vertically to tuning mirror 5. Part of the reflected specific wavelength energy is fed back to the active region of the gain chip 1 along path S1 through 1-order diffraction, and the other part of the laser light is diffracted through 0-order diffraction to path S3 and reflected by the mirror 7 perpendicular to the grating 4, and then undergoes the same diffraction angle-wavelength selection process as path S2. After the feedback light in path S3 is incident on the grating 4, part of the laser light is diffracted through 0-order diffraction back to path S2, and the remaining laser light is diffracted through 1-order diffraction along path S4 and incident into the two-way feedback system. The output light of the two-way feedback system is the same as the output light of the gain chip 1, and part of it is along paths S2, S3, S4 through the cooperation of the blazed grating 4, the tuning mirror 5, and the mirror 7 for linewidth compression and feedback, and part of it is injected into the gain chip 1 along path S1 to form mutual injection locking between the gain chip and the two-way amplification feedback system.

[0050] In this example, as shown in Figure 3 The two-way amplification feedback system principle is shown. The narrow linewidth laser light emitted along path S4 is first divided into two beams a and b of the same size by a 50% non-polarization beam splitter prism 8. The two beams of light are coupled into the active regions of the first secondary gain chip 11 and the second secondary gain chip 15 through the second collimating optical system 9 and the third collimating optical system 13, respectively, after transmitting the same optical path. After amplification in the first secondary gain chip 11 and the second secondary gain chip 15, the laser light is fed back along the original path and collimated along the fast and slow axes through the second collimating optical system 9 and the third collimating optical system 13, respectively. The collimated amplified light is incident on the 50% non-polarization beam splitter prism 8, and half of the energy is fed back along path S4, and the other half of the energy is output as an external cavity output window through the c port of the 50% non-polarization beam splitter prism 8.

[0051] In this example, as shown in Figure 4 The gain chip injection principle is shown. Taking the first secondary gain chip 11 as an example (the second secondary gain chip 15 is the same), the feedback from the blazed grating 4 and the output of the red semiconductor laser main gain chip 1 are emitted along path S4. Only the diffracted light of a specific wavelength has a transmission direction that coincides with the main optical axis direction of the second collimating optical system 9, and after being focused along the slow and fast axes, respectively, the transverse mode and the active region are matched, and the light is successfully coupled into the first secondary gain chip 11 for amplification. Adjusting the voltage across the piezoelectric ceramic 6 drives the tuning mirror 5 to rotate, which can select different diffraction angles, i.e., different specific wavelength beams are injected into the active region of the gain chip, so that the wavelength has a mode competition advantage in the external cavity.

[0052] In this example, as shown in Figure 5The diagram illustrates the principle of wavelength-free mode-hopping tuning. The laser beams output from the red semiconductor laser main gain chip 1, the first-stage gain chip 11, and the second-stage gain chip 15 are diffracted by the +1st order of the blazed grating 4 and then incident on the tuning mirror 5. During this process, only beams of a specific wavelength can be perpendicularly incident on the mirror 5, and then reflected back to the grating 4 for secondary diffraction. Only components of the same specific wavelength, after diffraction, satisfy the chip injection conditions, allowing for... Figure 4 The successful feedback or injection into the active region of the gain chip provides a mode competition advantage, while light of other wavelength components cannot obtain gain, ultimately ensuring a narrow linewidth and high coherence laser output from the external cavity. The tuning mirror 5 is connected to the piezoelectric ceramic 6 controlled by the piezoelectric drive control system 16, allowing the tuning mirror 5 to rotate around an axis that intersects the plane of the blazed grating 4, the rear end face of the red semiconductor laser main gain chip 1, and the tuning mirror 5. This configuration allows the tuning mirror 5 to maintain the resonant order of the external cavity during rotation, thereby suppressing mode hopping. The feedback optical paths of gain chips 11 and 15 can be equivalent to the feedback optical path of the red semiconductor laser main gain chip 1 symmetrical along the reflector 7. Similarly, the axis of the symmetrical virtual tuning mirror is located on the intersection of the rear end face of the gain chip 11 and the plane of the grating 4. The optical path of the second-stage gain chip 15 from the 50% unpolarized beam splitter 8 is equal to the optical path of the first-stage gain chip 11 from the 50% unpolarized beam splitter 8. In terms of tuning, the voltage of the piezoelectric ceramic 6 is controlled by the piezoelectric drive control system 16, thereby driving the tuning mirror 5 to rotate around the axis, changing the wavelength composition of the diffracted light that can be fed back by the grating. This allows energy of different specific wavelengths to be fed back and injected into the red semiconductor laser main gain chip 1, the first-stage gain chip 11, and the second-stage gain chip 15, so that the new wavelength gains a gain advantage in the external cavity, thereby changing the wavelength composition of the narrow linewidth output of the external cavity. The line symmetrical about the rotating axis with respect to the reflector 7 is denoted as the virtual rotating axis, which is located in the plane where the first-stage gain chip 11 is located.

[0053] In this example, as Figure 6 The diagram shows the principle of homogenized coherent output. A narrow-linewidth laser beam is output from the upper surface of the prism, with a spot shape that is elliptical, similar to that of a collimated edge-emitting semiconductor laser. The laser beam is split by a semi-transparent mirror 17. The split beams are coupled into flexible beam homogenization waveguides 18 and 20, respectively, to obtain a circular dual-path coherent homogenized spatial output.

[0054] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. An external cavity tunable laser linewidth compression system based on wavelength phase locking achieved by mutual injection of gain chips, characterized in that, The application relates to a red light semiconductor laser device, which comprises a red light semiconductor laser main gain chip (1), a first collimating optical system (2), a blazed grating (4), a tuning rotating mirror (5), a reflecting mirror (7), a power driving system (12) and a double-path feedback amplification system (3); the double-path feedback amplification system (3) comprises a first secondary gain chip (11), a second secondary gain chip (15), a second collimating optical system (9), a third collimating optical system (13) and a non-polarization beam splitting prism (8). The first collimating optical system (2) is used for collimating the laser emitted by the red light semiconductor laser main gain chip (1); the blazed grating (4) is used for diffracting the collimated laser; the tuning rotating mirror (5) is used for receiving part of the laser diffracted by the blazed grating (4); the non-polarization beam splitting prism (8) is used for receiving the remaining part of the laser diffracted by the blazed grating (4); the tuning rotating mirror (5) is used for reflecting the laser vertically incident to the tuning rotating mirror (5) in the original path; the reflecting mirror (7) is located between the blazed grating (4) and the tuning rotating mirror (5), and the plane where the reflecting mirror (7) is located is perpendicular to the blazed grating (4). The non-polarization beam splitting prism (8), the second collimating optical system (9) and the first secondary gain chip (11) are located on the light path of the remaining part of the laser, and the second collimating optical system (9) is located between the non-polarization beam splitting prism (8) and the first secondary gain chip (11); the non-polarization beam splitting prism (8), the third collimating optical system (13) and the second secondary gain chip (15) are located on the same straight line, and the third collimating optical system (13) is located between the non-polarization beam splitting prism (8) and the second secondary gain chip (15); the first secondary gain chip (11) and the second secondary gain chip (15) are symmetric about the beam splitting film plane of the non-polarization beam splitting prism (8); The red light semiconductor laser main gain chip (1), the first secondary gain chip (11) and the second secondary gain chip (15) are connected with the power driving system (12).

2. The external cavity tunable laser linewidth compression system based on mutual injection of gain chips to realize wavelength phase locking of claim 1, wherein, The first collimating optical system (2), the second collimating optical system (9) and the third collimating optical system (13) all comprise a fast-axis collimating mirror surface and a slow-axis mirror surface.

3. The external cavity tunable laser linewidth compression system based on mutual injection of gain chips to realize wavelength phase locking of claim 1, wherein, The polarization direction of the laser output by the gain chip (1) is perpendicular to the grating ruling line of the blazed grating (4); the included angle between the collimated laser after the first collimating optical system (2) and the blazed grating (4) is 5-10 degrees.

4. The external cavity tunable laser linewidth compression system based on mutual injection of gain chips to realize wavelength phase locking of claim 1, wherein, The optical path distance from the red light semiconductor laser main gain chip (1) to the blazed grating is 2-3 cm.

5. The external cavity tunable laser linewidth compression system based on mutual injection of gain chips to realize wavelength phase locking of claim 1, wherein, The non-polarization beam splitting prism (8) is a 50% non-polarization beam splitting prism.

6. The external cavity tunable laser linewidth compression system based on mutual injection of gain chips to realize wavelength phase locking of claim 5, wherein, The remaining part of the laser is incident at an angle of 45 degrees to the beam splitting film of the 50% non-polarization beam splitting prism.

7. The external cavity tunable laser linewidth compression system based on mutual injection of gain chips to realize wavelength phase locking of claim 1, wherein, The homogenization output system comprises a first light beam homogenization waveguide (18), a second light beam homogenization waveguide (20), a semi-transmissive semi-reflective mirror (17) and a full reflective mirror (19); the full reflective mirror (19), the semi-transmissive semi-reflective mirror (17), the non-polarization beam splitter prism (8) and the third collimating optical system (13) are located on the same straight line and are sequentially arranged from top to bottom; the first light beam homogenization waveguide (18) is located on the path of the reflected light of the semi-transmissive semi-reflective mirror (17); the second light beam homogenization waveguide (20) is located on the path of the reflected light of the full reflective mirror (19).

8. The external cavity tunable laser linewidth compression system based on mutual injection of gain chips to achieve wavelength phase locking of claim 1, wherein, The tuning rotating mirror (5) is fixed on a piezoelectric ceramic (6), and the piezoelectric ceramic (6) is connected with a piezoelectric driving control system (16) for driving the piezoelectric ceramic (6) to drive the tuning rotating mirror (5) to rotate.

9. The external cavity tunable laser linewidth compression system based on mutual injection of gain chips to achieve wavelength phase locking of claim 1, wherein, The red light semiconductor laser main gain chip (1), the blazed grating (4) and the tuning rotating mirror (5) are located on the same straight line intersecting with the plane, and the straight line is recorded as a rotating shaft, the tuning rotating mirror (5) rotates around the rotating shaft; the included angle between the blazed grating (4) and the tuning rotating mirror (5) is 25°-40°.

10. The external cavity tunable laser linewidth compression system based on mutual injection of gain chips to realize wavelength phase locking of claim 9, wherein, A line symmetric to the reflecting mirror (7) about the rotating shaft is recorded as a virtual rotating shaft, and the virtual rotating shaft is located in the plane where the first secondary gain chip (11) is located.

Images