CN103219651A - Semiconductor laser light source based on coherent polarization synthetic technology - Google Patents

Abstract

The invention relates to a semiconductor laser light source based on coherent polarization synthesis technology, comprising: a master laser and multiple slave lasers, the seed light emitted by the master laser is divided into multiple paths after passing through a beam splitter, and injected into multiple slave lasers respectively to realize Phase locking of the slave laser; each laser emitted from the laser is polarized and synthesized in the polarization beam combining prism with another laser emitted from the laser or polarized and synthesized, which has been subjected to the action of a half-wave plate. In the semiconductor laser light source based on the coherent polarization synthesis technology of the present invention, the number of lasers can be determined according to the total power of the laser and the power of a single laser; ordinary polarization synthesis can only synthesize two lasers, and the present invention uses the phase of the laser Modulation can expand the number of combined beams to an infinite number, which is very flexible.

Description

Semiconductor laser light source based on coherent polarization synthesis technology

technical field

The invention relates to the field of semiconductor laser beam combining light sources, in particular to a semiconductor laser light source based on coherent polarization combining technology.

Background technique

Due to the advantages of small size, light weight, high reliability, and high electro-optical conversion efficiency, semiconductor lasers not only become the core light source in the fields of laser processing, laser medical treatment, laser display, laser monitoring, laser ranging, laser guidance, and laser fuze. And supporting technologies, and also gain more and more attractive application prospects in the fields of laser radar, laser gas detection, laser ranging and other fields. The application of semiconductor lasers greatly reduces the complexity of the overall system in these applications and greatly improves its reliability. However, in applications such as lidar and active detection and identification, it is necessary to measure the fine parameters of the target (vibration, rotation, precession, nutation, etc.), and the light source must be coherent light. Ordinary high-power semiconductor lasers usually operate in saturation mode, with multi-mode output and poor coherence. Semiconductor lasers that can realize single longitudinal mode operation have good coherence and long coherence length (coherence length is an important indicator of coherent light source, mainly determined by the laser frequency linewidth), which can reach tens of kilometers, but the output power is in hundreds of kilometers. The milliwatt level is difficult to meet the requirements for high power output in the above applications.

Semiconductor laser coherent combination technology is an effective way to obtain high-power coherent light sources. It usually refers to a group of laser units that have the same frequency, consistent polarization, and phase to form a fixed relationship through certain means, so that the overall light field presents a coherent superposition. Phenomenon. According to the schemes of coherent combination of semiconductor lasers reported so far, there are mainly the following forms: (1) Coherent combination is realized by self-organization between units such as evanescent waves and leaky waves. It mainly relies on the leaky mode (leaked wave, evanescent wave, etc.) between the units to form an adaptive and stable phase-lock in the waveguide, so as to realize the coherent combination of the beams between the units. This method strongly depends on the frequency narrowing effect and phase selective locking effect of the waveguide and laser resonator coupling system, and has relatively strict requirements on the structure of the laser. (2) Adopt external cavity phase-locking technology to realize coherent beam combining. External cavity phase locking is mainly to form a new resonant cavity outside the semiconductor laser array. Through the diffraction effect and the reflection of the external cavity mirror, the various light-emitting units are fully coupled to each other, and the phase of each laser light-emitting unit is locked, so that the semiconductor laser coherent output. (3) Adopt master-slave injection technology to realize coherent synthesis. The master-slave injection technology is to inject a low-power, narrow-linewidth semiconductor laser (master laser) as a seed source into an ordinary semiconductor laser array (slave laser). Under certain conditions, the free-running mode of the slave laser is suppressed. A stable oscillation is established at the frequency of the injected light, so that each unit in the array operates at the same frequency as the main laser, achieving the purpose of phase locking and coherence. In (2) and (3), due to the inconsistency of the spectrum of each luminous point, the spectrum of the obtained coherent laser cannot be compressed into a single longitudinal mode, and the line width is wide. Due to the shortcomings of the above scheme, such as special laser structure, complex preparation process, and different spectrum of beam combining units, it is difficult to meet the requirements of coherent combining light sources in terms of spectral line width and output power at the same time. The main technical bottlenecks in applications such as detection and identification, laser gas detection, etc.

Contents of the invention

In order to solve the current situation that the existing semiconductor laser coherent synthesis light source is difficult to meet the application requirements in terms of spectral linewidth and output power, the present invention provides a semiconductor laser light source based on coherent polarization synthesis technology that can achieve high power and narrow linewidth.

Technical scheme of the present invention is specifically as follows:

Semiconductor laser light sources based on coherent polarization synthesis technology, including:

A master laser and a plurality of slave lasers, the seed light emitted by the master laser is divided into multiple paths after passing through a beam splitter, and injected into a plurality of slave lasers respectively to achieve phase locking of the slave lasers; each laser emitted from the slave laser is connected to The other laser emitted from the laser or polarized and synthesized, through the action of a half-wave plate, is polarized and synthesized in the polarization beam combining prism;

A photodetector, the photodetector is used for real-time monitoring of the combined light beam after polarization combination, and can transmit the signal to the phase control module; the phase control module demodulates the phase error of the two beams of light, and feeds back the control signal Give the phase modulator to perform phase modulation on each beam emitted from the laser, control the phase difference of the two beams participating in the polarization combination to an integer multiple of π and keep it as linearly polarized light, so as to continue polarization combination with the next beam beam to achieve coherent polarization combining.

In the above technical solution, all master and slave lasers are fixed on the same plane.

In the above technical solution, collimating mirrors for reducing the divergence angle of the lasers and performing collimation are respectively installed in front of the master and slave lasers.

In the above technical solution, the seed light emitted by the master laser is divided into multiple paths by the dichroic prism, and injected into multiple slave lasers through the action of the total reflection mirror and the reflection plate; Reflective flat plate or reflective prism.

In the above technical solution, the seed light emitted by the master laser is divided into multiple paths by a dichroic prism, and injected into multiple slave lasers through the action of a total reflection mirror and a reflective plate; the reflective plate is a parallel plate with a certain reflectivity , reflectance values from 1% to 50%.

In the above technical solution, the front cavity surface of the slave laser is coated with an anti-reflection coating with a reflectivity above 99%, so as to ensure a high injection rate of the seed light.

In the above technical solution, the phase control module used includes a phase control circuit, a lock-in amplifier, and a signal generator.

In the above technical solution, the phase modulator is a lithium niobate (LiNbO ₃ ) phase modulator.

In the above technical solution, the number of the plurality of slave lasers is four.

The semiconductor laser light source based on the coherent polarization synthesis technology of the present invention has the following advantages:

The semiconductor laser light source based on coherent polarization synthesis technology of the present invention combines coherent synthesis and polarization synthesis technology, and makes multiple single transverse mode semiconductor lasers meet the coherence condition through master-slave injection phase-locking. The phase of the beam is controlled, and the coherent combination of multiple beams is realized by the method of polarization beam combining, and a coherent light source with high power and narrow linewidth can be obtained. This technology has no special structural requirements for the laser itself, and theoretically can realize the coherent combination of countless units, which is a very promising coherent combination technology.

In the semiconductor laser light source based on the coherent polarization synthesis technology of the present invention, the number of lasers can be determined according to the total power of the laser and the power of a single laser; ordinary polarization synthesis can only synthesize two lasers, and the present invention passes the phase of the laser Modulation can expand the number of combined beam lasers to an infinite number, which is very flexible.

Description of drawings

FIG. 1 is a schematic structural diagram of a semiconductor laser light source based on coherent polarization combining technology of the present invention.

Detailed ways

The inventive idea of the present invention is: the semiconductor laser light source based on the coherent polarization synthesis technology of the present invention includes a single-frequency semiconductor laser as the master laser, and multiple single-transverse-mode semiconductor lasers with the same wavelength and the same structure as the slave lasers; all lasers are Fix them on the same plane and arrange them according to the diagram. The anti-reflection coating is coated on the front cavity of the laser, and the transmittance is above 99%. All the light emitted by the master and slave lasers has a small divergence angle after passing through the collimating mirror. The seed light emitted by the main laser is divided into multiple seed beams of the same power after being split by a beam splitting prism with a splitting rate of 50%, and then injected into multiple slave beams through a total reflection mirror and a reflective plate (reflective rate of 10%). The laser thus achieves phase locking of the slave laser. An optical isolator is added between the master and slave lasers to ensure the one-way transmission of the seed light. After the slave laser is phase-locked, it emits a laser beam with the same frequency and the same vibration direction as the master laser. After the beam passes through the reflective plate, 90% of the beam is transmitted. The two beams are polarized and synthesized through the polarization beam combining prism, and the photodetector is used to monitor the synthesized beam in real time, and the signal is transmitted to the phase control circuit. The phase control circuit demodulates the phase error of the two beams, and the phase modulator Phase modulation is performed on each beam, and the phase difference of the two beams participating in polarization synthesis is controlled at an integer multiple of π and kept as linearly polarized light, so as to continue to perform polarization combining with the next beam, realizing the technology based on coherent polarization synthesis Semiconductor laser light source.

The present invention will be described in further detail below in conjunction with the embodiment given with accompanying drawing.

Fig. 1 shows a specific embodiment of the semiconductor laser light source based on coherent polarization combining technology of the present invention. With reference to Fig. 1, the semiconductor laser light source based on coherent polarization synthesis technology of the present invention comprises master laser 1, 4 slave lasers 2, collimating mirror 3, optical isolator 4, beam splitting prism 5 with 50% splitting rate, total reflection mirror 6 , reflecting plate 7 , phase control module 8 , phase modulator 9 , photodetector 10 , polarization beam combining prism 11 , and half-wave plate 12 . All the lasers are fixed in the same plane. The phase control module 8 used in the present invention includes a phase control circuit, a lock-in amplifier, and a signal generator, and the phase modulator is a lithium niobate phase modulator that can be used in a free optical path.

The semiconductor laser light source based on the coherent polarization synthesis technology of the present invention installs the collimating mirror 3 in front of the cavity of each laser through a six-axis precision adjustment frame and ultraviolet glue, so that the laser beam is collimated, and the collimating mirror can also be made by The mechanical mirror base is supported, and the collimating mirror and the mechanical mirror base are glued and fixed with ultraviolet glue. During the installation and adjustment of the collimator, it is necessary to check whether the far-field spot positions of all lasers are at the same height in the horizontal direction.

In the semiconductor laser light source based on the coherent polarization synthesis technology of the present invention, the dichroic prism 5 is formed by coating the oblique surfaces of the triangular prisms with a dichroic film, and then gluing the oblique surfaces of the two triangular prisms together. The surface of the total reflection mirror 6 is coated with a high-reflection film, the reflection plate is coated with a spectroscopic film with a reflectivity of 10% on one side, and the other surface is coated with an anti-reflective coating. The base material of all optical elements is fused silica. The optical element is clamped by a six-axis adjustment frame and an appropriate fixture for adjustment, so that it can split and reflect the light beam to meet the design requirements. After adjustment, fix it with UV glue or mechanical methods.

When the semiconductor laser light source based on the coherent polarization combining technology of the present invention performs polarization beam combining, the light emitted by all the lasers is collimated through the collimating mirror 3, and the seed light emitted by the main laser 1 is divided into four paths after passing through the beam splitter 5, Through the function of the total reflection mirror 6 and the reflective plate 7, four slave lasers are respectively injected to realize the phase locking of the slave lasers; the phase-locked slave laser emits a beam of the same frequency as the master laser, and then transmits through the reflective plate, and the transmitted beam The polarization synthesis is carried out sequentially through the polarization beam combining prism 11, the half-wave plate 12 is used to adjust the polarization direction of the beam, the photodetector 10 is used to monitor the combined beam in real time, and the signal is transmitted to the phase control module 8, and the phase control module demodulates The phase error of the two beams of light is obtained, and the phase modulation of each beam is carried out by the phase modulator 9, and the phase difference of the two beams participating in the polarization synthesis is controlled at an integer multiple of π and kept as linearly polarized light, thereby continuing with the following One beam is polarized and combined to realize coherent polarization combination.

Specifically:

First, the first laser light emitted from the laser 2 at the top passes through the first phase modulator 9 and then the first half-wave plate 12. After being reflected by the mirror, it enters the first polarization beam combiner In the prism 11, the laser beam emitted by the second slave laser 2 is polarized and combined.

Then, the laser beam that has been polarized and combined passes through the action of the second half-wave plate 12 , and then enters the second polarizing beam combining prism 11 , where it is polarized and combined with the laser beam emitted by the third laser 2 .

Finally, the laser beams that have been polarized and beam-combined are incident on the third polarizing beam-combining prism 11 after passing through the action of the third half-wave plate 12 , and are polarized and beam-combined with the laser beam emitted from the fourth laser 2 .

Each laser beam emitted from the laser 2 is subjected to phase modulation by a phase modulator 9 before being polarized and beam-combined.

In another specific embodiment, the number of slave lasers used for polarization beam combining can also be two or 5, 6 or more, and the beam combining principle and beam combining process are the same as those in the above specific embodiment , which will not be repeated here.

The semiconductor laser light source based on coherent polarization synthesis technology of the present invention combines coherent synthesis and polarization synthesis technology, and makes multiple single transverse mode semiconductor lasers meet the coherence condition through master-slave injection phase locking, and uses active phase modulation to control each channel The phase of the beam is controlled, and the coherent combination of multiple beams is realized by the method of polarization beam combining, and a coherent light source with high power and narrow linewidth can be obtained. This technology has no special structural requirements for the laser itself, and theoretically can realize the coherent combination of countless units, which is a very promising coherent combination technology.

In the semiconductor laser light source based on the coherent polarization synthesis technology of the present invention, the number of lasers can be determined according to the total power of the laser and the power of a single laser; ordinary polarization synthesis can only synthesize two lasers, and the present invention passes the phase of the laser Modulation can expand the number of combined beam lasers to an infinite number, which is very flexible.

Apparently, the above-mentioned embodiments are only examples for clear description, rather than limiting the implementation. For those of ordinary skill in the art, on the basis of the above description, other changes or changes in different forms can also be made. It is not necessary and impossible to exhaustively list all the implementation manners here. And the obvious changes or changes derived therefrom are still within the scope of protection of the present invention.

Claims (9)

1. based on the semiconductor laser light resource of cross polarization synthetic technology, it is characterized in that, comprising:

Main laser (1) and a plurality of from laser (2), seed light that described main laser (1) sends are divided into multichannel after through Amici prism (5), inject respectively a plurality of from laser (2) to realize phase locking from laser (2); The laser that each is launched from laser (2), that all launch from laser (2) with another one or synthetic through polarization, through the laser of half-wave plate (12) effect, it is synthetic to carry out polarization in polarization beam cementing prism (11);

The synthetic light beam that photodetector (10), described photodetector (10) are used for to polarization after synthetic is monitored in real time, signal can be passed to phase control module (8); Described phase control module (8) demodulates the phase error of two-beam, and control signal fed back to phase-modulator (9) thus each is carried out phase modulated from the light beam that laser (2) sends, the phase difference that participates in the synthetic two-way light beam of polarization is controlled at the integral multiple of π and remains linearly polarized light, close bundle thereby continue to carry out polarization, realize that cross polarization is synthetic with next road light beam.

2. semiconductor laser light resource according to claim 1 is characterized in that, all master and slave lasers are all fixing at grade.

3. semiconductor laser light resource according to claim 1 is characterized in that, also is separately installed with before the master and slave laser to be used for the collimating mirror (3) that reduces laser divergence angle, collimate.

4. semiconductor laser light resource according to claim 1, it is characterized in that, the seed light that described main laser (1) sends is injected a plurality of from laser (2) by the effect of completely reflecting mirror (6) and reflector plate (7) after being divided into multichannel through Amici prism (5); Described completely reflecting mirror (6) is a reflectivity near 100% reflector plate or reflecting prism.

5. semiconductor laser light resource according to claim 1, it is characterized in that, the seed light that described main laser (1) sends is injected a plurality of from laser (2) by the effect of completely reflecting mirror (6) and reflector plate (7) after being divided into multichannel through Amici prism (5); Described reflector plate (7) is for having the parallel flat of certain reflectivity, reflectance value from 1% to 50%.

6. semiconductor laser light resource according to claim 1 is characterized in that, described front facet from laser (2) is coated with reflectivity at the anti-reflection film more than 99%, has high injection rate to guarantee seed light.

7. semiconductor laser light resource according to claim 1 is characterized in that, employed phase control module (8) comprises phase-control circuit, lock-in amplifier, signal generator.

8. semiconductor laser light resource according to claim 1 is characterized in that, described phase-modulator (9) is lithium niobate (LiNbO ₃) phase-modulator.

9. according to the semiconductor laser light resource described in any one of the claim 1-8, it is characterized in that described a plurality of quantity from laser (2) are 4.

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