Laser wavelength locking and linewidth compression system

Abstract

The present invention discloses a laser wavelength locking and linewidth compression system, comprising: a plurality of lasers, each laser having a plurality of light sources; a plurality of first optical fibers, corresponding to the plurality of lasers one by one, one end of the first optical fiber being connected to the laser; an optical fiber combiner, the other ends of the plurality of first optical fibers being connected to the optical fiber combiner; a second optical fiber, one end of the second optical fiber being connected to the optical fiber combiner; a collimating element, the collimating element being connected to the other end of the second optical fiber; and a diffractive optical element, at least part of the diffractive optical element being arranged opposite to the light-emitting side of the collimating element. The optical fiber has a spectral homogenizing and mixing effect on the light beam it transmits, and the laser emitted by any light source will be uniformly fed back to all light sources to achieve mutual injection locking, ensuring that each light source outputs with a completely consistent central wavelength and linewidth.

Description

Technical Field

[0001] The invention relates to the field of laser technology, and in particular to a laser wavelength locking and line width compression system. Background Art

[0002] High-power wavelength-locked narrow-linewidth semiconductor lasers have a wide range of important applications: In the industrial field, for the efficient and stable pumping needs of high-power ytterbium-doped fiber lasers, it is usually necessary to wavelength-lock the 976nm semiconductor pump source, significantly reducing the drift of its central wavelength due to changes in ambient temperature or injection current, while compressing the spectral width from the unlocked 3-5nm (FWHM) to less than 1nm, effectively improving the pumping efficiency; in the medical field, based on hyperpolarized gas ( 3 He or 129 The lung magnetic resonance imaging technology of Xe, etc. can overcome the defects of traditional chest X-ray, CT or MRI technology in lung imaging, and provide an effective way for the early diagnosis of major lung diseases; and to realize the hyperpolarization process of the above-mentioned gas, it is necessary to apply a narrow-linewidth semiconductor pump source of hundreds of watts to control its central wavelength accuracy within ±0.1nm and the spectral linewidth within 0.2nm; in the field of national defense, semiconductor-pumped alkali metal vapor lasers are high-energy laser light sources with great potential. They use semiconductor lasers to pump alkali metal vapor to achieve high-energy laser output and use gas flow to dissipate heat efficiently; since alkali metal atoms have a fixed and extremely narrow absorption spectrum, the semiconductor pump source is required to meet the high-power output while its central wavelength must be strictly locked to the absorption spectrum of alkali metal atoms (potassium 766.7nm, rubidium 780.2nm, cesium 852.4nm), and the spectral width is required to be controlled within 0.1nm, which also poses new challenges to the traditional semiconductor laser wavelength locking and linewidth compression technology.

[0003] In terms of packaging form, high-power semiconductor lasers currently mainly use two methods: free-space output based on bar arrays and fiber-coupled output based on single-light source beam combination. The latter has more advantages in terms of thermal management, beam uniformity and reliability, and the fiber-coupled output method is more convenient and friendly in various applications because of the flexible transmission characteristics of optical fibers. At present, the wavelength locking and linewidth compression of fiber-coupled semiconductor lasers are mainly achieved through the external cavity method based on volume Bragg gratings. Other diffractive optical elements such as surface gratings and standard tools are usually used for precise spectral control of low-power semiconductor light sources within the watt level. Take the more mature 976nm wavelength-locked semiconductor laser in industry as an example: usually a 976nm fiber-coupled semiconductor laser module containing 19 light sources, the output beams of each light source are densely arranged in space by step beam combination; there are usually two ways to construct a volume Bragg grating external cavity: one is to place a volume Bragg grating at the front end of each light source to form an external cavity, and the other is to share a larger volume Bragg grating to form an external cavity for the beams after step beam combination. Both methods have been proven to be effective. After the external cavity structure is formed, according to the grating parameter characteristics of the volume Bragg grating, it will selectively feed back a portion of the wavelength-locked, narrow-linewidth spectrum to the light source, and couple with the light field of the active region of the light source, and strengthen the part of the spectral component of the light source that is the same as the feedback spectrum, and suppress the part that is different from the feedback spectrum, thereby achieving wavelength locking and linewidth narrowing of the output spectrum of each light source and the entire fiber-coupled semiconductor laser module. The wavelength-locked beam output through the external cavity is coupled to the energy transmission fiber after passing through the focusing optical system. Usually, the output power of a 976nm fiber-coupled semiconductor laser module containing 19 light sources is in the hundreds of watts. Further use of a 19×1 fiber combiner can achieve kilowatt-level power output.

[0004] The above high-power fiber-coupled semiconductor laser external cavity solution is feasible and effective for weak spectral narrowing (spectral width of 0.5-1nm), but it is insufficient for more stringent spectral requirements. Taking alkali metal laser pumping as an example, it is required that under high pump power conditions, the central wavelength and the atomic absorption line are strictly aligned (taking cesium as an example, 852.4±0.05nm), and the spectral line width is controlled within 0.1nm. To meet the above requirements, for a hundred-watt fiber-coupled semiconductor laser module, a volume Bragg grating can be placed at the front end of each light source. However, due to the discreteness of the diffraction center wavelength of the volume Bragg grating, the use of a large number of volume Bragg gratings will lead to the deviation of the center wavelength and the broadening of the total output spectrum. One of the technical means to solve this problem is to actively control the temperature of the grating to make the center wavelength consistent, but the use of a large number of gratings also brings difficulties to active wavelength control; another solution is to first perform step-by-step beam combining on each light source of this hundred-watt fiber-coupled semiconductor laser module, and the combined light beams share a large volume Bragg grating to form an external cavity. This method will cause the laser fed back by a grating to be unable to be fed back to all light sources evenly and efficiently, resulting in poor locking effect of some light sources, resulting in the deterioration of the overall spectrum. Summary of the invention

[0005] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, the present invention proposes a laser wavelength locking and linewidth compression system, which can make the feedback light fed back to all light sources more uniform, ensuring that each light source outputs with completely consistent central wavelength and linewidth.

[0006] According to some embodiments of the present invention, the laser wavelength locking and linewidth compression system comprises: a plurality of lasers, each of which has a plurality of light sources; a plurality of first optical fibers, corresponding to the plurality of lasers one by one, one end of the first optical fibers being connected to the lasers; an optical fiber combiner, the other ends of the plurality of first optical fibers being connected to the optical fiber combiner; a second optical fiber, one end of the second optical fiber being connected to the optical fiber combiner; a collimating element, the collimating element being connected to the other end of the second optical fiber; and a diffractive optical element, at least a portion of the diffractive optical element being arranged opposite to a light emitting side of the collimating element;

[0007] Among them, the light output by each light source of the plurality of lasers is transmitted to the fiber combiner through the plurality of first optical fibers respectively, enters the second optical fiber after passing through the fiber combiner, and is output through the second optical fiber; the light beam output by the second optical fiber is transmitted to the collimating element and collimated by the collimating element, the light beam collimated by the collimating element enters the diffractive optical element, and a part of it is intercepted by the diffractive optical element as feedback light; the feedback light is fed back into the second optical fiber through the collimating element, and is reversely transmitted to the fiber combiner through the second optical fiber, and then transmitted to each of the first optical fibers and each of the lasers in equal proportion, and the feedback light transmitted to each laser is then incident back to each light source of each laser in equal proportion.

[0008] The laser wavelength locking and linewidth compression system according to the embodiment of the present invention has at least the following beneficial effects:

[0009] 1. The optical fiber has a spectral homogenization and mixing effect on the light beam it transmits. The laser emitted by any light source will be uniformly fed back to all light sources to achieve mutual injection locking, ensuring that each light source outputs with completely consistent central wavelength and line width. It is understandable that the light directly emitted by different light sources has slight differences (central wavelength and output line width, etc.). This part of the light is mixed and homogenized after being coupled into the optical fiber and transmitted through the same optical fiber, that is, all light sources ultimately receive evenly mixed light, that is, other light sources have achieved injection locking for this light source, rather than only receiving the light emitted by itself, thus achieving mutual injection locking and improving the spectral consistency of different light sources.

[0010] 2. Only a single diffractive optical element is needed to lock the wavelength and compress the line width of several lasers. It has low cost, simple structure and good power scalability. The tuning of the central wavelength can be achieved by changing the parameters of the diffractive optical element.

[0011] According to some embodiments of the present invention, the wavelength of the laser emitted by the laser is any wavelength between 600 nm and 2500 nm.

[0012] According to some embodiments of the present invention, the wavelength of the laser emitted by the laser is 795 nm or 976 nm.

[0013] According to some embodiments of the present invention, the diffractive optical element is a volume Bragg grating.

[0014] According to some embodiments of the present invention, the diffractive optical element is a plane diffraction grating.

[0015] According to some embodiments of the present invention, the diffractive optical element is a narrow-band mirror.

[0016] According to some embodiments of the present invention, the laser is a semiconductor laser.

[0017] According to some embodiments of the present invention, the front end surface of the semiconductor chip of the light source of the semiconductor laser is coated with an anti-reflection film.

[0018] According to some embodiments of the present invention, the laser is a fiber laser.

[0019] According to some embodiments of the present invention, the laser is a solid laser or a gas laser.

[0020] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The present invention will be further described below with reference to the accompanying drawings and embodiments, wherein:

[0022] Figure 1 This is a schematic diagram of the structure of a laser wavelength locking and linewidth compression system according to Embodiment 1 of the present invention;

[0023] Figure 2 Schematic diagram of the structure of a laser wavelength locking and linewidth compression system according to the second embodiment of the present invention.

[0024] Figure Number:

[0025] 100, laser; 200, first optical fiber; 300, optical fiber combiner; 400, second optical fiber; 500, collimating element; 600, diffractive optical element. DETAILED DESCRIPTION

[0026] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be understood as limiting the present invention.

[0027] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "axial", "radial", "circumferential" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. In addition, features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0028] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0029] like Figure 1 As shown, a laser wavelength locking and linewidth compression system provided by the present invention includes multiple lasers 100, multiple first optical fibers 200, an optical fiber combiner 300, a second optical fiber 400, a collimating element 500 and a single diffractive optical element 600.

[0030] The laser 100 has multiple light sources; multiple first optical fibers 200 correspond one-to-one to the multiple lasers 100, and one end of the first optical fiber 200 is connected to the laser 100; the other ends of the multiple first optical fibers 200 are all connected to the fiber combiner 300; one end of the second optical fiber 400 is connected to the fiber combiner 300; the collimating element 500 is connected to the other end of the second optical fiber 400; at least a portion of the diffractive optical element 600 is arranged opposite to the light emitting side of the collimating element 500.

[0031] It should be noted that the number of first optical fibers 200 is the same as the number of lasers 100 , and multiple first optical fibers 200 are connected to multiple lasers 100 one by one, and the ends of multiple first optical fibers 200 away from the lasers 100 are connected to the fiber combiner 300 together.

[0032] It should be further explained that the light-exiting side of the collimating element 500 refers to the side from which light enters the collimating element 500 through the second optical fiber 400 and is emitted from the collimating element 500 .

[0033] Among them, the light output by each light source of the multiple lasers 100 is transmitted to the fiber combiner 300 through the multiple first optical fibers 200, enters the second optical fiber 400 after passing through the fiber combiner 300, and is output through the second optical fiber 400; the light beam output by the second optical fiber 400 is transmitted to the collimating element 500 and collimated by the collimating element 500, the light beam collimated by the collimating element 500 enters the diffractive optical element 600, and a part of it is intercepted by the diffractive optical element 600 as feedback light; the feedback light is fed back into the second optical fiber 400 through the collimating element 500, and is reversely transmitted to the fiber combiner 300 through the second optical fiber 400, and then transmitted to each first optical fiber 200 and each laser 100 in equal proportion, and the feedback light transmitted to each laser 100 is then incident back to each light source of each laser 100 in equal proportion.

[0034] Specifically, the light output by the laser 100 having multiple light sources is transmitted through the first optical fiber 200, and the power is superimposed by the optical fiber combiner 300, and then coupled into the second optical fiber 400; for the light beam output by the second optical fiber 400, it is first collimated by the collimating element 500, and then a part of the collimated output light beam is intercepted by the diffractive optical element 600 having a narrow-band reflection characteristic for the required wavelength as feedback light, and the feedback light is fed back into the second optical fiber 400 through the collimating element 500, and is reversely transmitted to the optical fiber combiner 300 through the second optical fiber 400; the light beam fed back to the optical fiber combiner 300 will be transmitted to each first optical fiber 200 and each laser 100 in equal proportion, and then further incident back to each light source of each laser 100 in equal proportion, and an external resonant cavity is formed, thereby achieving wavelength locking and line width compression of the light emitted by all light sources.

[0035] It should be noted that the light beam intercepted by the diffractive optical element 600 is related to the diffractive optical element 600, and is the light obtained after the diffractive optical element 600 selects the frequency. The characteristics of this part of light are stable central wavelength (corresponding to the selected frequency wavelength of the diffractive optical element 600) and narrow spectral line width, and can be returned to the external resonant cavity to control the mode competition. Among them, the part of the spectral component of the light source that is the same as the feedback spectrum gains an advantage in the competition, and the part that is different from the feedback spectrum is suppressed, and finally the wavelength locking and line width narrowing of each light source and the entire laser 100 are achieved.

[0036] The present invention adopts a technical solution of first superimposing the power of the light beams output by multiple lasers 100 and then using a single diffractive optical element 600 to form an external resonant cavity, which has the following outstanding advantages:

[0037] 1. The optical fiber has a spectral homogenization and mixing effect on the light beam it transmits. The laser emitted by any light source will be uniformly fed back to all light sources to achieve mutual injection locking, ensuring that each light source outputs with completely consistent central wavelength and line width. It is understandable that the light directly emitted by different light sources has slight differences (central wavelength and output line width, etc.). This part of the light is mixed and homogenized after being coupled into the optical fiber and transmitted through the same optical fiber, that is, all light sources ultimately receive evenly mixed light, that is, other light sources have achieved injection locking for this light source, rather than only receiving the light emitted by itself, thus achieving mutual injection locking and improving the spectral consistency of different light sources.

[0038] 2. Only a single diffractive optical element 600 is used to lock the wavelengths and compress the line width of several lasers 100, which has low cost, simple structure and good power scalability. The tuning of the central wavelength can be achieved by changing the parameters of the diffractive optical element 600.

[0039] Embodiment 1:

[0040] Figure 1 A laser wavelength locking and linewidth compression system is provided in Example 1, which includes three lasers 100, three first optical fibers 200, a fiber combiner 300, a second optical fiber 400, a collimating element 500 and a single diffractive optical element 600.

[0041] Among them, the laser 100 is a 795nm fiber-coupled semiconductor laser, including 9 light sources, each of which is densely arranged in a linear array through a step-by-step beam combining method. The output power of each light source is about 9 watts, and the output power of a single laser 100 is about 81 watts. The central wavelength of the free-running output spectrum of the light source is 795±2nm, and the spectrum width is 3-5nm; the front end surface of the semiconductor chip of the light source is coated with a 795±2nm anti-reflection film with a reflectivity within 0.1%, which is used to suppress the free spectrum output and achieve a better external resonant cavity spectrum regulation effect. The core of the first optical fiber 200 is 105um and the numerical aperture is 0.22; the optical fiber combiner 300 is a 3×1 optical fiber combiner 300; the core of the second optical fiber 400 is 125um and the numerical aperture is 0.46; the collimating element 500 is a lens; the diffractive optical element 600 is a volume Bragg grating, and the diffraction center wavelength of the volume Bragg grating is selected to be 795nm, which is aligned with the D1 absorption line of the rubidium atom, the diffraction bandwidth is 0.05nm, the diffraction efficiency is 15%, and the geometric cross-sectional area can cover the light beam collimated by the collimating element 500.

[0042] The laser light emitted by the laser 100 is efficiently coupled to the first optical fiber 200 for transmission, and power synthesis is achieved through the optical fiber combiner 300 and output through the second optical fiber 400. The light beam output by the second optical fiber 400 is expanded and collimated by the collimating element 500. The collimated light beam is incident on the diffractive optical element 600, 15% of the light beam incident on the diffractive optical element 600 is reflected, and the reflected light beam enters the collimating element 500 in the reverse direction and is recoupled to the second optical fiber 400, and is finally fed back to a total of 27 light sources of the three lasers 100. Due to the mixing effect of the second optical fiber 400 on the light beam spectrum, each light source will receive the feedback light of all the light sources, thereby forming an external resonant cavity with a mutual injection locking effect. Under the action of the external resonant cavity, the resonant center wavelength of each light source is locked to the diffraction wavelength of the diffractive optical element 600, and the spectrum width is equivalent to the diffraction bandwidth of the diffractive optical element 600. It should be noted that, of the light beam incident on the diffractive optical element 600, 15% is reflected, and 85% is output with a locked spectrum. Considering the heating effect of the incident laser of a hundred-watt level on the diffractive optical element 600, which may cause the diffraction wavelength to drift (about 8-10pm / ℃), the output center wavelength of the diffractive optical element 600 can be precisely aligned with the D1 line absorption spectrum of the rubidium atom by precise temperature control tuning; the laser 100 that has been wavelength locked and line width compressed generally has an external resonant cavity efficiency of 90%. Considering the losses such as coupling and fiber fusion, the total output power is about 200 watts and the spectrum width is about 0.05nm, which can be applied to rubidium atom polarization pumping and transmitted to the 3 He or 129 Xe and others are used in lung magnetic resonance imaging.

[0043] Embodiment 2

[0044] Figure 2 A laser wavelength locking and linewidth compression system is provided for the second embodiment, which includes 19 lasers 100, 19 first optical fibers 200, an optical fiber combiner 300, a second optical fiber 400, a collimating element 500 and a single diffractive optical element 600.

[0045] Among them, the laser 100 is a 976nm fiber-coupled semiconductor laser, including 18 light sources, each of which is densely arranged in a linear array through step and polarization beam combining. The output power of each light source is about 10 watts, and the output power of a single laser 100 is about 180 watts. The central wavelength of the free-running output spectrum of the light source is 976±2nm, and the spectrum width is 3-5nm; the front end surface of the semiconductor chip of the light source is coated with a 976±2nm anti-reflection film with a reflectivity within 0.5%, which is used to suppress the free spectrum output and achieve a better external resonant cavity spectrum regulation effect. The core of the first optical fiber 200 is 105um and the numerical aperture is 0.22; the optical fiber combiner 300 is a 19×1 optical fiber combiner 300; the core of the second optical fiber 400 is 400um and the numerical aperture is 0.46; the collimating element 500 is a lens; the diffractive optical element 600 is a volume Bragg grating, the diffraction center wavelength of the volume Bragg grating is selected to be 976nm, the diffraction bandwidth is 0.5nm, the diffraction efficiency is 99%, and the geometric cross-sectional area can cover the light beam collimated by the collimating element 500.

[0046] The laser emitted by the laser 100 is efficiently coupled to the first optical fiber 200 for transmission, and power synthesis is achieved through the optical fiber combiner 300 and output to the second optical fiber 400; the light beam output by the second optical fiber 400 is expanded and collimated by the collimating element 500; since the kilowatt-level power laser will cause the diffractive optical element 600 to be overloaded, it cannot be fully loaded. An area of ​​nearly 4% is selected in the cross section of the collimated output beam, and this part of the laser (power is about 180 watts×19 channels×4%) is incident on the diffractive optical element 600. The light beam incident on the diffractive optical element 600 is totally reflected, and the reflected light beam enters the collimating element 500 in the reverse direction and is recoupled to the second optical fiber 400, and finally fed back to a total of 342 light sources of 19 lasers 100. Due to the mixing effect of the second optical fiber 400 on the light beam, each light source will receive the feedback light of all other light sources, forming a mutual injection locking effect. External resonant cavity; under the action of the external resonant cavity, the resonant center wavelength of each light source is locked to the diffraction wavelength of the diffractive optical element 600, and the spectrum width is equivalent to the diffraction bandwidth of the diffractive optical element 600. Considering the heating effect of the kilowatt-level incident laser on the diffractive optical element 600, which may cause the diffraction wavelength to drift (about 8-10pm / ℃), the wavelength can be tuned by precisely temperature-controlling the diffractive optical element 600; the remaining part of the light beam that is not incident on the diffractive optical element 600 outputs laser light with a locked spectrum, and the efficiency of the resonant external cavity is equivalent to the ratio of the light beam transmission area, which is about 96%. Considering the losses such as coupling and fiber fusion, the total output power is about 3 kilowatts. Due to the wavelength locking effect of the resonant external cavity, the center wavelength drift coefficient of the above-mentioned light source caused by temperature and current disturbances is reduced by nearly an order of magnitude compared with the free operation state, and can be used for the subsequent efficient and stable pumping of the ytterbium-doped high-energy laser 100.

[0047] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0048] Although the embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the claims and their equivalents.

Claims

1. A laser wavelength locking and linewidth compression system, characterized in that: include: a plurality of lasers, each of said lasers having a plurality of light emitting sources; A plurality of first optical fibers, corresponding one to one with a plurality of lasers, one end of the first optical fiber being connected to the laser; an optical fiber combiner, to which the other ends of the plurality of first optical fibers are connected; A second optical fiber, one end of which is connected to the optical fiber combiner; a collimating element connected to the other end of the second optical fiber; a diffractive optical element, at least a portion of which is arranged opposite to the light-emitting side of the collimating element; The light outputted by each light source of the plurality of lasers is transmitted to the fiber combiner through the plurality of first optical fibers respectively, enters the second optical fiber after passing through the fiber combiner, and is outputted through the second optical fiber; the light beam outputted by the second optical fiber is transmitted to the collimating element and collimated by the collimating element, the light beam collimated by the collimating element enters the diffractive optical element, and at least a part of the light beam is intercepted by the diffractive optical element as feedback light; The feedback light is fed back into the second optical fiber through the collimating element, and is transmitted back to the optical fiber combiner through the second optical fiber, and then transmitted to each of the first optical fibers and each of the lasers in equal proportion. The feedback light transmitted to each laser is then incident back into each light source of each laser in equal proportion.

2. The laser wavelength locking and linewidth compression system according to claim 1, characterized in that: The wavelength of the laser emitted by the laser is any wavelength between 600nm and 2500nm.

3. The laser wavelength locking and linewidth compression system according to claim 1, characterized in that: The wavelength of the laser emitted by the laser is 795nm or 976nm.

4. The laser wavelength locking and linewidth compression system according to claim 1, characterized in that: The diffractive optical element is a volume Bragg grating.

5. The laser wavelength locking and linewidth compression system according to claim 1, characterized in that: The diffractive optical element is a plane diffraction grating.

6. The laser wavelength locking and linewidth compression system according to claim 1, characterized in that: The diffractive optical element is a narrow-band reflector.

7. The laser wavelength locking and linewidth compression system according to claim 1, characterized in that: The laser is a semiconductor laser.

8. The laser wavelength locking and linewidth compression system according to claim 7, characterized in that: The front end surface of the semiconductor chip of the light source of the semiconductor laser is plated with an anti-reflection film.

9. The laser wavelength locking and linewidth compression system according to claim 1, characterized in that: The laser is a fiber laser.

10. The laser wavelength locking and linewidth compression system according to claim 1, characterized in that: The laser is a solid laser or a gas laser.

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