Tunable Ultra-Narrow Linewidth Laser

Abstract

The present invention provides a tunable ultra-narrow linewidth laser, including a laser generation gain unit, a distributed scattering feedback unit, a first light collimating lens, and a second light collimating lens. The first output end and the second output end of the laser generation gain unit are correspondingly provided with a first film and a second film, and both the first film and the second film have transmission and reflection characteristics. The first output end of the laser generation gain unit is connected to the distributed scattering feedback unit through the first film and the first light collimating lens in sequence, and the second output end is connected to the second light collimating lens through the second film, and the other end of the second light collimating lens is connected to the tunable filter unit. In the present invention, the optical signal generated by the laser generation gain unit is transmitted based on the above path, and the deep compression of the laser linewidth in the wavelength tuning process can be obtained to meet the demand for compression of the laser linewidth of different wavelengths; the present invention can obtain ultra-narrow linewidth output with a high side mode suppression ratio for lasers of different tuning wavelengths.

Description

Technical Field

[0001] The invention belongs to the technical field of tunable lasers, and in particular relates to a tunable ultra-narrow linewidth laser. Background Art

[0002] Ultra-narrow linewidth lasers with tunable output wavelengths not only have flexible wavelength selectivity and a wide range of wavelength tunability, but also have ultra-long coherence length and extremely low phase noise. Therefore, they have very important application prospects in many emerging fields such as coherent detection, optical resolution spectroscopy, precision sensing and biomedicine. So far, the use of short cavity structure and saturated absorber methods is a common method to achieve wavelength tunability while ensuring that the laser operates in a single longitudinal mode. However, these traditional methods only achieve laser mode selection and cannot achieve further compression of the laser linewidth on this basis. Therefore, how to achieve deep compression of the laser linewidth while achieving continuous tunability of the laser wavelength is a difficult problem currently faced by this field. Summary of the invention

[0003] The present invention provides a tunable ultra-narrow linewidth laser to solve the problem in the field of tunable lasers that a traditional method is used to achieve continuous wavelength regulation while failing to achieve stable ultra-narrow linewidth output, and overcomes the separation and bulkiness problems of traditional laser systems by connecting a compression element to a laser gain chip.

[0004] According to one aspect of the present invention, a tunable ultra-narrow linewidth laser is provided, comprising a laser generating gain unit, a distributed scattering feedback unit, a first light collimating lens, a second light collimating lens and a tunable filter element, wherein the first output end and the second output end of the laser generating gain unit are respectively provided with a first film and a second film, and both the first film and the second film have transmission and reflection characteristics, the first output end of the laser generating gain unit is connected to the first end of the distributed scattering feedback unit through the first film and the first light collimating lens in sequence, and the second output end is connected to the tunable filter element through the second film and the second light collimating lens in sequence;

[0005] The laser generation gain unit is used to generate an initial optical signal with a wide spectrum and transmit the generated optical signal to the first film and the second film respectively; after receiving the optical signal, the first film transmits a part of the optical signal to the laser generation gain unit, and transmits the other part to the distributed scattering feedback unit through the first optical collimating lens; after receiving the optical signal, the second film transmits a part of the optical signal to the laser generation gain unit, and transmits the other part to the tunable filter element through the second optical collimating lens;

[0006] After receiving the optical signal, the tunable filter element performs wavelength selection and tuning on the optical signal to obtain an optical signal with a specific wavelength. A part of the optical signal with the specific wavelength is transmitted to the second film through the second optical collimating lens, and the other part is directly output. After receiving the optical signal, the first end of the distributed scattering feedback unit performs line width compression on the optical signal, and transmits the optical signal fed back after line width compression to the first film through the first optical collimating lens. After receiving the optical signal, the laser generation gain unit performs gain amplification on the optical signal, and transmits the gain-amplified optical signal to the first film and the second film respectively. When reaching a steady state, the optical signal with the specific wavelength is cyclically line width compressed by the distributed scattering feedback unit, and the obtained single longitudinal mode ultra-narrow line width optical signal is output from the other end of the tunable filter element.

[0007] In an optional implementation, the distributed scattering feedback unit also outputs the optical signal transmitted forward after line width compression through its second end.

[0008] According to another aspect of the present invention, a tunable ultra-narrow linewidth laser is provided, comprising a laser generating gain unit, a distributed scattering feedback unit, a first light collimating lens, a second light collimating lens and a tunable filter element, wherein the first output end and the second output end of the laser generating gain unit are respectively provided with a first film and a second film, the first film has transmission and reflection characteristics, and the second film has reflection characteristics, the first output end of the laser generating gain unit is connected to the first end of the distributed scattering feedback unit through the first film and the first light collimating lens in sequence, the second output end is connected to the second film, and the second end of the distributed scattering feedback unit is connected to the tunable filter element;

[0009] The laser generation gain unit is used to generate an initial optical signal with a wide spectrum and transmit the generated optical signal to the first film and the second film respectively; after receiving the optical signal, the first film transmits a part of the optical signal to the laser generation gain unit, and transmits the other part to the first end of the distributed scattering feedback unit through the first optical collimating lens; after receiving the optical signal, the second film transmits the optical signal to the laser generation gain unit; after receiving the optical signal, the laser generation gain unit performs gain amplification on the optical signal, and transmits the gain-amplified optical signal to the first film and the second film again respectively;

[0010] After receiving the optical signal, the first end of the distributed scattering feedback unit performs line width compression on the optical signal, and transmits the optical signal fed back after line width compression to the first film through the first optical collimating lens, and transmits the optical signal transmitted forward after line width compression to the tunable filter element; after receiving the optical signal, the tunable filter element performs wavelength selection and tuning on the optical signal to obtain an optical signal with a specific wavelength, and a part of the optical signal with a specific wavelength is transmitted to the second end of the distributed scattering feedback unit, and the other part is directly output;

[0011] After receiving the optical signal of the specific wavelength, the second end of the distributed scattering feedback unit compresses the line width of the optical signal, and transmits the optical signal transmitted forward after the line width compression to the first film through the first optical collimating lens, and transmits the optical signal fed back backward after the line width compression to the tunable filter element; when reaching a steady state, the optical signal of the specific wavelength is cyclically line-width compressed by the distributed scattering feedback unit, and the obtained single longitudinal mode ultra-narrow line width optical signal is output from the tunable filter element.

[0012] In an optional implementation, the second film also has a transmission property, and the second film is also connected to a second light collimating lens. After receiving the light signal, the second film transmits a part of the light signal to the laser generation gain unit, and outputs the other part through the second light collimating lens.

[0013] In another optional implementation, an optical isolator is further included, and the tunable filter element is connected to the optical isolator to output the obtained single longitudinal mode ultra-narrow linewidth optical signal through the optical isolator.

[0014] In another optional implementation, the distributed scattering feedback unit includes a special optical fiber with a high scattering coefficient, a waveguide structure made of a special gas material, or a special scattering waveguide engraved on a substrate.

[0015] In another optional implementation, the distributed scattering feedback unit is used to achieve self-matching of the laser wavelength and the effective distributed scattering cavity; the distributed scattering feedback unit is all distributed scattering mechanisms represented by Rayleigh scattering, and cyclic compression adjustment of the optical signal line width is achieved by adjusting the scattering coefficient and signal feedback ratio of the distributed scattering feedback unit.

[0016] In another optional implementation, the laser generation gain unit includes a gain medium, which generates an initial light signal with a wide spectrum under electrical excitation and transmits the generated light signal to the first film and the second film respectively. After receiving the light signal, the light signal is gain amplified during the laser resonance process, and the gain-amplified light signal is again transmitted to the first film and the second film respectively.

[0017] In another optional implementation, at least the laser generation gain unit, the distributed scattering feedback unit, the first light collimating lens, the second light collimating lens and the tunable filtering unit are integrated on a substrate.

[0018] In another optional implementation, the laser generating gain unit can cover any wavelength band of laser gain, and the compression mechanism is not wavelength selective and is applicable to deep compression of any wavelength band and any type of laser line width.

[0019] The beneficial effects of the present invention are:

[0020] 1. In the present invention, a first film and a second film are correspondingly arranged (for example, coated) at two output ends of a laser generating gain unit, and the first output end of the laser generating gain unit is connected to a distributed scattering feedback unit through the first film and a first light collimating lens in sequence, and the second output end of the laser generating gain unit is connected to a tunable filter element through the second film and a second light collimating lens in sequence, so that both the first film and the second film have transmission and reflection characteristics, the laser generating gain unit performs cyclic gain amplification on the optical signal, and the distributed scattering feedback unit performs cyclic line width compression on the optical signal. The optical signal generated by the laser generating gain unit is transmitted based on the above path, and optical signal outputs of more wavelength types can be obtained to meet different wavelength line width compression selection requirements; by configuring the laser generating gain unit, the distributed scattering feedback unit, the first film and the second film The positional relationship between the films is designed so that the optical signal after line width compression can be fully amplified before being output, thereby greatly reducing the energy consumption of the device; the present invention is also provided with a tunable filter element, and before the optical signal is cyclically compressed, the optical signal of a specific wavelength is first selected, and then the selected optical signal of a specific wavelength is returned to the second optical collimating lens, so that the distributed scattering feedback unit only performs line width compression on the optical signal of the specific wavelength, and the laser generation gain unit only performs gain amplification on the optical signal of the specific wavelength, thereby improving the output efficiency of the optical signal of the specific wavelength and further reducing the energy consumption of the laser; the present invention realizes deep compression of the laser line width during the wavelength tuning process through cyclic compression of the distributed scattering feedback unit, and obtains an ultra-narrow line width optical signal with relatively high side mode suppression, which is simpler than the conventional design structure;

[0021] 2. The present invention can select and tune the wavelength of the output optical signal by setting a tunable filter unit to meet the different needs of users;

[0022] 3. The invention realizes self-matching of laser wavelength and effective distributed feedback cavity through the distributed feedback characteristics of distributed scattering feedback unit;

[0023] 4. The present invention transmits the optical signal of the corresponding wavelength after wavelength selection and tuning to the laser generation gain unit, so that the laser generation gain unit starts to generate only the optical signal of the corresponding wavelength after receiving the optical signal of the corresponding wavelength, which can further reduce the energy consumption of the device and improve the output efficiency of the target wavelength optical signal;

[0024] 5. The present invention can achieve integration and improve system stability by integrating various components on a substrate. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a schematic structural diagram of an embodiment of a tunable ultra-narrow linewidth laser of the present invention;

[0026] Figure 2 It is a schematic structural diagram of another embodiment of the tunable ultra-narrow linewidth laser of the present invention.

[0027] In the figure: a laser generating gain unit 1, a first collimating lens 2, a distributed scattering feedback unit 3, a second collimating lens 4, a tunable filtering unit 5, an optical isolator 6, a first film 100, a second film 101, and a gain medium 102. DETAILED DESCRIPTION

[0028] In order to enable those skilled in the art to better understand the technical solutions in the embodiments of the present invention and to make the above-mentioned purposes, features and advantages of the embodiments of the present invention more obvious and understandable, the technical solutions in the embodiments of the present invention are further described in detail below in conjunction with the accompanying drawings.

[0029] In the description of the present invention, unless otherwise specified and limited, it should be noted that the term "connection" should be understood in a broad sense. For example, it can be a mechanical connection or an electrical connection, or it can be the internal connection between two elements. It can be a direct connection or an indirect connection through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0030] See also Figure 1, is a schematic diagram of the structure of an embodiment of a tunable ultra-narrow linewidth laser of the present invention. The tunable ultra-narrow linewidth laser may include a laser generation gain unit 1, a distributed scattering feedback unit 3, a first light collimating lens 2, a second light collimating lens 4 and a tunable filter element 5. The first output end and the second output end of the laser generation gain unit 1 are correspondingly provided with a first film 100 and a second film 101. The first film 100 and the second film 101 both have transmission and reflection characteristics. The first output end of the laser generation gain unit 1 is connected to the first end of the distributed scattering feedback unit 3 through the first film 100 and the first light collimating lens 2 in sequence, and the second output end is connected to the tunable filter element 5 through the second film 101 and the second light collimating lens 4 in sequence; the laser generation gain unit 1 is used to generate an initial optical signal with a wide spectrum and transmit the generated optical signal to the first film 100 and the second film 101 respectively. After receiving the optical signal, the first film 100 transmits a part of it to the laser generation gain unit 1, and transmits the other part to the distributed scattering feedback unit 3 through the first light collimating lens 2; the second film 1 01 after receiving the optical signal, transmits a part of it to the laser generating gain unit 1, and transmits the other part to the tunable filter element 5 through the second optical collimating lens 4; after receiving the optical signal, the tunable filter element 5 performs wavelength selection and tuning on the optical signal to obtain an optical signal with a specific wavelength, a part of the optical signal with a specific wavelength is transmitted to the second film 101 through the second optical collimating lens 4, and the other part is directly output; after receiving the optical signal, the first end of the distributed scattering feedback unit 3 performs line width compression on the optical signal, and transmits the optical signal fed back after line width compression to the first film 100 through the first optical collimating lens 2; after receiving the optical signal, the laser generating gain unit 1 performs gain amplification on the optical signal, and transmits the gain amplified optical signal to the first film 100 and the second film 101 respectively; when reaching a steady state, the optical signal with a specific wavelength is cyclically line width compressed by the distributed scattering feedback unit 3, and the obtained single longitudinal mode ultra-narrow line width optical signal is output from the tunable filter element 5.

[0031] It can be seen from the above embodiments that the present invention has a first film and a second film correspondingly arranged (for example, coated) at the two output ends of the laser generation gain unit, and the first output end of the laser generation gain unit is connected to the distributed scattering feedback unit through the first film and the first light collimating lens in sequence, and the second output end of the laser generation gain unit is connected to the tunable filter element through the second film and the second light collimating lens in sequence, so that the first film and the second film both have transmission and reflection characteristics, the laser generation gain unit performs cyclic gain amplification on the optical signal, and the distributed scattering feedback unit performs cyclic line width compression on the optical signal. The optical signal generated by the laser generation gain unit is transmitted based on the above path, and optical signals of different tunable wavelengths can be realized. The line width of the signal is compressed to meet the needs of line width compression of different wavelengths; the tunable filter element in the present invention first selects the optical signal of a specific wavelength before the optical signal is cyclically compressed, and then returns the selected optical signal of a specific wavelength to the second optical collimating lens, so that the distributed scattering feedback unit only performs line width compression on the optical signal of the specific wavelength, and the laser generation gain unit only performs gain amplification on the optical signal of the specific wavelength; when the tunable filter element selects another laser wavelength, when the optical signal with this wavelength is transmitted based on the optical path, the distributed scattering feedback unit performs line width compression on the optical signal of this wavelength, thereby realizing the compression of the laser signal line width during the wavelength tuning process. The present invention realizes deep compression of laser line widths of different tuned wavelengths through cyclic compression of the distributed scattering feedback unit, and obtains ultra-narrow line width optical signals with relatively high side mode suppression, which is simpler than conventional design structures.

[0032] Since the structure of the laser of the present invention is simple, the present invention is particularly applicable in the process of realizing laser integration and chipization. In addition, after receiving the optical signal, the first end of the distributed scattering feedback unit 3 also outputs the optical signal transmitted forward after line width compression through its second end, thereby realizing double-end output.

[0033] See also Figure 2, is a schematic diagram of the structure of another embodiment of a tunable ultra-narrow linewidth laser of the present invention. The tunable ultra-narrow linewidth laser may include a laser generation gain unit 1, a distributed scattering feedback unit 3, a first light collimating lens 2, a second light collimating lens 4 and a tunable filter element 5. The first output end and the second output end of the laser generation gain unit 1 are correspondingly provided with a first film 100 and a second film 101. The first film 100 has transmission and reflection characteristics, and the second film 101 has reflection characteristics. The first output end of the laser generation gain unit 1 is connected to the first end of the distributed scattering feedback unit 3 through the first film 100 and the first light collimating lens 2 in sequence, and the second output end is connected to the second film 101. The second end of the distributed scattering feedback unit 3 is connected to the tunable Filter element 5; the laser generation gain unit 3 is used to generate an initial optical signal with a wide spectrum and transmit the generated optical signal to the first film 100 and the second film 101 respectively. After receiving the optical signal, the first film 100 transmits a part of it to the laser generation gain unit 1, and transmits the other part to the first end of the distributed scattering feedback unit 3 through the first optical collimating lens 2; after receiving the optical signal, the second film 101 transmits the optical signal to the laser generation gain unit 1; after receiving the optical signal, the laser generation gain unit 1 performs gain amplification on the optical signal, and transmits the gain-amplified optical signal to the first film 100 and the second film 101 respectively again.

[0034] After receiving the optical signal, the first end of the distributed scattering feedback unit 3 performs line width compression on the optical signal, and transmits the optical signal fed back after line width compression to the first film 100 through the first optical collimating lens 2, and transmits the optical signal transmitted forward after line width compression to the tunable filter element 5; after receiving the optical signal, the tunable filter element 5 performs wavelength selection and tuning on the optical signal to obtain an optical signal with a specific wavelength, a part of which is transmitted to the second end of the distributed scattering feedback unit 3, and the other part is directly output; after receiving the optical signal of the specific wavelength, the second end of the distributed scattering feedback unit 3 performs line width compression on the optical signal, and transmits the optical signal transmitted forward after line width compression to the first film 100 through the first optical collimating lens 2, and transmits the optical signal fed back after line width compression to the tunable filter element 5; when reaching a steady state, the optical signal of the specific wavelength is cyclically line width compressed by the distributed scattering feedback unit 3, and the obtained single longitudinal mode ultra-narrow line width optical signal is output from the tunable filter element 5.

[0035] Similarly, it can be seen from the above embodiments that the present invention provides a first film and a second film at two output ends of the laser generation gain unit, and connects the first output end of the laser generation gain unit to the distributed scattering feedback unit through the first film and the first light collimating lens in sequence, and connects the second output end of the laser generation gain unit to the second film, so that the first film has transmission and reflection characteristics, and the second film has reflection characteristics. The laser generation gain unit performs cyclic gain amplification on the optical signal, the distributed scattering feedback unit performs cyclic line width compression on the optical signal, and the tunable filter element selects and tunes the wavelength of the optical signal. The optical signal generated by the laser generation gain unit is transmitted based on the above path, and deep compression of the line width can be achieved during the laser wavelength tuning process, so as to meet the requirements of line width compression of different laser wavelengths. By designing the positional relationship between the laser generation gain unit, the distributed scattering feedback unit, the first film and the second film, the optical signal after line width compression can be fully gain amplified before being output, thereby greatly reducing the energy consumption of the device.

[0036] The tunable filter element in the present invention first selects an optical signal of a specific wavelength before the optical signal is cyclically compressed, and then returns the selected optical signal of a specific wavelength to the distributed scattering feedback unit, so that the distributed scattering feedback unit only performs line width compression on the optical signal of the specific wavelength, and the laser generation gain unit only performs gain amplification on the optical signal of the specific wavelength. When the tunable filter element is tuned to another laser wavelength, when the optical signal with this wavelength is transmitted based on the optical path, the distributed scattering feedback unit performs line width compression on the optical signal of this wavelength, thereby achieving compression of the laser signal line width during the wavelength tuning process. The present invention achieves deep compression of laser line widths of different tuned wavelengths through cyclic compression of the distributed scattering feedback unit, and obtains an ultra-narrow line width optical signal with relatively high side mode suppression, which is simpler than conventional design structures.

[0037] Since the structure of the laser of the present invention is simple, the present invention is particularly applicable in the process of realizing laser integration and chipization. In addition, the second film 101 can also have a transmission characteristic, and the second film 101 is also connected to the second light collimating lens 4. After receiving the light signal, the second film 101 transmits a part of the light signal to the laser generating gain unit 1, and the other part is output through the second light collimating lens 4, thereby realizing double-end output.

[0038] In the above two embodiments, in order to achieve stable output of single longitudinal mode ultra-narrow linewidth optical signal, the tunable ultra-narrow linewidth laser of the present invention may also include an optical isolator, and the tunable filter element is connected to the optical isolator, and is used to output the obtained single longitudinal mode ultra-narrow linewidth optical signal through the optical isolator. The distributed scattering feedback unit 3 includes a special optical fiber with a high scattering coefficient, a waveguide structure made of a special gas material, or a special scattering waveguide engraved on a substrate (using femtosecond technology). The distributed scattering feedback unit is a unit that performs linewidth compression based on the distributed feedback effect. No matter whether it is the first end or the second end, after receiving the optical signal, the optical signal will be linewidth compressed. A part of the optical signal after linewidth compression is fed back from the optical signal receiving end, and the other part is transmitted from the other end. The present invention realizes self-matching of the laser wavelength and the effective distributed scattering cavity through the distributed scattering feedback unit; the distributed scattering feedback unit is all distributed scattering mechanisms including Rayleigh scattering, and the single longitudinal mode output of the laser is realized by the self-matching characteristics of the effective feedback cavity in the distributed scattering feedback unit to the laser wavelength. The present invention can achieve compression adjustment of the optical signal line width by adjusting the scattering coefficient and signal feedback ratio of the distributed scattering feedback unit 3, so that the line width of the output optical signal can be regulated. Specifically, since the optical signal is transmitted to the distributed scattering feedback unit 3 each time, the distributed scattering feedback unit 3 will perform line width compression once, and by adjusting the scattering coefficient of the distributed scattering feedback unit, the line width of each compression can be adjusted.

[0039] In the above two embodiments, the laser generation gain unit 1 may include a gain medium 102, which generates an initial optical signal with a wide spectrum under electrical excitation and transmits the generated optical signal to the first film 100 and the second film 101 respectively. After receiving the optical signal, the optical signal is gain-amplified (for example, the optical power is gain-amplified), and the gain-amplified optical signal is again transmitted to the first film 100 and the second film 101 respectively. The laser generation gain unit can cover any wavelength band of laser gain, and the compression mechanism is not wavelength-selective, and is suitable for deep compression of any wavelength band and any type of laser line width.

[0040] In the process of realizing laser integration and chip-based manufacturing in the above-mentioned embodiment, at least the laser generation gain unit 1, the distributed scattering feedback unit 3, the first light collimating lens 2, the second light collimating lens 4 and the tunable filter element 5 are integrated on the substrate. The present invention can realize integration and improve system stability by integrating various components on the substrate.

[0041] Wherein, the tunable filter element 5 can be a blazed grating Grating, combined with Figure 1 As shown, the blazed grating can be arranged along the light signal output direction of the second light collimating lens 4 at a corresponding preset angle (for example, 45 0 ) is set so that after the blazed grating receives the optical signal output by the second optical collimating lens 4, it tunes and outputs the optical signal corresponding to the preset wavelength perpendicular to its input direction. The present invention can select and tune the wavelength of the optical signal by adjusting the parameters of the blazed grating (such as wavelength, tuning accuracy, tuning range, etc.). Of course, the tunable filter can also include devices based on acousto-optic, thermo-optic and other tuning mechanisms. The distributed scattering feedback unit can include all dielectric waveguides with high scattering coefficients, which can be special optical fibers (Fiber) with high scattering coefficients, special gas materials, or special scattering waveguides written on the chip using femtosecond processing and other technologies. The gain spectrum of the laser gain unit can cover any wavelength band of the laser, and the invention does not have wavelength selectivity in the line width deep compression of laser wavelength tuning. In addition, the technology provided by this patent is applicable to both semiconductor type and fiber laser gain type lasers.

[0042] Those skilled in the art will readily appreciate other embodiments of the present invention after considering the specification and practicing the invention disclosed herein. This application is intended to cover any variations, uses or adaptations of the present invention that follow the general principles of the present invention and include common knowledge or customary techniques in the art that are not disclosed by the present invention. The specification and examples are to be considered exemplary only, and the true scope and spirit of the present invention are indicated by the following claims.

[0043] It should be understood that the present invention is not limited to the exact construction that has been described above and shown in the drawings and that various modifications and changes may be made without departing from the scope thereof. The scope of the present invention is limited only by the appended claims.

Claims

1. A tunable ultra-narrow linewidth laser, characterized in that: It comprises a laser generating gain unit, a distributed scattering feedback unit, a first light collimating lens, a second light collimating lens and a tunable filter element, wherein the first output end and the second output end of the laser generating gain unit are respectively provided with a first film and a second film, and both the first film and the second film have transmission and reflection characteristics, the first output end of the laser generating gain unit is connected to the first end of the distributed scattering feedback unit through the first film and the first light collimating lens in sequence, and the second output end is connected to the tunable filter element through the second film and the second light collimating lens in sequence; The laser generation gain unit is used to generate an initial optical signal with a wide spectrum and transmit the generated optical signal to the first film and the second film respectively; after receiving the optical signal, the first film transmits a part of the optical signal to the laser generation gain unit, and transmits the other part to the distributed scattering feedback unit through the first optical collimating lens; after receiving the optical signal, the second film transmits a part of the optical signal to the laser generation gain unit, and transmits the other part to the tunable filter element through the second optical collimating lens; After receiving the optical signal, the tunable filter element performs wavelength selection and tuning on the optical signal to obtain an optical signal with a specific wavelength, a part of which is transmitted to the second film through the second optical collimating lens, and the other part is directly output; after receiving the optical signal, the first end of the distributed scattering feedback unit performs line width compression on the optical signal, and transmits the optical signal fed back after line width compression to the first film through the first optical collimating lens; after receiving the optical signal, the laser generation gain unit performs gain amplification on the optical signal, and transmits the gain-amplified optical signal to the first film and the second film respectively; when reaching a steady state, the optical signal of the specific wavelength is cyclically line width compressed by the distributed scattering feedback unit, and the obtained single longitudinal mode ultra-narrow line width optical signal is output from the other end of the tunable filter element; The distributed scattering feedback unit also outputs the optical signal transmitted forward after line width compression through its second end.

2. A tunable ultra-narrow linewidth laser, characterized in that: It comprises a laser generating gain unit, a distributed scattering feedback unit, a first light collimating lens, a second light collimating lens and a tunable filter element, wherein the first output end and the second output end of the laser generating gain unit are respectively provided with a first film and a second film, the first film has transmission and reflection characteristics, the second film has reflection characteristics, the first output end of the laser generating gain unit is connected to the first end of the distributed scattering feedback unit through the first film and the first light collimating lens in sequence, the second output end is connected to the second film, and the second end of the distributed scattering feedback unit is connected to the tunable filter element; The laser generation gain unit is used to generate an initial optical signal with a wide spectrum and transmit the generated optical signal to the first film and the second film respectively; after receiving the optical signal, the first film transmits a part of the optical signal to the laser generation gain unit, and transmits the other part to the first end of the distributed scattering feedback unit through the first optical collimating lens; after receiving the optical signal, the second film transmits the optical signal to the laser generation gain unit; after receiving the optical signal, the laser generation gain unit performs gain amplification on the optical signal, and transmits the gain-amplified optical signal to the first film and the second film again respectively; After receiving the optical signal, the first end of the distributed scattering feedback unit performs line width compression on the optical signal, and transmits the optical signal fed back after line width compression to the first film through the first optical collimating lens, and transmits the optical signal transmitted forward after line width compression to the tunable filter element; after receiving the optical signal, the tunable filter element performs wavelength selection and tuning on the optical signal to obtain an optical signal with a specific wavelength, and a part of the optical signal with a specific wavelength is transmitted to the second end of the distributed scattering feedback unit, and the other part is directly output; After receiving the optical signal of the specific wavelength, the second end of the distributed scattering feedback unit performs line width compression on the optical signal, transmits the optical signal transmitted forward after line width compression to the first film through the first optical collimating lens, and transmits the optical signal fed back backward after line width compression to the tunable filter element; when reaching a steady state, the optical signal of the specific wavelength is cyclically line width compressed by the distributed scattering feedback unit, and the obtained single longitudinal mode ultra-narrow line width optical signal is output from the tunable filter element; The second film also has a transmission property and is also connected to a second light collimating lens. After receiving the light signal, the second film transmits a part of the light signal to the laser generating gain unit, and outputs the other part through the second light collimating lens.

3. The tunable ultra-narrow linewidth laser according to claim 1 or 2, characterized in that: It also includes an optical isolator, and the tunable filter element is connected to the optical isolator to output the obtained single longitudinal mode ultra-narrow linewidth optical signal through the optical isolator.

4. The tunable ultra-narrow linewidth laser according to claim 1 or 2, characterized in that: The distributed scattering feedback unit includes a special optical fiber with a high scattering coefficient, a waveguide structure made of a special gas material, or a special scattering waveguide engraved on a substrate.

5. The tunable ultra-narrow linewidth laser according to claim 1 or 2, characterized in that: The distributed scattering feedback unit is used to achieve self-matching between the laser wavelength and the effective distributed scattering cavity; the distributed scattering feedback unit is a distributed scattering mechanism represented by Rayleigh scattering, and cyclic compression adjustment of the optical signal line width is achieved by adjusting the scattering coefficient and signal feedback ratio of the distributed scattering feedback unit.

6. The tunable ultra-narrow linewidth laser according to claim 1 or 2, characterized in that: The laser generation gain unit includes a gain medium, which generates an initial light signal with a wide spectrum under electrical excitation and transmits the generated light signal to the first film and the second film respectively. After receiving the light signal, the light signal is gain amplified during the laser resonance process, and the gain-amplified light signal is again transmitted to the first film and the second film respectively.

7. The tunable ultra-narrow linewidth laser according to claim 1 or 2, characterized in that: At least the laser generation gain unit, the distributed scattering feedback unit, the first light collimating lens, the second light collimating lens and the tunable filtering unit are integrated on a substrate.

8. The tunable ultra-narrow linewidth laser according to claim 1 or 2, characterized in that: The laser generating gain unit can cover any wavelength band of laser gain, has no wavelength selectivity, and is suitable for deep compression of any wavelength band and any type of laser line width.

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