Brillouin laser and method for generating Brillouin laser

Abstract

The present application provides a Brillouin laser and a method for generating a Brillouin laser. The Brillouin laser includes: an optical fiber, a pump source, a ring cavity, and a dynamic grating unit; the pump source is configured to provide pump light of a first frequency; the ring cavity is configured to excite the pump light through the optical fiber into Stokes light of a second frequency; the dynamic grating unit is configured to perform filtering to ensure the single-mode state of the Brillouin laser. The solution of the present application improves the mode hopping phenomenon and transient multi-mode phenomenon of the traditional Brillouin laser, and realizes a single-frequency stable laser for a long time.

Description

Technical Field

[0001] The present application relates to the field of laser technology, and in particular to a Brillouin laser and a method for generating a Brillouin laser. Background Art

[0002] Brillouin lasers based on stimulated Brillouin scattering (SBS) are considered a technical approach to obtain narrow linewidth, low noise lasers. However, for Brillouin lasers in related technologies, transient multi-mode and mode hopping phenomena are prone to occur over a long period of time. Summary of the invention

[0003] In view of this, the purpose of the present application is to propose a Brillouin laser and a method for generating a Brillouin laser to solve or partially solve the above problems.

[0004] In a first aspect of the present application, a Brillouin laser is provided, comprising:

[0005] Optical fiber, pump source, ring cavity and dynamic grating unit;

[0006] The pump source is configured to provide pump light of a first frequency;

[0007] The ring cavity is configured to excite the pump light into Stokes light of a second frequency through the optical fiber;

[0008] The dynamic grating unit is configured to perform filtering to ensure the single-mode state of the Brillouin laser.

[0009] Optionally, the annular cavity comprises:

[0010] A first circulator, a second circulator, a first coupler and a fiber amplification unit;

[0011] The first circulator and the second circulator are configured to ensure unidirectional transmission of light in the ring cavity;

[0012] The first end of the first circulator is connected to the pump source, the second end of the first circulator is connected to the optical fiber amplification unit, and the third end of the first circulator is connected to the first end of the second circulator;

[0013] The second end of the second circulator is connected to the dynamic grating unit, and the third end of the second circulator is connected to the first coupler.

[0014] Optionally, the Brillouin laser further includes a second coupler and a third coupler;

[0015] The second coupler and the third coupler are configured to form a feedback loop and re-inject a portion of the Stokes light into the ring cavity through the first coupler to reduce the line width of the Brillouin laser.

[0016] Optionally, the dynamic grating unit includes: a saturated absorber and a uniform Bragg grating;

[0017] The uniform Bragg grating is configured to reflect light entering from the second circulator and passing through the saturable absorber;

[0018] The saturable absorber is configured to form a standing wave and a saturated absorption effect based on the light entering from the second circulator and the light reflected by the uniform Bragg grating to perform filtering.

[0019] Optionally, the second coupler is further configured to output a portion of the Stokes light.

[0020] Optionally, the third coupler is further configured to filter the re-injected Stokes light.

[0021] Optionally, the optical fiber amplification unit is configured to amplify the pump light; the optical fiber amplification unit comprises: a wavelength division multiplexer, a semiconductor laser and an erbium-doped optical fiber;

[0022] The first end of the wavelength division multiplexer is connected to the second end of the first circulator, and the second end of the wavelength division multiplexer is connected to the semiconductor laser and the erbium-doped optical fiber respectively.

[0023] In a second aspect of the present application, a method for generating a Brillouin laser is provided, which is applied to the Brillouin laser as described in the first aspect, and the method comprises:

[0024] Providing pump light of a first frequency using a pump source;

[0025] Using a ring cavity to excite the pump light into Stokes light of a second frequency through an optical fiber;

[0026] A dynamic grating unit is used for filtering to ensure the single-mode state of the Brillouin laser.

[0027] Optionally, the annular cavity includes a first coupler;

[0028] The method further includes: forming a feedback loop by using a second coupler and a third coupler and re-injecting a portion of the Stokes light into the ring cavity through the first coupler to reduce the line width of the Brillouin laser.

[0029] From the above, it can be seen that the Brillouin laser and the method for generating the Brillouin laser provided by the present application obtain Stokes light based on optical fiber, pump source and ring cavity, and use a dynamic grating unit to ensure the single-mode state of the Brillouin laser. The mode hopping phenomenon and transient multi-mode phenomenon of the traditional Brillouin laser are improved, and a single-frequency stable laser is achieved for a long time. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solutions in the present application or related technologies, the drawings required for use in the embodiments or related technical descriptions are briefly introduced below. Obviously, the drawings described below are only embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0031] Figure 1 is a schematic diagram of an exemplary Brillouin laser;

[0032] Figure 2 is a schematic diagram of another exemplary Brillouin laser;

[0033] Figure 3 A schematic diagram of the structure of a Brillouin laser according to an embodiment of the present application;

[0034] Figure 4 Schematic diagram of the process of generating Brillouin laser according to an embodiment of the present application. DETAILED DESCRIPTION

[0035] In order to make the objectives, technical solutions and advantages of the present application more clearly understood, the embodiments of the present application are described in detail below with reference to the accompanying drawings.

[0036] It should be noted that, unless otherwise defined, the technical terms or scientific terms used in the embodiments of the present application should be the usual meanings understood by people with ordinary skills in the field to which the present application belongs. The "first", "second" and similar words used in the embodiments of the present application do not represent any order, quantity or importance, but are only used to distinguish different components. "Including" or "comprising" and similar words mean that the elements or objects appearing in front of the word cover the elements or objects listed after the word and their equivalents, without excluding other elements or objects. "Connect" or "connected" and similar words are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. "Up", "down", "left", "right" and the like are only used to indicate relative positional relationships. When the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0037] Figure 1 A schematic diagram of an exemplary Brillouin laser 100 is shown. Figure 1 As shown, the Brillouin laser 100 includes: a pump laser source (DFB) 101, a circulator (CIR1) 102, a bandpass filter (TOF) 103, a 980nm light source pump (LD) 104, a wavelength division multiplexer (WDM) 105, an erbium-doped fiber (EDF) 106, and a coupler (OC) 107. The main working principle of the Brillouin laser 100 is: based on the pump laser source 101, a Brillouin pump laser with a relatively long line width is injected into the a' port of the circulator 102; based on the wavelength division multiplexer 105, the Brillouin effect is stimulated in the erbium-doped fiber 106 pumped by the 980nm light source 104 to generate backward propagating Stokes light. The backward Stokes light enters the bandpass filter 103 through the b' port and the c' port of the circulator 102, and is output through the 50:50 coupler 107.

[0038] For the Brillouin laser 100, erbium-doped fiber is used as the gain medium. Since it is essentially an erbium-doped fiber laser when no Brillouin pump light is injected, after the pump light is injected, under the gain competition, the Stokes light gradually increases and occupies a dominant position. However, since the single-mode state is ensured in the entire cavity mainly through the narrow-band Brillouin gain bandwidth and the erbium-doped fiber is easily interfered by the outside world, transient multi-mode and mode hopping phenomena are prone to occur over a long period of time. In addition, the suppression of the main mode and the remaining modes is relatively small. If the output power is too large, the side mode will also have a large power.

[0039] Figure 2 A schematic diagram of another exemplary Brillouin laser 200 is shown. Figure 2 As shown, the Brillouin laser 200 includes: a pump laser source 201, an isolator (ISO) 202, an erbium-doped fiber amplifier (EDFA) 203, an attenuator (VOA) 204, a first circulator 205, a polarization controller (PC) 206, dual couplers 207 and 208, a first single-mode optical fiber 209 (SMF1), a second circulator 210 and a second single-mode optical fiber 211 (SMF2). The main working principle of the Brillouin laser 200 is as follows: based on a pump laser source 201, the Brillouin pump light is amplified by an isolator 202 and an erbium-doped fiber amplifier 203, and then injected into a single-mode optical fiber 209 of more than a kilometer through an adjustable attenuator 204, thereby stimulating the Brillouin effect to generate Stokes light. Then, the dual couplers 207 and 208 form an optical filter to filter and reduce redundant modes. In addition, the second single-mode optical fiber 211 is used as a medium for Rayleigh scattering. On the basis of the Stokes light, the effect of weak distributed feedback is utilized to further reduce the noise of the laser.

[0040] For the Brillouin laser 200, single-mode optical fiber is used as the gain medium. Although filtering is performed through dual couplers 207 and 208, the mode hopping phenomenon can be reduced to a certain extent. However, due to the long cavity length, it is difficult to completely avoid the mode hopping itself, and the effect is poor.

[0041] In view of this, the embodiment of the present application provides a Brillouin laser and a method for generating a Brillouin laser, which obtains Stokes light based on an optical fiber, a pump source, and a ring cavity, and uses a dynamic grating unit to ensure the single-mode state of the Brillouin laser. The mode hopping phenomenon and transient multi-mode phenomenon of the traditional Brillouin laser are improved, and a single-frequency stable laser is achieved for a long time.

[0042] refer to Figure 3 , is a schematic diagram of the structure of the Brillouin laser 300 provided in the embodiment of the present application. Figure 3 As shown, the Brillouin laser 300 provided in the embodiment of the present application may include: an optical fiber, a pump source 301, a ring cavity and a dynamic grating unit.

[0043] Specifically, the pump source 301 is configured to provide pump light of a first frequency; the ring cavity is configured to excite the pump light into Stokes light of a second frequency through the optical fiber; and the dynamic grating unit is configured to perform filtering to ensure the single-mode state of the Brillouin laser.

[0044] In this embodiment, based on the pump source 301, pump light of a first frequency is injected into the ring cavity. For example, the wavelength of the pump light may be 1550 nm.

[0045] It can be understood that when no pump light is injected, the ring cavity is essentially an independent laser, and there is light of a certain frequency (wavelength) in the ring cavity, that is, there is a corresponding resonant mode in the ring cavity. After the pump light is injected, under the gain competition, the Stokes light gradually increases and occupies a dominant position.

[0046] In some embodiments, Figure 3 As shown, the annular cavity may include: a first circulator 302, a second circulator 306, a first coupler 309 and a fiber amplification unit.

[0047] Specifically, the first end a1 of the first circulator 302 is connected to the pump source 301, the second end b1 of the first circulator 302 is connected to the optical fiber amplification unit, and the third end c1 of the first circulator 302 is connected to the first end a2 of the second circulator 306; the second end b2 of the second circulator 306 is connected to the dynamic grating unit, and the third end b3 of the second circulator 306 is connected to the first coupler 309.

[0048] In some embodiments, the first circulator 302 and the second circulator 306 are configured to ensure unidirectional transmission of light in the ring cavity. Taking the first circulator 302 as an example, the transmission order of light through the first circulator 302 can only be the first end a1-the second end b1-the third end c1.

[0049] In some embodiments, the first circulator 302 and the second circulator 306 may be further configured to perform filtering. Since the first circulator 302 and the second circulator 306 themselves also have a certain bandwidth, only light in a certain wavelength band (eg, 1530-1560 nm) is allowed to pass.

[0050] In some embodiments, based on the pump source 301, pump light of a first frequency is injected into the ring cavity. Specifically, Figure 3 As shown, the pump light is injected into the first end a1 of the first circulator 302 .

[0051] In addition, as an optional embodiment, the first circulator 302 may be replaced by a coupler. However, it should be noted that if a coupler is used, compared with the first circulator 302, its power loss is greater.

[0052] In some embodiments, the fiber amplification unit is configured to amplify the pump light.

[0053] In some optional embodiments, such as Figure 3 As shown, the optical fiber amplification unit may further include: a wavelength division multiplexer 303, a semiconductor laser 304 and an erbium-doped optical fiber 305. Specifically, the first end of the wavelength division multiplexer 303 is connected to the second end b1 of the first circulator 302, and the second end of the wavelength division multiplexer 303 is connected to the semiconductor laser 304 and the erbium-doped optical fiber 305 respectively.

[0054] In some optional embodiments, the semiconductor laser 304 is configured to provide pumping to the erbium-doped fiber 305, thereby providing gain for laser formation.

[0055] In the related art, using a single-mode optical fiber to stimulate the Brillouin effect requires a length of several kilometers. In the embodiment of the present application, an erbium-doped optical fiber is used as the medium for Brillouin gain, and only a length of less than 10 meters is required to stimulate the Brillouin effect. Compared with using a single-mode optical fiber, the cavity length can be significantly reduced, which is more conducive to achieving a single-mode state.

[0056] In some optional embodiments, the emission wavelength of the semiconductor laser 304 is 900-980 nm. For example, the semiconductor laser 304 can be pumped by a 980 nm light source.

[0057] In some optional embodiments, the erbium-doped optical fiber 305 may also be replaced by an optical fiber doped with other rare earth elements, as long as the optical fiber doped with other rare earth elements can achieve the light amplification effect of the optical fiber amplifier unit.

[0058] It should be understood that when the pump light of the first frequency provided by the pump source 301 is not injected, the semiconductor laser 304 provides amplified energy, which is absorbed by the erbium-doped fiber 305 to generate the same photons as those in the ring cavity, thereby amplifying the light in the ring cavity, that is, the light propagating in the optical fiber undergoes an optical gain process. In response to the injection of the pump light of the first frequency, the gain of the semiconductor laser 304 is robbed.

[0059] As an optional embodiment, the power of the pump source 301 and the semiconductor laser 304 needs to be controlled within a certain range.

[0060] It should be understood that, for the pump source 301, if the power is too small, it is not enough to suppress the resonant mode in the ring cavity, resulting in the inability of Stokes light to dominate; if the power is too large, the pump light will rob the gain of the erbium-doped fiber 305, resulting in the inability to produce Brillouin gain effect, thereby resulting in the inability to generate Stokes light.

[0061] Furthermore, for the semiconductor laser 304, only appropriate power can enable the gain provided in the erbium-doped optical fiber 305 to amplify the Stokes light.

[0062] Therefore, a preliminary experiment can be conducted, and based on the components of the output light of the preliminary experiment, control instructions can be set to control the power of the pump source 301 and the semiconductor laser 304. Specifically, in the preliminary experiment, the components of the output light can be determined by connecting an external spectrometer and observing the spectrum image.

[0063] In this way, in response to the powers of the pump source 301 and the semiconductor laser 304 reaching the power thresholds respectively, the generated backward Stokes light enters from the second end b1 of the first circulator 302, and is output from the third end c1 of the first circulator 302, and then enters the dynamic grating unit through the first end a2 and the second end b2 of the second circulator 306.

[0064] It should be understood that in response to the power of the pump source 301 or the semiconductor laser 304 not reaching the power threshold, Stokes light cannot be generated. In addition, when the power does not reach the threshold, due to the unidirectional transmission effect of the first circulator 302 and the second circulator 306 on the light in the ring cavity, the pump light injected by the pump source 301 cannot pass through the first circulator 302 and cannot be output, resulting in the final output of only the light of the resonant mode in the ring cavity.

[0065] Specifically, the power threshold can be calculated by the following formula:

[0066]

[0067] Where R is the power reflectivity of the ring cavity; G is the linear gain; A eff is the effective mode field area of ​​erbium-doped fiber; g B is the Brillouin gain coefficient of the optical fiber; L eff is the effective fiber length.

[0068] In addition, although Stokes light is dominant under gain competition, and except for light with a wavelength close to the pump light (1550nm), light of other wavelengths can hardly grab the gain of the semiconductor laser 304, the output light may still have other modes besides the Stokes light. Therefore, it is necessary to further increase the suppression ratio between the main mode (Stokes light) and the side mode (resonant mode in the ring cavity and other light except the Stokes light) to avoid the occurrence of multi-mode phenomenon.

[0069] As an optional embodiment, Figure 3 As shown, the dynamic grating unit may include: a saturable absorber 307 and a uniform Bragg grating 308 .

[0070] Specifically, the uniform Bragg grating 308 is an all-fiber device formed by periodically modulating its refractive index. The uniform Bragg grating 308 is configured to reflect the light that enters from the second circulator 306 and passes through the saturable absorber 307 .

[0071] Furthermore, in some embodiments, the uniform Bragg grating 308 may also have an accurate wavelength selection function. The uniform Bragg grating 308 is a short section of optical fiber several mm long, and its basic characteristic is a narrowband optical filter centered on the resonant wavelength, with a bandwidth of the order of nm. In this way, based on the bandwidth of the uniform Bragg grating 308, only the pump light and the Stokes light are within its bandwidth, while the light generated by the semiconductor laser 304 (for example, 980nm light) is filtered out. However, since the bandwidth of the uniform Bragg grating 308 is relatively wide, it only has the effect of coarse filtering, and cannot filter out the light of the resonant mode in the ring cavity, and multimode phenomenon may still occur.

[0072] Further, in some embodiments, the saturated absorber 307 is configured to form a standing wave and a saturated absorption effect for filtering based on the light entering from the second circulator 306 and the light reflected by the uniform Bragg grating 308. On the basis of filtering out the light generated by the semiconductor laser 304, the light of other modes in the ring cavity is further filtered.

[0073] In this way, the incident light (light entering from the second circulator 306) and the reflected light (the incident light passes through the saturated absorber 307 and then is reflected by the uniform Bragg grating 308) form a stable standing wave in the saturated absorber 307, thereby generating a grating with a complex refractive index spatial modulation through the saturated absorption effect. And the formed grating has a narrower bandwidth than the uniform Bragg grating 308. Specifically, due to the occurrence of standing wave interference, the absorption coefficient of the saturated absorber 307 changes periodically, the absorption at the crest of the standing wave light field is very weak, and the absorption at the trough is very strong, thereby forming a periodic refractive index grating.

[0074] In some optional embodiments, a section of unpumped and low-concentration erbium-doped fiber can be inserted as a saturable absorber 307. For example, the absorption coefficient of the low-concentration erbium-doped fiber at 1530 nm does not exceed 20 dB / m.

[0075] In this way, the dynamic grating unit formed by the saturated absorber 307 and the uniform Bragg grating 308 can filter the light of other modes except the Stokes light in the ring cavity to suppress mode hopping and avoid the occurrence of multi-mode phenomenon.

[0076] In addition, in some optional embodiments, the length of the erbium-doped fiber 305 of the fiber amplifier unit and the low-concentration erbium-doped fiber forming the saturated absorber 307 of the dynamic grating unit will affect the power required by the pump source 301 and the semiconductor laser 304. For example, the length can be 2m, 4m, 6m, etc.

[0077] Furthermore, in some embodiments, Figure 3 As shown, the Brillouin laser 300 may further include: a second coupler 310 and a third coupler 311. Specifically, after the dynamic grating unit performs filtering and noise reduction, the second coupler 310 and the third coupler 311 are configured to form a feedback loop and re-inject part of the Stokes light into the ring cavity through the first coupler 309 to reduce the line width of the Brillouin laser.

[0078] It can be understood that re-injecting a portion of the light into the ring cavity can significantly reduce the noise performance of the excitation light in the cavity, thereby further reducing the line width of the Brillouin laser 300 .

[0079] In this embodiment, the second coupler 310 is further configured to output part of the Stokes light. Figure 3 As shown, part of the Stokes light is output from the point marked by the arrow.

[0080] In this embodiment, the third coupler 311 is further configured to filter the re-injected Stokes light, thereby further increasing the suppression ratio of the main mode and the side mode.

[0081] In addition, in some optional embodiments, the coupling ratios of the first coupler 309, the second coupler 310, and the third coupler 311 can be specifically set according to application requirements. For example, the coupling ratios of the first coupler 309, the second coupler 310, and the third coupler 311 can all be 50:50. Alternatively, the coupling ratio of the first coupler 309 is 90:10, and the coupling ratios of the second coupler 310 and the third coupler 311 are both 50:50. In this way, based on the coupler 309, 90% of the light is still in the ring cavity, and 10% of the light is distributed through 50% of the second coupler 310 and then redistributed through 50% of the third coupler 311, and finally the feedback light for the feedback loop is obtained. It can be understood that the coupling ratio of the first coupler 309 cannot be too large to avoid too much light output resulting in less light in the ring cavity, thereby causing the laser generation threshold to increase.

[0082] In some optional embodiments, the transmission function of the dual couplers (the second coupler 310 and the third coupler 311) calculated through the port connection is calculated by the transmission matrix of the coupler, and the obtained transmission function of the optical fiber filter is a periodic function. The transmittance bandwidth is changed by changing the connecting optical fiber length and the coupler ratio, thereby achieving narrowband filtering performance.

[0083] In some optional embodiments, FP cavity structures or weak distributed feedback media such as random gratings and high Rayleigh scattering optical fibers may also be used to achieve filtering and improve the single-mode performance of the laser.

[0084] In this way, the Brillouin laser 300 of the embodiment of the present application improves the Brillouin laser in the related art that relies solely on the Brillouin narrowband gain spectrum to maintain a single frequency, and can improve the phenomenon of transient mode hopping in the laser for a long time to a certain extent.

[0085] Based on the same technical concept, the present application also provides a method 400 for generating Brillouin laser.

[0086] like Figure 4 As shown, the method 400 may include the following steps:

[0087] Step S401, using the pump source 301 to provide pump light of a first frequency;

[0088] Step S402, using a ring cavity to excite the pump light through an optical fiber into Stokes light of a second frequency;

[0089] Step S403: Filtering is performed using a dynamic grating unit to ensure the single-mode state of the Brillouin laser.

[0090] In some embodiments, the ring cavity includes a first coupler 309. The method further includes: using a second coupler 310 and a third coupler 311 to form a feedback loop and re-injecting part of the Stokes light into the ring cavity through the first coupler 309 to reduce the line width of the Brillouin laser.

[0091] In some optional embodiments, the ring cavity further includes: a first circulator 302 and a second circulator 306. The method further includes: using the first circulator 302 and the second circulator 306 to ensure unidirectional transmission of light in the ring cavity.

[0092] In some optional embodiments, the dynamic grating unit includes: a saturated absorber 307 and a uniform Bragg grating 308. The method further includes:

[0093] The uniform Bragg grating 308 is used to reflect the light entering from the second circulator 306 and passing through the saturated absorber 307. The saturated absorber 307 is used to form a standing wave and a saturated absorption effect based on the light entering from the second circulator 306 and the light reflected by the uniform Bragg grating 308 for filtering.

[0094] In some optional embodiments, the method further includes: utilizing a second coupler 310 to output a portion of the Stokes light.

[0095] It should be noted that the above describes some embodiments of the present application. Other embodiments are within the scope of the appended claims. In some cases, the actions or steps recorded in the claims can be performed in an order different from that in the above embodiments and still achieve the desired results. In addition, the processes depicted in the accompanying drawings do not necessarily require the specific order or continuous order shown to achieve the desired results. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0096] The method of the above embodiment is applied to the corresponding Brillouin laser in any of the above embodiments, and has the beneficial effects of the corresponding embodiment, which will not be described in detail here.

[0097] Those skilled in the art should understand that the discussion of any of the above embodiments is merely illustrative and is not intended to imply that the scope of the present application (including the claims) is limited to these examples. In line with the concept of the present application, the technical features in the above embodiments or different embodiments may also be combined, and there are many other variations of different aspects of the embodiments of the present application as described above, which are not provided in detail for the sake of simplicity.

[0098] Although the present application has been described in conjunction with specific embodiments thereof, many alternatives, modifications and variations of these embodiments will be apparent to those skilled in the art in light of the foregoing description.

[0099] The embodiments of the present application are intended to cover all such substitutions, modifications and variations that fall within the broad scope of the appended claims. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the embodiments of the present application should be included in the scope of protection of the present application.

Claims

1. A Brillouin laser, characterized in that: include: Optical fiber, pump source, ring cavity and dynamic grating unit; The pump source is configured to provide pump light of a first frequency; The ring cavity is configured to excite the pump light into Stokes light of a second frequency through the optical fiber; The dynamic grating unit is configured to perform filtering to ensure a single-mode state of the Brillouin laser; Wherein, the annular cavity comprises: A first circulator, a second circulator, a first coupler and a fiber amplification unit; The first circulator and the second circulator are configured to ensure unidirectional transmission of light in the ring cavity; The first end of the first circulator is connected to the pump source, the second end of the first circulator is connected to the optical fiber amplification unit, and the third end of the first circulator is connected to the first end of the second circulator; The second end of the second circulator is connected to the dynamic grating unit, and the third end of the second circulator is connected to the first coupler; There is a corresponding resonance mode in the annular cavity. After the pump light is injected, the Stokes light gradually increases under gain competition and occupies a dominant position.

2. The Brillouin laser according to claim 1, characterized in that The Brillouin laser also includes a second coupler and a third coupler; The second coupler and the third coupler are configured to form a feedback loop and re-inject a portion of the Stokes light into the ring cavity through the first coupler to reduce the line width of the Brillouin laser.

3. The Brillouin laser according to claim 1, characterized in that The dynamic grating unit includes: a saturated absorber and a uniform Bragg grating; The uniform Bragg grating is configured to reflect light entering from the second circulator and passing through the saturable absorber; The saturable absorber is configured to form a standing wave and a saturated absorption effect based on the light entering from the second circulator and the light reflected by the uniform Bragg grating to perform filtering.

4. The Brillouin laser according to claim 2, characterized in that: The second coupler is further configured to output a portion of the Stokes light.

5. The Brillouin laser according to claim 2, characterized in that: The third coupler is further configured to filter the re-injected Stokes light.

6. The Brillouin laser according to claim 1, characterized in that: The optical fiber amplification unit is configured to amplify the pump light; The optical fiber amplification unit comprises: a wavelength division multiplexer, a semiconductor laser and an erbium-doped optical fiber; The first end of the wavelength division multiplexer is connected to the second end of the first circulator, and the second end of the wavelength division multiplexer is connected to the semiconductor laser and the erbium-doped optical fiber respectively.

7. A method for generating Brillouin laser, characterized in that: Applied to the Brillouin laser as claimed in any one of claims 1 to 6, the method comprising: Providing pump light of a first frequency using a pump source; Using a ring cavity to excite the pump light into Stokes light of a second frequency through an optical fiber; A dynamic grating unit is used for filtering to ensure the single-mode state of the Brillouin laser.

8. The method according to claim 7, characterized in that The annular cavity includes a first coupler; The method further includes: forming a feedback loop by using a second coupler and a third coupler and re-injecting a portion of the Stokes light into the ring cavity through the first coupler to reduce the line width of the Brillouin laser.

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