Single-frequency fiber laser with adjustable wavelength

Abstract

The utility model discloses a single-frequency fiber laser with an adjustable wavelength. The single-frequency optical fiber laser comprises a first pumping source, a first wavelength division multiplexer, a first gain optical fiber, a circulator, a wavelength tuning module, a first coupler and a Fabry-Perot etalon which are connected through optical fibers. The first wavelength division multiplexer, the first gain fiber, the circulator, the first coupler and the Fabry-Perot etalon form an annular cavity, the first end and the third end of the circulator are connected into the annular cavity, and the second end of the circulator is connected with the wavelength tuning module; and the wavelength tuning module comprises a second gain optical fiber, a tunable filter and a total reflection mirror which are connected in sequence. According to the utility model, wide-range tunable single-frequency narrow-linewidth laser output is realized. The laser has the advantages of wide tuning range, single longitudinal mode, narrow linewidth, high stable power output, compact structure, small volume, low heat and the like, so that the laser has important application prospects in the fields of single-chip laboratories, medical diagnosis, dermatology and the like.

Description

Technical Field

[0001] This utility model relates to the field of laser technology, and in particular to a wavelength-tunable single-frequency fiber laser. Background Technology

[0002] A tunable laser is a laser whose output wavelength can be continuously changed within a certain range. These lasers have a wide range of applications, including spectroscopy, photochemistry, medicine, biology, integrated optics, pollution monitoring, semiconductor material processing, information processing, and communications. Single-frequency narrow-linewidth lasers have extensive applications in optical sensing and high-precision spectroscopy, particularly as light sources for fiber optic sensors. They possess characteristics such as resistance to electromagnetic interference, safety, small size, and remote controllability, and can be applied in distributed fiber optic sensors, laser positioning / rangefinders, fiber optic underwater sonar arrays, and seabed oil exploration and seismic detection.

[0003] Semiconductor tunable lasers are the most commonly used tunable lasers in current technology. Based on their operating principles, semiconductor tunable lasers can be categorized into current-controlled, temperature-controlled, and mechanically controlled types. Current-controlled technology achieves wavelength tuning by changing the injection current. Its advantages include nanosecond-level tuning speed and a wide tuning bandwidth, but its disadvantages include relatively low output power and a wide linewidth (in the MHz range). Temperature-controlled technology changes the refractive index of the laser's active region by controlling temperature, thereby altering the output wavelength. Its advantages include simplicity, but its disadvantages include slow tuning speed and a narrow tunable bandwidth (only a few nm). Mechanically controlled technology primarily uses MEMS (Micro-Electro-Mechanical Systems) technology to select the wavelength. Its advantages include a large tunable bandwidth and high output power, but its disadvantages include a wide output linewidth (in the MHz range). Utility Model Content

[0004] This invention provides a wavelength-tunable single-frequency fiber laser. The single-frequency fiber laser employs an optimized traveling-wave cavity structure, incorporating a Fabry-Perot etalon device within the cavity and a tunable filter outside the cavity to select the wavelength, thereby achieving wide-range tunable single-frequency narrow-linewidth laser output. This laser possesses advantages such as a wide tuning range, single longitudinal mode, narrow linewidth, high stable power output, compact structure, small size, and low heat generation, making it promising for applications in single-chip laboratories, medical diagnostics, and dermatology.

[0005] This invention provides a wavelength-tunable single-frequency fiber laser, comprising: a first pump source, a first wavelength division multiplexer, a first gain fiber, a circulator, a wavelength tuning module, a first coupler, and a Fabry-Perot etalon connected by optical fibers.

[0006] The first wavelength division multiplexer, the first gain fiber, the circulator, the first coupler, and the Fabry-Perot etalon form a ring cavity. The first and third ends of the circulator are connected to the ring cavity, and the second end of the circulator is connected to the wavelength tuning module.

[0007] The wavelength tuning module includes a second gain fiber, a tunable filter, and a total reflection mirror connected in sequence.

[0008] Optionally, the output of the first pump source is connected to the first input of the first wavelength division multiplexer, the output of the first wavelength division multiplexer is connected to the first end of the first gain fiber, the second end of the first gain fiber is connected to the first end of the circulator, the third end of the circulator is connected to the input of the first coupler, the first output of the first coupler is connected to the first end of the Fabry-Perot etalon, the second output of the first coupler is the output of a single-frequency laser, and the second end of the Fabry-Perot etalon is connected to the second input of the first wavelength division multiplexer.

[0009] The second end of the circulator is connected to the first end of the second gain fiber, the second end of the second gain fiber is connected to the first end of the tunable filter, and the second end of the tunable filter is connected to the total reflection mirror.

[0010] Optionally, a first isolator may also be disposed within the annular cavity.

[0011] Optionally, the input terminal of the first isolator is connected to the first output terminal of the first coupler, and the output terminal of the first isolator is connected to the first end of the Fabry-Perot etalon.

[0012] Optionally, it may also include at least one fiber optic amplifier, the input of which is connected to the second output of the first coupler.

[0013] Optionally, a second isolator is also included, wherein the input of the second isolator is connected to the second output of the first coupler, and the output of the second isolator is connected to the input of the fiber amplifier.

[0014] Optionally, the fiber amplifier includes a second pump source, a second wavelength division multiplexer, and a third gain fiber. The output of the second pump source is connected to the first input of the second wavelength division multiplexer, the second input of the second wavelength division multiplexer is connected to the second output of the first coupler, and the output of the second wavelength division multiplexer is connected to the first end of the third gain fiber.

[0015] Optionally, the fiber amplifier further includes a third isolator, a second coupler, and a photodetector. The input end of the third isolator is connected to the second end of the third gain fiber, the output end of the third isolator is connected to the input end of the second coupler, the first output end of the second coupler is used to output the amplified single-frequency laser, and the second output end of the second coupler is connected to the photodetector.

[0016] Optionally, both the first pump source and the second pump source include a 976nm semiconductor laser, and the first gain fiber, the second gain fiber, and the third gain fiber all include ytterbium-doped fiber.

[0017] Optionally, the single-frequency fiber laser has an output wavelength range of 1030nm to 1093nm.

[0018] The wavelength-tunable single-frequency fiber laser provided in this embodiment includes: a first pump source, a first wavelength division multiplexer, a first gain fiber, a circulator, a wavelength tuning module, a first coupler, and a Fabry-Perot etalon connected by optical fibers. The first wavelength division multiplexer, the first gain fiber, the circulator, the first coupler, and the Fabry-Perot etalon form a ring cavity. The first and third ends of the circulator are connected into the ring cavity, and the second end of the circulator is connected to the wavelength tuning module. The wavelength tuning module includes a second gain fiber, a tunable filter, and a total reflection mirror connected in sequence. Pump light is provided by the first pump source, and the pump light passes through the first wavelength division multiplexer and is incident on the first gain fiber, where it is absorbed to generate laser light. The Fabry-Perot etalon is used to generate laser light within the entire wavelength tuning range. The tunable filter acts as a frequency-selective device; the desired wavelength can be obtained by controlling the wavelength of the tunable filter. In a single-frequency fiber laser, after the oscillating beam is amplified by a ring cavity, part of the energy is output as laser light from the second output end of the first coupler, while the remaining portion continues to oscillate within the cavity through the first output end of the first coupler. This oscillation then enters a saturable absorber formed by the second gain fiber through the second end of the circulator. After frequency selection by a tunable filter, the light is reflected by a total reflection mirror. The incident and reflected light interfere within the saturable absorber, resulting in the strongest interference for a specific longitudinal mode. This saturates the absorber, creating a spatial aperture effect that minimizes absorption of that wavelength and prevents the formation of standing waves for other longitudinal modes. Because standing waves cannot form, the fiber's absorption loss is relatively high, making it difficult for other longitudinal modes to gain dominance and causing mode hopping. The saturable absorber effectively suppresses other longitudinal mode oscillations, achieving stable single-mode operation and producing wavelength-tunable, narrow-linewidth single-frequency laser light. This utility model provides a single-frequency fiber laser with an optimized traveling-wave cavity structure. A Fabry-Perot etalon device is added inside the cavity, and a tunable filter is added outside the cavity to select the wavelength, thereby realizing a wide-range tunable single-frequency narrow-linewidth laser output. It has advantages such as wide tuning range, single longitudinal mode, narrow linewidth, high stable power output, compact structure, small size, and low heat generation, which makes it have important application prospects in fields such as single-chip laboratory, medical diagnostics, and dermatology.

[0019] It should be understood that the description in this section is not intended to identify key or essential features of the embodiments of this utility model, nor is it intended to limit the scope of this utility model. Other features of this utility model will become readily apparent from the following description. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of this utility model, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 A schematic diagram of a wavelength-tunable single-frequency fiber laser provided for an embodiment of this utility model;

[0022] Figure 2 A schematic diagram of another wavelength-tunable single-frequency fiber laser provided for an embodiment of this utility model;

[0023] Figure 3 A schematic diagram of another wavelength-tunable single-frequency fiber laser provided for an embodiment of this utility model;

[0024] Figure 4 A schematic diagram of another wavelength-tunable single-frequency fiber laser provided for an embodiment of this utility model;

[0025] Figure 5 A schematic diagram of another wavelength-tunable single-frequency fiber laser provided for an embodiment of this utility model;

[0026] Figures 6-9 The output spectra of the wavelength-tunable single-frequency fiber laser provided in the embodiments of this utility model are shown respectively.

[0027] Figure 10 The image shows the linewidth of a single-wavelength laser output measured using the self-heterodyne method.

[0028] Figure 11 This is a graph showing the stability of output power. Detailed Implementation

[0029] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the protection scope of the present invention.

[0030] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this utility model are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the utility model described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0031] Figure 1 A schematic diagram of a wavelength-tunable single-frequency fiber laser provided for an embodiment of this utility model, with reference to... Figure 1 The wavelength-tunable single-frequency fiber laser includes: a first pump source 10, a first wavelength division multiplexer 20, a first gain fiber 30, a circulator 40, a wavelength tuning module 50, a first coupler 60, and a Fabry-Perot etalon 70 connected by optical fibers; the first wavelength division multiplexer 20, the first gain fiber 30, the circulator 40, the first coupler 60, and the Fabry-Perot etalon 70 form a ring cavity; the first end 1 and the third end 3 of the circulator 40 are connected into the ring cavity, and the second end 2 of the circulator 40 is connected to the wavelength tuning module 50; the wavelength tuning module 50 includes a second gain fiber 51, a tunable filter 52, and a total reflection mirror 53 connected in sequence.

[0032] In this embodiment, the wavelength-tunable single-frequency fiber laser can be a 1μm band single-frequency narrow-linewidth laser, the first pump source 10 can be a 976nm semiconductor laser (semiconductor laser diode LD), the first gain fiber 30 and the second gain fiber 51 can be ytterbium-doped fiber (YDF), and the first wavelength division multiplexer 20 can be a 980 / 1064nm polarization-maintaining wavelength division multiplexer (WDM). A circulator is a multi-port device that sequentially transmits incident waves entering any of its ports to the next port according to the direction determined by a static polarization magnetic field. A circulator is a non-reversible device with multiple ports. For example, if a signal is input from port 1, the signal can only be output from port 2; similarly, a signal input from port 2 can only be output from port 3, and so on, hence the name circulator. In this embodiment, the circulator 40 can be a 1064nm polarization-maintaining circulator. The first coupler 60 can be a 1064nm coupler with a splitting ratio of 50:50. After passing through the first coupler 60, 50% of the laser light is output, and the remaining 50% continues to propagate in the ring cavity. In other embodiments, the splitting ratio of the first coupler 60 can be designed according to actual conditions, and this embodiment of the present invention does not limit this. The Fabry-Perot etalon 70 utilizes the Fabry-Perot multi-beam interference principle. It forms a multi-beam interference cavity by coating the two surfaces that make up the interference cavity with optical reflective films of different reflectivities, which is equivalent to a narrowband filter used to generate laser light across the entire wavelength tuning range.

[0033] The principle of the wavelength-tunable single-frequency fiber laser provided in this embodiment is as follows: Pump light is provided by a first pump source 10. The pump light passes through a first wavelength division multiplexer 20 and is incident on a first gain fiber 30, where it is absorbed to generate laser light. A Fabry-Perot etalon 70 is used to generate laser light across the entire wavelength tuning range. A tunable filter 51 serves as a frequency selection device; the desired wavelength can be obtained by controlling the wavelength of the tunable filter 51. In a single-frequency fiber laser, after the oscillating beam is amplified by a ring cavity, part of the energy is output as laser light from the second output end of the first coupler 60, while the remaining portion continues to oscillate within the cavity through the first output end of the first coupler 60. This oscillation then enters the saturable absorber formed by the second gain fiber 51 through the second end of the circulator 40. After frequency selection by the tunable filter 52, the light is reflected by the total reflection mirror 53. The incident and reflected light interfere within the saturable absorber, resulting in the strongest interference for a specific longitudinal mode. This saturates the absorber, creating a spatial hole-burning effect that minimizes absorption of that wavelength. Simultaneously, it prevents the formation of standing waves for other longitudinal modes. Because standing waves cannot form, the fiber's absorption loss is relatively high, making it difficult for other longitudinal modes to gain dominance and causing mode hopping. The saturable absorber effectively suppresses other longitudinal mode oscillations, achieving stable single-mode operation and generating wavelength-tunable single-frequency narrow-linewidth laser light.

[0034] Continue to refer to Figure 1 Optionally, the output of the first pump source 10 is connected to the first input of the first wavelength division multiplexer 20, the output of the first wavelength division multiplexer 20 is connected to the first end of the first gain fiber 30, the second end of the first gain fiber 30 is connected to the first end 1 of the circulator 40, the third end 3 of the circulator 40 is connected to the input of the first coupler 60, the first output of the first coupler 60 is connected to the first end of the Fabry-Perot etalon 70, the second output of the first coupler 60 is the output of a single-frequency laser, the second end of the Fabry-Perot etalon 70 is connected to the second input of the first wavelength division multiplexer 40; the second end 2 of the circulator 40 is connected to the first end of the second gain fiber 51, the second end of the second gain fiber 51 is connected to the first end of the tunable filter 52, and the second end of the tunable filter 52 is connected to the total reflection mirror 53.

[0035] It should be noted that, Figure 1 Only one possible connection relationship is shown. Without affecting the function, the position of some components can be adjusted according to the actual situation. The specific implementation can be designed according to the actual situation.

[0036] This utility model provides a single-frequency fiber laser with an optimized traveling-wave cavity structure. A Fabry-Perot etalon device is added inside the cavity, and a tunable filter is added outside the cavity to select the wavelength, thereby realizing a wide-range tunable single-frequency narrow-linewidth laser output. It has advantages such as wide tuning range, single longitudinal mode, narrow linewidth, high stable power output, compact structure, small size, and low heat generation, which makes it have important application prospects in fields such as single-chip laboratory, medical diagnostics, and dermatology.

[0037] Figure 2 A schematic diagram of another wavelength-tunable single-frequency fiber laser provided in this embodiment of the present invention is shown below. Figure 2 Optionally, the wavelength-tunable single-frequency fiber laser also includes a first isolator 80 disposed within the ring cavity.

[0038] The first isolator 80 can be a 1064nm fiber optic isolator, used to ensure unidirectional laser transmission and guarantee that the oscillating beam in the ring cavity is in a traveling wave state, preventing the formation of standing waves that could cause spatial hole burning. Optional, see further reference. Figure 2 The input terminal of the first isolator 80 is connected to the first output terminal of the first coupler 60, and the output terminal of the first isolator 80 is connected to the first terminal of the Fabry-Perot etalon 70.

[0039] In other embodiments, the position of the first isolator 80 can be designed according to actual needs, and this utility model does not limit it in this regard.

[0040] Figure 3This is a schematic diagram of another wavelength-tunable single-frequency fiber laser provided in an embodiment of the present invention, with reference to... Figure 3 Optionally, the wavelength-tunable single-frequency fiber laser also includes at least one fiber amplifier 90, the input of which is connected to the second output of the first coupler 60.

[0041] By setting up fiber amplifier 90, the optical power of the single-frequency laser output from the wavelength-tunable single-frequency fiber laser can be amplified to meet the power requirements of different application scenarios.

[0042] Optional, continue to refer to Figure 3 The fiber amplifier 90 includes a second pump source 91, a second wavelength division multiplexer 92, and a third gain fiber 93. The output end of the second pump source 91 is connected to the first input end of the second wavelength division multiplexer 92, the second input end of the second wavelength division multiplexer 92 is connected to the second output end of the first coupler 60, and the output end of the second wavelength division multiplexer 92 is connected to the first end of the third gain fiber 93.

[0043] The second pump source 91 can be the same as the first pump source 10, and the third gain fiber 93 can be the same as the first gain fiber 30 and the second gain fiber 51. That is, both the first pump source 10 and the second pump source 91 include a 976nm semiconductor laser, and the first gain fiber 30, the second gain fiber 51, and the third gain fiber 93 all include ytterbium-doped fiber. The second wavelength division multiplexer 92 can be a 980 / 1064nm polarization-maintaining wavelength division multiplexer. In specific implementations, to achieve stable single-frequency output, all components used in the laser are polarization-maintaining devices to avoid mode hopping caused by polarization instability. Optionally, the single-frequency fiber laser provided in this embodiment has an output wavelength range of 1030nm to 1093nm.

[0044] Continue to refer to Figure 3 Optionally, the wavelength-tunable single-frequency fiber laser also includes a second isolator 81, the input of which is connected to the second output of the first coupler 60, and the output of which is connected to the input of the fiber amplifier 90.

[0045] The second isolator 81 is used to ensure unidirectional transmission of the single-frequency laser output from the ring cavity, and to prevent the output laser from returning to the ring cavity and affecting the stability of the single-frequency laser.

[0046] Figure 4 This is a schematic diagram of another wavelength-tunable single-frequency fiber laser provided in an embodiment of the present invention, with reference to... Figure 4Optionally, the fiber amplifier 90 also includes a third isolator 94, a second coupler 95, and a photodetector 96. The input end of the third isolator 94 is connected to the second end of the third gain fiber 93, the output end of the third isolator 94 is connected to the input end of the second coupler 95, the first output end of the second coupler 95 is used to output the amplified single-frequency laser, and the second output end of the second coupler 95 is connected to the photodetector 96.

[0047] The third isolator 94 is used to ensure unidirectional laser transmission. The second coupler 95 can be a coupler with a splitting ratio of 1:99, with 99% of the optical power output. Of this, 1% of the optical power is received by the photodetector 96. The photodetector 96 can be a PIN photodetector, which facilitates the implementation of constant power output (APC) control mode in the circuit and improves the stability of the output power.

[0048] In one specific embodiment, for example, Figure 5 This is a schematic diagram of another wavelength-tunable single-frequency fiber laser provided in an embodiment of the present invention, with reference to... Figure 5This wavelength-tunable single-frequency fiber laser consists of a seed laser and a fiber amplifier. The seed laser includes a first pump source 10, a first wavelength division multiplexer 20, a first gain fiber 30, a circulator 40, a second gain fiber 51, a tunable filter 52, a total reflection mirror 53, a first coupler 60, a Fabry-Perot etalon 70, and a first isolator 80. The fiber amplifier includes a second pump source 91, a second wavelength division multiplexer 92, a third gain fiber 93, a third isolator 94, a second coupler 95, and a photodetector 96. A second isolator 81 is also included between the seed laser and the fiber amplifier. In the seed laser, the gain medium of the fiber laser is the first gain fiber 30 connected after the first wavelength division multiplexer 20 in the ring cavity. The first gain fiber 30 is a highly doped ytterbium-doped fiber with a peak absorption coefficient of 250 dB / m at a wavelength of 976 nm and a length of 1.2 m. The first pump source 10 is a 976nm fiber grating frequency-stabilized semiconductor laser with a maximum pump power of 800mW. The first gain fiber 30 absorbs the pump light to generate laser light, which then passes through the second end 2 of the circulator 40 and enters the second gain fiber 51. The second gain fiber 51 is also a highly doped ytterbium-doped fiber with a peak absorption coefficient of 250dB / m at 976nm wavelength and a length of 2.6m. The laser light then enters the tunable filter 52 and the total reflection mirror 53. After reflection by the total reflection mirror 53, the light re-enters the tunable filter 52 and the second gain fiber 51, then enters the third end 3 of the circulator 40 and the first isolator 80, where it oscillates within the cavity. The first isolator 80 ensures unidirectional operation of the laser within the cavity, preventing standing waves. The Fabry-Perot etalon 70 within the cavity operates in the wavelength range of 1030nm to 1093nm, generating laser light in the 1030nm to 1093nm band, thus enabling wide-range wavelength tunability. The second gain fiber 51, tunable filter 52, and total reflection mirror 53 at the second end 2 of circulator 40 constitute the key components of the fiber laser. Due to the optical isolation effect of circulator 40, the pump light entering the cavity cannot enter the second end 2 of circulator 40, so the second gain fiber 51 is unpumped. The laser enters the second end 2 from the first end 1 of circulator 40 and forms a standing wave interference with the reflected light from mirror 53. When the optical power and ytterbium-doped fiber length are appropriate, saturation absorption occurs at the peak of the standing wave, inducing spatial hole burning, which is the self-written fiber grating. Because of its long length and extremely narrow reflection bandwidth, and because its reflection center wavelength has adaptive characteristics, this type of fiber grating can effectively suppress the generation of mode hopping and side modes. The phenomenon of easy mode hopping in fiber lasers is effectively solved. The single longitudinal mode laser generated in the cavity enters the fiber amplifier through the second output end of the first coupler 60.Because the gain of ytterbium-doped fiber is different at different wavelengths in the range of 1030nm to 1093nm, the output power of the laser at different wavelengths will vary greatly. When the power of the first pump source 10 is 800mW, the output power of the laser at different wavelengths ranges from 1mW to 10mW.

[0049] The fiber amplifier is a typical ytterbium-doped amplifier structure. The only difference is that a trade-off was made when selecting the length of the third gain fiber 93. To ensure that the signal can be effectively amplified in the wavelength range of 1030nm to 1093nm, the peak absorption coefficient of the third gain fiber 93 at a wavelength of 976nm is 250dB / m. The length of the third gain fiber 93 was finally optimized to 4.5m, and the APC control mode of the circuit ensured that a stable output of 20mW power could be achieved at different wavelengths.

[0050] In this embodiment of the invention, a spectrometer was used for testing. This spectrometer has a maximum accuracy of 0.02 nm. The desired laser wavelength was obtained by adjusting the wavelength of the tunable filter. Figures 6-9 The images show the output spectra of a wavelength-tunable single-frequency fiber laser provided in this embodiment of the invention, with a side-mode suppression ratio (SMSR) > 37 dB and a wavelength tuning accuracy of 0.1 nm. Figure 10 The image shows the linewidth of a single-wavelength laser output measured using the self-heterodyne method. Figure 11 This is a graph showing the output power stability test results. Figure 10 It can be seen that the linewidth of a single-frequency laser is <1.2kHz, from Figure 11 It can be seen that the output power stability is <1.5% after 2.5 hours (h), and the polarization extinction ratio (PER) is >25dB.

[0051] The wavelength-tunable single-frequency fiber laser provided in this embodiment employs a traveling-wave cavity optical path structure, which has the following advantages: ① The overall cavity length is approximately 10 meters, which increases the number of oscillations within the cavity, resulting in a single-frequency laser with a very narrow linewidth; ② Ytterbium-doped fiber is used as a saturable absorber outside the cavity, which helps suppress the generation of other multiple longitudinal modes and achieves stable single-frequency laser output; ③ A tunable filter and a total reflection mirror replace the general single-wavelength etalon, allowing any desired wavelength to be obtained based on the wavelength selection of the tunable filter, thus achieving wide-range tunability; ④ The addition of a Fabry-Perot etalon operating over a wide range within the cavity enables a wide range of laser output, providing the possibility for wide-range single-frequency laser output; ⑤ To achieve stable single-frequency output, all components used in the laser are polarization-maintaining devices, avoiding mode-hopping phenomena caused by polarization instability; ⑥ The amplifier output adopts APC control mode, ensuring that the output power is 20mW for any wavelength in the entire wavelength range from 1030nm to 1093nm.

[0052] The specific embodiments described above do not constitute a limitation on the scope of protection of this utility model. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this utility model should be included within the scope of protection of this utility model.

Claims

1. A wavelength-tunable single-frequency fiber laser, characterized by, include: The first pump source, first wavelength division multiplexer, first gain fiber, circulator, wavelength tuning module, first coupler, and Fabry-Perot etalon are connected by optical fiber. The first wavelength division multiplexer, the first gain fiber, the circulator, the first coupler, and the Fabry-Perot etalon form a ring cavity. The first and third ends of the circulator are connected to the ring cavity, and the second end of the circulator is connected to the wavelength tuning module. The wavelength tuning module includes a second gain fiber, a tunable filter, and a total reflection mirror connected in sequence.

2. The wavelength-tunable single-frequency fiber laser of claim 1, wherein, The output of the first pump source is connected to the first input of the first wavelength division multiplexer. The output of the first wavelength division multiplexer is connected to the first end of the first gain fiber. The second end of the first gain fiber is connected to the first end of the circulator. The third end of the circulator is connected to the input of the first coupler. The first output of the first coupler is connected to the first end of the Fabry-Perot etalon. The second output of the first coupler is the output of a single-frequency laser. The second end of the Fabry-Perot etalon is connected to the second input of the first wavelength division multiplexer. The second end of the circulator is connected to the first end of the second gain fiber, the second end of the second gain fiber is connected to the first end of the tunable filter, and the second end of the tunable filter is connected to the total reflection mirror.

3. The wavelength tunable single frequency fiber laser of claim 2, wherein, It also includes a first isolator disposed within the annular cavity.

4. The wavelength-tunable single-frequency fiber laser according to claim 3, characterized in that, The input terminal of the first isolator is connected to the first output terminal of the first coupler, and the output terminal of the first isolator is connected to the first end of the Fabry-Perot etalon.

5. The wavelength tunable single frequency fiber laser of claim 2, wherein, It also includes at least one fiber optic amplifier, the input of which is connected to the second output of the first coupler.

6. The wavelength tunable single frequency fiber laser of claim 5, wherein, It also includes a second isolator, the input of which is connected to the second output of the first coupler, and the output of which is connected to the input of the fiber amplifier.

7. The wavelength tunable single frequency fiber laser of claim 5, wherein, The fiber amplifier includes a second pump source, a second wavelength division multiplexer, and a third gain fiber. The output of the second pump source is connected to the first input of the second wavelength division multiplexer, the second input of the second wavelength division multiplexer is connected to the second output of the first coupler, and the output of the second wavelength division multiplexer is connected to the first end of the third gain fiber.

8. The wavelength tunable single frequency fiber laser of claim 7, wherein, The fiber amplifier further includes a third isolator, a second coupler, and a photodetector. The input end of the third isolator is connected to the second end of the third gain fiber, the output end of the third isolator is connected to the input end of the second coupler, the first output end of the second coupler is used to output the amplified single-frequency laser, and the second output end of the second coupler is connected to the photodetector.

9. The wavelength tunable single frequency fiber laser of claim 7, wherein, Both the first pump source and the second pump source include a 976nm semiconductor laser, and the first gain fiber, the second gain fiber and the third gain fiber all include ytterbium-doped fiber.

10. The wavelength tunable single frequency fiber laser of claim 9, wherein, The single-frequency fiber laser has an output wavelength range of 1030nm to 1093nm.

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