CN116667114A - 2090nm linear polarization full polarization-preserving single-frequency fiber laser based on dynamic grating in gain fiber - Google Patents

2090nm linear polarization full polarization-preserving single-frequency fiber laser based on dynamic grating in gain fiber Download PDF

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CN116667114A
CN116667114A CN202310549308.0A CN202310549308A CN116667114A CN 116667114 A CN116667114 A CN 116667114A CN 202310549308 A CN202310549308 A CN 202310549308A CN 116667114 A CN116667114 A CN 116667114A
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fiber
optical fiber
polarization
holmium
gain
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姚宝权
魏迪生
戴通宇
唐锦文
李俊辉
华笑笑
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Harbin Institute of Technology
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Harbin Institute of Technology
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/05—Construction or shape of optical resonators; Accommodation of active medium therein; Shape of active medium
    • H01S3/06—Construction or shape of active medium
    • H01S3/063—Waveguide lasers, i.e. whereby the dimensions of the waveguide are of the order of the light wavelength
    • H01S3/067—Fibre lasers
    • H01S3/06754—Fibre amplifiers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/05—Construction or shape of optical resonators; Accommodation of active medium therein; Shape of active medium
    • H01S3/06—Construction or shape of active medium
    • H01S3/063—Waveguide lasers, i.e. whereby the dimensions of the waveguide are of the order of the light wavelength
    • H01S3/067—Fibre lasers
    • H01S3/0675—Resonators including a grating structure, e.g. distributed Bragg reflectors [DBR] or distributed feedback [DFB] fibre lasers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/05—Construction or shape of optical resonators; Accommodation of active medium therein; Shape of active medium
    • H01S3/06—Construction or shape of active medium
    • H01S3/063—Waveguide lasers, i.e. whereby the dimensions of the waveguide are of the order of the light wavelength
    • H01S3/067—Fibre lasers
    • H01S3/06791—Fibre ring lasers
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
    • Y02A90/00—Technologies having an indirect contribution to adaptation to climate change
    • Y02A90/10—Information and communication technologies [ICT] supporting adaptation to climate change, e.g. for weather forecasting or climate simulation

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  • Electromagnetism (AREA)
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Abstract

The invention discloses a 2090nm linear polarization full polarization-preserving single-frequency fiber laser based on a dynamic grating in a gain fiber, belongs to the technical field of fiber lasers, and aims to solve the problems of the conventional method for realizing the single-frequency fiber laser. The invention comprises a ring cavity single-frequency optical fiber oscillator and an optical fiber amplifier; the optical fiber amplifier is used for amplifying linear polarized laser output by the annular cavity single-frequency optical fiber oscillator; the annular cavity single-frequency optical fiber oscillator comprises a first thulium optical fiber oscillator, a first wavelength division multiplexer, a first single-mode polarization-preserving holmium-doped gain optical fiber, a first optical fiber circulator, a second polarization-preserving holmium-doped gain optical fiber, a high-reflectivity optical fiber Bragg grating, an output coupler, a second optical fiber circulator and an optical fiber isolator; the optical fiber amplifier comprises a second thulium optical fiber oscillator, a second wavelength division multiplexer, a third polarization-preserving holmium-doped gain optical fiber and a band-pass filter; the laser adopts a full polarization maintaining structure, all devices in the laser are polarization maintaining devices, and horizontal shaft fusion of the devices is adopted.

Description

2090nm linear polarization full polarization-preserving single-frequency fiber laser based on dynamic grating in gain fiber
Technical Field
The invention relates to a stability technology of 2090nm linear polarization full polarization single-frequency optical fiber laser in single-frequency operation, and belongs to the technical field of optical fiber lasers.
Background
The 2 mu m wave band laser is positioned in the transparent area of the atmospheric window and is also positioned in the eye safety wave band, and the damage threshold value of the 2 mu m wave band laser to the eyes is 4 orders of magnitude larger than that of the 1 mu m wave band laser, so that the 2 mu m coherent laser is very suitable for the fields of space optical communication, laser radar, laser remote sensing and the like. At present, researches on single-frequency fiber lasers with the wave band of 2 mu m are mainly focused in a high-gain range of 1900-2050nm, and most thulium-doped fibers are used as gain media of the lasers, so that single-frequency laser output with the wave band approaching to 2.1 mu m or even higher is difficult to realize. The gain bandwidth of the holmium doped fiber can be covered from 1.9 μm to over 2.1 μm, and the thulium doped fiber laser with the output wavelength of 1940-1950 nm can be used for in-band pumping, so that the advantage of high pumping quantum efficiency is achieved. In addition, 2090nm is just near the strong emission peak of Ho-YAG crystal, and the single-mode full polarization-maintaining fiber laser has the characteristics of good beam quality and stable performance, so that the stable and reliable 2090nm linear polarization full polarization-maintaining single-frequency fiber laser can be used as an ideal seed source of a narrow-linewidth Ho-YAG amplifier.
In addition, common methods for implementing single frequency fiber lasers include ultra-short cavity methods, cascaded subchamber methods, or saturable absorber methods. Although the ultra-short cavity method can realize more stable single-frequency laser output, the shorter active fiber length limits the increase of laser output power. The high-definition subchamber or the saturable absorber method is mostly used in the optical fiber oscillator with the annular cavity structure, and the longer cavity length can accommodate rich wavelength selection modes. The provision of multiple subchambers in the annular cavity not only increases the complexity of the resonant cavity, but also makes the stability of the laser during single frequency operation a significant challenge.
Disclosure of Invention
Aiming at the problems of the conventional method for realizing the single-frequency fiber laser, the invention provides a 2090nm linear polarization full polarization single-frequency fiber laser based on a dynamic grating in a gain fiber.
The 2090nm linear polarization full polarization single-frequency optical fiber laser based on the dynamic grating in the gain optical fiber comprises an annular cavity single-frequency optical fiber oscillator and an optical fiber amplifier; the optical fiber amplifier is used for amplifying linear polarized laser output by the annular cavity single-frequency optical fiber oscillator;
the annular cavity single-frequency optical fiber oscillator comprises a first thulium optical fiber oscillator 1-1, a first wavelength division multiplexer 2-1, a first single-mode polarization-preserving holmium-doped gain optical fiber 3-1, a first optical fiber circulator 4-1, a second polarization-preserving holmium-doped gain optical fiber 3-2, a high-reflectivity optical fiber Bragg grating 5, an output coupler 6, a second optical fiber circulator 4-2 and an optical fiber isolator 7;
the optical fiber amplifier comprises a second thulium optical fiber oscillator 1-2, a second wavelength division multiplexer 2-2, a third polarization-preserving holmium-doped gain optical fiber 3-3 and a band-pass filter 8;
the first thulium fiber oscillator 1-1 is connected with the pumping input end of the first wavelength division multiplexer 2-1, and the output end of the first wavelength division multiplexer 2-1 is connected with one end of the first single-mode polarization-preserving holmium-doped gain fiber 3-1; the other end of the first single-mode polarization-maintaining holmium-doped gain optical fiber 3-1 is connected with a first port of a first optical fiber circulator 4-1; the second port of the first optical fiber circulator 4-1 is connected with one end of a second single-mode polarization-preserving holmium-doped gain optical fiber 3-2, and the other end of the unpumped second single-mode polarization-preserving holmium-doped gain optical fiber 3-2 is connected with a high-reflectivity optical fiber Bragg grating 5; the third port of the first optical fiber circulator 4-1 is connected with the input end of the output coupler 6, the first output port of the output coupler 6 is connected with the first port of the second optical fiber circulator 4-2, and the second port of the second optical fiber circulator 4-2 is connected with the laser input end of the first wavelength division multiplexer 2-1;
the second output port of the output coupler 6 is connected with the input end of the optical fiber isolator 7, and the output end of the optical fiber isolator 7 is connected with the laser input end of the second wavelength division multiplexer 2-2;
the second thulium fiber oscillator 1-2 is connected with the pumping input end of the second wavelength division multiplexer 2-2, the output end of the second wavelength division multiplexer 2-2 is connected with one end of a third single-mode polarization-preserving holmium-doped gain fiber 3-3, and the other end of the third single-mode polarization-preserving holmium-doped gain fiber 3-3 is connected with a band-pass filter 8;
the laser adopts a full polarization maintaining structure, all devices in the laser are polarization maintaining devices, and horizontal shaft fusion of the devices is adopted.
Preferably, the first optical fiber circulator 4-1, the second optical fiber circulator 4-2, the output coupler 6 and the optical fiber isolator 7 all operate with a single axis;
the polarization isolation of the optical fiber isolator 7 is more than 25dB, the insertion loss is less than 1.5dB, the highest bearing average power is 1W, and the type of the tail fiber is PM-GDF-10/130-2000;
the single-axis working device and other polarization maintaining devices of the laser jointly realize the linear polarized light output of the annular cavity single-frequency optical fiber oscillator.
Preferably, the dynamic grating formed in the second polarization-maintaining holmium-doped fiber 3-2 is used for constructing an ultra-narrow band-pass filter, and the ultra-narrow band-pass filter is used for narrow-band filtering and reflection wavelength self-adaption of the self-writing fiber grating induced by standing wave saturation absorption so as to inhibit generation of a mode jump and a side mode of the annular cavity single-frequency fiber oscillator and realize stable output of single-frequency laser.
Preferably, the laser wavelength 1940 nm+ -1 nm of the first thulium fiber oscillator 1-1 and the second thulium fiber oscillator 1-2 has a maximum output power of 5W.
Preferably, the signal light transmission loss of the first wavelength division multiplexer 2-1 and the second wavelength division multiplexer 2-2 is <1.1dB, the pump transmission loss is <2dB, the polarization extinction ratio is >20dB, the type of the tail fiber is PM-GDF-10/130-2000, the highest bearing pump power is 10W, and the signal light power is 1W; the double shaft works.
Preferably, the first single-mode polarization-maintaining holmium-doped gain fiber 3-1 is a polarization-maintaining holmium-doped fiber PM-HDF-10/130-15FA, the diameter of a fiber core/cladding is 10/130 μm, the numerical apertures of the fiber core and the cladding are 0.15 and 0.46 respectively, the absorption coefficient of the fiber core is about 58dB/m@1950nm, and the length is 3m;
the second single-mode polarization-maintaining holmium-doped gain optical fiber 3-2 is a polarization-maintaining holmium-doped optical fiber IXF-HDF-PM-8-125, the diameter of a fiber core/cladding is 8/125 mu m, the numerical aperture of the fiber core is 0.15, the absorption coefficient of the fiber core is about 58dB/m@1950nm, and the lengths are 0.55m and 0.8m respectively;
the third single-mode polarization-preserving holmium-doped gain fiber 3-3 is a polarization-preserving holmium-doped fiber PM-HDF-10/130-15FA, the diameter of a fiber core/cladding is 10/130 mu m, the numerical apertures of the fiber core and the cladding are 0.15 and 0.46 respectively, the absorption coefficient of the fiber core is about 58dB/m@1950nm, and the length is 3m.
Preferably, the first optical fiber circulator 4-1 and the second optical fiber circulator 4-2 have the same structure, the insertion loss from the first port to the second port of the optical fiber circulator is <1.5dB, the polarization extinction ratio is >24dB, and the isolation from the second port to the first port is >20dB; the insertion loss from the second port to the third port is <1.5dB, the polarization extinction ratio is >24dB, the isolation from the third port to the second port is >25dB, and the type of the tail fiber is PM1950; the slow axis works and the fast axis is cut off.
Preferably, the center wavelength of the high-reflectivity fiber Bragg grating 5 is 2090nm plus or minus 1nm, the peak reflectivity is >99%, the transmission bandwidth is 2nm plus or minus 0.1nm, the sustainable pumping power is higher than 50W spectrum side mode rejection ratio and is more than 20dB, and the type of the tail fiber is PM-GDF-10/130-2000; the double shaft works.
Preferably, the transmittance from the input end to the first output end of the output coupler 6 is 30%, the transmittance from the input end to the second output end is 70%, the insertion loss of 2090nm signal light is 2.7dB, the highest average power is 1W, and the type of pigtail is PM1950; the slow axis works and the fast axis is cut off.
Preferably, the center wavelength of the band-pass filter 8 is 2090nm, the minimum pass bandwidth is +/-20 nm, the cut-off bandwidth is 2030-2070&2110-2150nm, the insertion loss is <1dB, and the type of the tail fiber is PM1950; the double shaft works.
The invention has the beneficial effects that:
1. the 2090nm linear polarization full polarization maintaining optical fiber single-frequency laser based on the dynamic grating in the gain optical fiber is provided, and the annular cavity single-frequency oscillator of the laser uses a thulium doped pumping source, a wavelength division multiplexer, a holmium doped optical fiber, an circulator, a high-reflectivity Bragg grating and an output coupler, so that stable single-frequency laser output of 50mW is realized at the maximum of 2090nm wave band.
2. The laser uses a full polarization-preserving structure, adopts a plurality of devices working in a single axis (slow axis working and fast axis cutting off), realizes linearly polarized light output, and has reliable long-term stability. The polarization extinction ratio of the oscillator and the amplifier was measured to be greater than 17dB by using 2090nm half wave plate, grazing prism.
3. The multi-ring device is used in the annular cavity, so that the unidirectional operation of laser in the cavity is ensured, and the space hole burning effect is eliminated. No optical power is detected at the inverting output port of the output coupler.
4. The narrow-band filtering characteristic and the reflection wavelength self-adaption characteristic of the self-writing fiber bragg grating are induced by using standing wave saturated absorption in the unpumped holmium-doped fiber, so that the generation of mode hops and side modes is effectively inhibited, and stable and reliable single-frequency laser output is realized.
5. The coupling ratio of the output coupler is reasonably optimized, gain competition is effectively restrained, and the efficiency of the oscillator is optimized.
6. The length of the unpumped holmium-doped optical fiber is reasonably optimized, and parameters required by experiments are simulated, so that a good filtering effect is achieved.
7. The Power of 2090nm single-frequency laser is effectively amplified by using a Master-Oscillator Power-Amplifier (MOPA) laser system, and the output Power of the Amplifier reaches 1W.
Drawings
Fig. 1 is a schematic structural diagram of a 2090nm linear polarization full polarization maintaining fiber single-frequency laser based on a dynamic grating in a gain fiber according to the present invention;
FIG. 2 is a wavelength chart of a 2090nm linear polarization full polarization maintaining fiber single frequency laser based on dynamic gratings in gain fibers of example 1;
FIG. 3 is a graph showing the variation of the output power of the fiber ring cavity oscillator of the 2090nm linear polarization full polarization maintaining fiber single frequency laser based on the dynamic grating in the gain fiber according to the embodiment 1 with the pump power;
FIG. 4 is a graph showing the variation of the output power of the fiber amplifier of the 2090nm linear polarization full polarization maintaining fiber single frequency laser based on the dynamic grating in the gain fiber according to the embodiment 1;
FIG. 5 is a transmission curve of the injection scanning confocal F-P cavity of the 2090nm linear polarization full polarization maintaining fiber single frequency laser of example 1 based on the dynamic grating in the gain fiber;
fig. 6 is a graph of a spectrum around 200MHz for a 2090nm linear polarization fully polarization maintaining fiber single frequency laser based on dynamic gratings in gain fibers and a lorentz fitted curve for example 1.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
It should be noted that, without conflict, the embodiments of the present invention and features of the embodiments may be combined with each other.
The invention is further described below with reference to the drawings and specific examples, which are not intended to be limiting.
The first embodiment is as follows: the following describes, with reference to fig. 1 to 6, a 2090nm linear polarization full polarization single-frequency optical fiber laser based on a dynamic grating in a gain optical fiber according to the present embodiment, where the laser according to the present embodiment uses a full polarization maintaining structure, and adopts a plurality of devices that operate in a single axis (slow axis operation, fast axis cutoff), so as to achieve linear polarized light output, and long-term stability is reliable. The multi-ring device is used in the annular cavity, so that the unidirectional operation of laser in the cavity is ensured, and the space hole burning effect is eliminated. No optical power is detected at the inverting output port of the output coupler. The narrow-band filtering characteristic and the reflection wavelength self-adaption characteristic of the self-writing fiber bragg grating are induced by using standing wave saturated absorption in the unpumped holmium-doped fiber, so that the generation of mode hops and side modes is effectively inhibited, and stable and reliable single-frequency laser output is realized. The coupling ratio of the output coupler is reasonably optimized, gain competition is effectively restrained, and the efficiency of the oscillator is optimized. The length of the unpumped holmium-doped optical fiber is reasonably optimized, and parameters required by experiments are simulated, so that a good filtering effect is achieved.
The following describes a specific example.
Example 1:
the 2090nm linear polarization full polarization single-frequency optical fiber laser based on the dynamic grating in the gain optical fiber comprises an annular cavity single-frequency optical fiber oscillator and an optical fiber amplifier; the optical fiber amplifier is used for amplifying linear polarized laser output by the annular cavity single-frequency optical fiber oscillator;
the annular cavity single-frequency optical fiber oscillator comprises a first thulium optical fiber oscillator 1-1, a first wavelength division multiplexer 2-1, a first single-mode polarization-preserving holmium-doped gain optical fiber 3-1, a first optical fiber circulator 4-1, a second single-mode polarization-preserving holmium-doped gain optical fiber 3-2, a high-reflectivity optical fiber Bragg grating 5, an output coupler 6, a second optical fiber circulator 4-2 and an optical fiber isolator 7;
the optical fiber amplifier comprises a second thulium optical fiber oscillator 1-2, a second wavelength division multiplexer 2-2, a third single-mode polarization-preserving holmium-doped gain optical fiber 3-3 and a band-pass filter 8;
the first thulium fiber oscillator 1-1 is connected with the pumping input end of the first wavelength division multiplexer 2-1, and the output end of the first wavelength division multiplexer 2-1 is connected with one end of the first single-mode polarization-preserving holmium-doped gain fiber 3-1; the other end of the first single-mode polarization-maintaining holmium-doped gain optical fiber 3-1 is connected with a first port of a first optical fiber circulator 4-1; the second port of the first optical fiber circulator 4-1 is connected with one end of a second single-mode polarization-preserving holmium-doped gain optical fiber 3-2, and the other end of the unpumped second single-mode polarization-preserving holmium-doped gain optical fiber 3-2 is connected with a high-reflectivity optical fiber Bragg grating 5; the third port of the first optical fiber circulator 4-1 is connected with the input end of the output coupler 6, the first output port of the output coupler 6 is connected with the first port of the second optical fiber circulator 4-2, and the second port of the second optical fiber circulator 4-2 is connected with the laser input end of the first wavelength division multiplexer 2-1;
the second output port of the output coupler 6 is connected with the input end of the optical fiber isolator 7, and the output end of the optical fiber isolator 7 is connected with the laser input end of the second wavelength division multiplexer 2-2;
the second thulium fiber oscillator 1-2 is connected with the pumping input end of the second wavelength division multiplexer 2-2, the output end of the second wavelength division multiplexer 2-2 is connected with one end of a third single-mode polarization-preserving holmium-doped gain fiber 3-3, and the other end of the third single-mode polarization-preserving holmium-doped gain fiber 3-3 is connected with a band-pass filter 8;
the laser adopts a full polarization maintaining structure, all devices in the laser are polarization maintaining devices, and horizontal shaft fusion of the devices is adopted.
The first optical fiber circulator 4-1, the second optical fiber circulator 4-2, the output coupler 6 and the optical fiber isolator 7 all work in a single axis;
the polarization isolation of the optical fiber isolator 7 is more than 25dB, the insertion loss is less than 1.5dB, the highest bearing average power is 1W, and the type of the tail fiber is PM-GDF-10/130-2000;
the device of single-axis operation (slow axis operation, fast axis cut-off) and other polarization-preserving devices of the laser jointly realize the linear polarized light output of the annular cavity single-frequency optical fiber oscillator.
The dynamic grating formed in the second polarization-preserving holmium-doped optical fiber 3-2 is used for constructing an ultra-narrow band-pass filter, and the ultra-narrow band-pass filter is used for narrow-band filtering and reflection wavelength self-adaption of the self-writing optical fiber grating induced by standing wave saturation absorption so as to inhibit the generation of a mode jump and a side mode of the annular cavity single-frequency optical fiber oscillator and realize single-frequency laser stable output.
The laser wavelength 1940nm plus or minus 1nm of the first thulium optical fiber oscillator 1-1 and the second thulium optical fiber oscillator 1-2 is 5W.
The signal light transmission loss of the first wavelength division multiplexer 2-1 and the second wavelength division multiplexer 2-2 is <1.1dB, the pumping transmission loss is <2dB, the polarization extinction ratio is >20dB, the type of the tail fiber is PM-GDF-10/130-2000, the highest bearing pumping power is 10W, and the signal light power is 1W; the double shaft works.
The first single-mode polarization-maintaining holmium-doped gain fiber 3-1 is a polarization-maintaining holmium-doped single-cladding fiber PM-HDF-10/130-15FA, the diameter of a fiber core/cladding is 10/130 mu m, the numerical apertures of the fiber core and the cladding are 0.15 and 0.46 respectively, the absorption coefficient of the fiber core is about 58dB/m@1950nm, and the length is 3m;
the second single-mode polarization-maintaining holmium-doped gain fiber 3-2 is a polarization-maintaining holmium-doped single-clad fiber IXF-HDF-PM-8-125, the diameter of a fiber core/clad is 8/125 mu m, the numerical aperture of the fiber core is 0.15, the absorption coefficient of the fiber core is about 58dB/m@1950nm, and the lengths of the fiber core and the cladding are 0.55m and 0.8m respectively;
the third single-mode polarization-preserving holmium-doped gain fiber 3-3 is a polarization-preserving holmium-doped single-cladding fiber PM-HDF-10/130-15FA, the diameter of a fiber core/cladding is 10/130 mu m, the numerical apertures of the fiber core and the cladding are 0.15 and 0.46 respectively, the absorption coefficient of the fiber core is about 58dB/m@1950nm, and the length is 3m.
The first optical fiber circulator 4-1 and the second optical fiber circulator 4-2 have the same structure, the insertion loss from the first port to the second port of the optical fiber circulator is <1.5dB, the polarization extinction ratio is >24dB, and the isolation from the second port to the first port is >20dB; the insertion loss from the second port to the third port is <1.5dB, the polarization extinction ratio is >24dB, the isolation from the third port to the second port is >25dB, and the type of the tail fiber is PM1950; the slow axis works and the fast axis is cut off.
The center wavelength of the high-reflectivity fiber Bragg grating 5 is 2090nm plus or minus 1nm, the peak reflectivity is more than 99%, the transmission bandwidth is 2nm plus or minus 0.1nm, the bearable pumping power is higher than 50W, the spectral side mode suppression ratio is more than 20dB, and the type of the tail fiber is PM-GDF-10/130-2000; the double shaft works.
The transmittance of the input end of the output coupler 6 to the first output end is 30%, the transmittance of the input end to the second output end is 70%, the insertion loss of 2090nm signal light is 2.7dB, the highest bearing average power is 1W, and the type of tail fiber is PM1950; the slow axis works and the fast axis is cut off.
The center wavelength of the band-pass filter 8 is 2090nm, the minimum pass bandwidth is +/-20 nm, the cut-off bandwidth is 2030-2070&2110-2150nm, the insertion loss is less than 1dB, and the type of the tail fiber is PM1950; the double shaft works.
The working process comprises the following steps: the pump beam generated by the first thulium-doped pump source (the first thulium optical fiber oscillator 1-1) is injected into the first single-mode polarization-preserving holmium-doped gain optical fiber 3-1 through the pump fiber of the first wavelength division multiplexer 2-1, so as to provide gain for the annular cavity single-frequency optical fiber oscillator and realize particle number inversion. The ring cavity single-frequency optical fiber oscillator is used for generating an oscillating laser beam, the first optical fiber circulator 4-1 and the second optical fiber circulator 4-2 ensure the unidirectional operation of the beam, and the gain hole burning phenomenon in the first single-mode polarization-maintaining holmium-doped gain optical fiber 3-1 is effectively eliminated. The oscillation laser beam passes back and forth through the linear part of the annular cavity single-frequency optical fiber oscillator, comprises an unpumped second single-mode polarization-preserving holmium-doped optical fiber 3-2 and a 2090nm high-reflectivity Bragg grating 5, forms a dynamic grating with narrow-band filtering in the second single-mode polarization-preserving holmium-doped gain optical fiber 3-2 through the standing wave effect, and effectively inhibits the generation of mode hops and side modes. And finally outputting stable narrow linewidth single-frequency laser through an output coupler 6. The single-frequency laser is used as a seed beam of the optical fiber amplifier, is injected into the optical fiber amplifier through a signal fiber of the second wavelength division multiplexer 2-2, and is effectively amplified in a third single-mode polarization-preserving holmium-doped gain optical fiber 3-3 pumped by a second thulium-doped pumping source (a second thulium optical fiber oscillator 1-2), so that 2090nm single-frequency laser beam output of watt magnitude is realized.
In this embodiment, each device is welded horizontally by an opposite axis, that is, the slow axis of the pigtail corresponds to the slow axis, and the fast axis corresponds to the fast axis.
FIG. 2 is a wavelength chart of a 2090nm linear polarization full polarization maintaining single frequency fiber laser based on dynamic gratings in gain fibers of example 1; as can be seen, the laser wavelength is around 2090nm during single frequency stable operation.
FIG. 3 is a graph showing the variation of the output power of the ring cavity single frequency fiber oscillator of the 2090nm linear polarization full polarization maintaining single frequency fiber laser based on the dynamic grating in the gain fiber according to the embodiment 1; as can be seen from the graph, when the length of the second polarization-maintaining holmium-doped optical fiber is 0.55m, the output coupler adopts 70% coupling ratio as output proportion, and the maximum stable single-frequency output power of the annular cavity single-frequency optical fiber oscillator is approximately 31mW; when the length of the second polarization-maintaining holmium-doped optical fiber is 0.55m, the output coupler adopts a coupling ratio of 30% as an output proportion, and the maximum stable single-frequency output power of the annular cavity optical fiber oscillator is 14.4mW; when the length of the second polarization-maintaining holmium-doped optical fiber is 0.8m, the output coupler adopts a coupling ratio of 30% as an output proportion, and the maximum stable single-frequency output power of the optical fiber ring cavity oscillator is 29mW; when the length of the second polarization-maintaining holmium-doped optical fiber is 0.8m, the output coupler adopts 70% coupling ratio as output proportion, and the maximum stable single-frequency output power of the optical fiber ring cavity oscillator is 53.5mW.
FIG. 4 is a graph showing the variation of the output power of the fiber amplifier of the 2090nm linear polarization full polarization single frequency fiber laser according to the dynamic grating in the gain fiber according to the embodiment 1; as can be seen from the graph, when the seed optical power is 53.5mW injected into the optical fiber amplifier, the maximum output power of the amplifier is limited by the pump power and is 1W; the seed light injection optical fiber amplifiers with other power levels realize the output power of more than 600 mW; no significant ASE was observed in the spectrum.
FIG. 5 is a transmission curve of the injection scanning confocal F-P cavity of the 2090nm linear polarization full polarization single frequency fiber laser of example 1 based on the dynamic grating in the gain fiber; as can be seen, the laser is in a single frequency state.
FIG. 6 is a graph of a spectrum around 200MHz for a 2090nm linear polarization full polarization maintaining single frequency fiber laser based on dynamic gratings in gain fibers of example 1, fitted by Lorentz; as can be seen, the measured 20dB linewidth of the fiber laser was 20.6KHz.
The second embodiment is as follows: the first difference between this embodiment and the specific embodiment is that: the output wavelength power of the first thulium fiber oscillator 1-1 and the second thulium fiber oscillator 1-2 is not limited to 1940nm or 1950nm, and any wavelength within the effective absorption cross section range of the polarization-preserving holmium-doped fiber can be used. The other is the same as in the first embodiment.
And a third specific embodiment: the present embodiment is different from one of the first to second embodiments in that: the preferred power splitting ratio of the output coupler 6 is 10:90, 40:60 or 50:50. The other is the same as in the first embodiment.
The specific embodiment IV is as follows: the present embodiment is different from one to three embodiments in that: the length of the second polarization-maintaining holmium-doped gain optical fiber 3-2 is 0.3-1.3 m, and the specification of the optical fiber is not limited to IXF-HDF-PM-8-125 or PM-HDF-10/130-15FA. The other embodiments are the same as those of the first to third embodiments.
Fifth embodiment: the present embodiment differs from the first to fourth embodiments in that: the center wavelength of the high-reflectivity bragg grating 5 is not limited to 2090nm, and can be any wavelength within the effective emission section of the holmium-doped gain fiber. The other embodiments are the same as those of the first to fourth embodiments.
Although the invention herein has been described with reference to particular embodiments, it is to be understood that these embodiments are merely illustrative of the principles and applications of the present invention. It is therefore to be understood that numerous modifications may be made to the illustrative embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention as defined by the appended claims. It should be understood that the different dependent claims and the features described herein may be combined in ways other than as described in the original claims. It is also to be understood that features described in connection with separate embodiments may be used in other described embodiments.

Claims (10)

1. The 2090nm linear polarization full polarization-maintaining single-frequency fiber laser based on the dynamic grating in the gain fiber is characterized by comprising a ring cavity single-frequency fiber oscillator and a fiber amplifier; the optical fiber amplifier is used for amplifying linear polarized laser output by the annular cavity single-frequency optical fiber oscillator;
the annular cavity single-frequency optical fiber oscillator comprises a first thulium optical fiber oscillator (1-1), a first wavelength division multiplexer (2-1), a first single-mode polarization-preserving holmium-doped gain optical fiber (3-1), a first optical fiber circulator (4-1), a second single-mode polarization-preserving holmium-doped gain optical fiber (3-2), a high-reflectivity optical fiber Bragg grating (5), an output coupler (6), a second optical fiber circulator (4-2) and an optical fiber isolator (7);
the optical fiber amplifier comprises a second thulium optical fiber oscillator (1-2), a second wavelength division multiplexer (2-2), a third single-mode polarization-preserving holmium-doped gain optical fiber (3-3) and a band-pass filter (8);
the first thulium fiber oscillator (1-1) is connected with the pumping input end of the first wavelength division multiplexer (2-1), and the output end of the first wavelength division multiplexer (2-1) is connected with one end of the first single-mode polarization-maintaining holmium-doped gain fiber (3-1); the other end of the first single-mode polarization-maintaining holmium-doped gain optical fiber (3-1) is connected with a first port of a first optical fiber circulator (4-1); the second port of the first optical fiber circulator (4-1) is connected with one end of a second single-mode polarization-preserving holmium-doped gain optical fiber (3-2), and the other end of the unpumped second single-mode polarization-preserving holmium-doped gain optical fiber (3-2) is connected with a high-reflectivity optical fiber Bragg grating (5); the third port of the first optical fiber circulator (4-1) is connected with the input end of the output coupler (6), the first output port of the output coupler (6) is connected with the first port of the second optical fiber circulator (4-2), and the second port of the second optical fiber circulator (4-2) is connected with the laser input end of the first wavelength division multiplexer (2-1);
the second output port of the output coupler (6) is connected with the input end of the optical fiber isolator (7), and the output end of the optical fiber isolator (7) is connected with the laser input end of the second wavelength division multiplexer (2-2);
the second thulium fiber oscillator (1-2) is connected with the pumping input end of the second wavelength division multiplexer (2-2), the output end of the second wavelength division multiplexer (2-2) is connected with one end of a third single-mode polarization-preserving holmium-doped gain fiber (3-3), and the other end of the third single-mode polarization-preserving holmium-doped gain fiber (3-3) is connected with a band-pass filter (8);
the laser adopts a full polarization maintaining structure, all devices in the laser are polarization maintaining devices, and horizontal shaft fusion of the devices is adopted.
2. The 2090nm linear polarization full polarization single frequency fiber laser based on dynamic grating in gain fiber according to claim 1, wherein the first fiber circulator (4-1), the second fiber circulator (4-2), the output coupler (6) and the fiber isolator (7) all work with single axis;
the polarization isolation of the optical fiber isolator (7) is more than 25dB, the insertion loss is less than 1.5dB, the highest bearing average power is 1W, and the type of the tail fiber is PM-GDF-10/130-2000;
the single-axis working device and other polarization maintaining devices of the laser jointly realize the linear polarized light output of the annular cavity single-frequency optical fiber oscillator.
3. The 2090nm linear polarization full polarization single frequency fiber laser based on the dynamic grating in the gain fiber according to claim 1, wherein the dynamic grating formed in the second single mode polarization holmium-doped fiber (3-2) is used for constructing an ultra-narrow band-pass filter, and the ultra-narrow band-pass filter is used for narrow band filtering and reflection wavelength self-adaption of the self-writing fiber grating induced by standing wave saturated absorption so as to inhibit generation of a ring cavity single frequency fiber oscillator mode-skipping and a side mode, and realize single frequency laser stable output.
4. The 2090nm linear polarization full polarization single frequency fiber laser based on dynamic grating in gain fiber according to claim 1, wherein the laser wavelength 1940nm + -1 nm of the first thulium fiber oscillator (1-1) and the second thulium fiber oscillator (1-2) has a maximum output power of 5W.
5. The 2090nm linear polarization full polarization single frequency fiber laser based on dynamic grating in gain fiber according to claim 1, characterized in that the signal light transmission loss of the first wavelength division multiplexer (2-1) and the second wavelength division multiplexer (2-2) is <1.1dB, the pump transmission loss is <2dB, the polarization extinction ratio is >20dB, the type of the used pigtail is PM-GDF-10/130-2000, the highest bearing pump power is 10W, and the signal light power is 1W; the double shaft works.
6. The 2090nm linear polarization full polarization single frequency fiber laser based on dynamic grating in gain fiber according to claim 1, wherein the first single mode polarization-preserving holmium-doped gain fiber (3-1) is polarization-preserving holmium-doped fiber PM-HDF-10/130-15FA, the diameter of the fiber core/cladding is 10/130 μm, the numerical aperture of the fiber core and the cladding is 0.15 and 0.46, respectively, the absorption coefficient of the fiber core is about 58dB/m@1950nm, and the length is 3m;
the second single-mode polarization-preserving holmium-doped gain optical fiber (3-2) is a polarization-preserving holmium-doped optical fiber IXF-HDF-PM-8-125, the diameter of a fiber core/cladding is 8/125 mu m, the numerical aperture of the fiber core is 0.15, the absorption coefficient of the fiber core is about 58dB/m@1950nm, and the lengths of the fiber core and the fiber core are 0.55m and 0.8m respectively;
the third single-mode polarization-preserving holmium-doped gain fiber (3-3) is a polarization-preserving holmium-doped fiber PM-HDF-10/130-15FA, the diameter of a fiber core/cladding is 10/130 mu m, the numerical apertures of the fiber core and the cladding are 0.15 and 0.46 respectively, the absorption coefficient of the fiber core is about 58dB/m@1950nm, and the length is 3m.
7. The 2090nm linear polarization full polarization single frequency fiber laser based on dynamic grating in gain fiber according to claim 1, wherein the first fiber circulator (4-1) and the second fiber circulator (4-2) have the same structure, the insertion loss from the first port to the second port of the fiber circulator is <1.5dB, the polarization extinction ratio is >24dB, and the isolation from the second port to the first port is >20dB; the insertion loss from the second port to the third port is <1.5dB, the polarization extinction ratio is >24dB, the isolation from the third port to the second port is >25dB, and the type of the tail fiber is PM1950; the slow axis works and the fast axis is cut off.
8. The 2090nm linear polarization full polarization single frequency fiber laser based on dynamic grating in gain fiber according to claim 1, characterized in that the center wavelength of the high reflectivity fiber bragg grating (5) is 2090nm + -1 nm, the peak reflectivity is >99%, the transmission bandwidth is 2nm + -0.1 nm, the sustainable pumping power is higher than 50W spectral side mode suppression ratio >20dB, and the type of pigtail is PM-GDF-10/130-2000; the double shaft works.
9. The 2090nm linear polarization full polarization single frequency fiber laser based on the dynamic grating in the gain fiber according to claim 1, wherein the transmittance from the input end to the first output end of the output coupler (6) is 30%, the transmittance from the input end to the second output end is 70%, the insertion loss of 2090nm signal light is 2.7dB, the highest average power bearing is 1W, and the type of pigtail is PM1950; the slow axis works and the fast axis is cut off.
10. The 2090nm linear polarization full polarization single frequency fiber laser based on dynamic grating in gain fiber according to claim 1, characterized in that the center wavelength of the band-pass filter (8) is 2090nm, the minimum pass bandwidth is + -20 nm, the cut-off bandwidth is 2030-2070&2110-2150nm, the insertion loss is <1dB, and the type of pigtail is PM1950; the double shaft works.
CN202310549308.0A 2023-05-16 2023-05-16 2090nm linear polarization full polarization-preserving single-frequency fiber laser based on dynamic grating in gain fiber Pending CN116667114A (en)

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