CN117613677A - High-order mode nanosecond green laser - Google Patents
High-order mode nanosecond green laser Download PDFInfo
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- 238000005253 cladding Methods 0.000 claims description 49
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- H—ELECTRICITY
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- 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
- H01S5/00—Semiconductor lasers
- H01S5/50—Amplifier structures not provided for in groups H01S5/02 - H01S5/30
- H01S5/5027—Concatenated amplifiers, i.e. amplifiers in series or cascaded
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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
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- H01S3/063—Waveguide lasers, i.e. whereby the dimensions of the waveguide are of the order of the light wavelength
- H01S3/067—Fibre lasers
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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
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Abstract
The invention belongs to the technical field of lasers, and particularly relates to a high-order mode nanosecond green laser. The semiconductor laser device comprises a semiconductor laser device for generating nanosecond seed laser, wherein the semiconductor laser device is connected with a fiber band-pass filter isolator through fiber fusion: the optical fiber band-pass filter isolator is sequentially connected with a power amplifier and a frequency multiplication optical path through optical fiber fusion, the power amplifier comprises a primary single-mode amplifier, a secondary multi-mode amplifier and a tertiary multi-mode amplifier, the primary single-mode amplifier is a first single-mode polarization-preserving ytterbium-doped optical fiber amplifier of forward pumping or backward pumping, and the secondary multi-mode amplifier is a second multi-mode polarization-preserving ytterbium-doped optical fiber amplifier of unidirectional pumping or bidirectional pumping; the three-stage multimode amplifier is a third multimode polarization-preserving ytterbium-doped fiber amplifier of unidirectional pumping or bidirectional pumping. The invention adopts the all-fiber structure to realize the output of the fundamental frequency light of the high-order mode, and has more compact structure and lower power consumption.
Description
Technical Field
The invention belongs to the technical field of lasers, and particularly relates to a high-order mode nanosecond green laser.
Background
At present, the laser of the green light wave band has wide application in the fields of medical treatment, precision machining, marine communication and the like. Firstly, green light can be used as a pumping source of ultraviolet and deep ultraviolet lasers, which is the most widely and directly and effectively method for generating ultraviolet and deep ultraviolet lasers at present; secondly, the sensitivity of human eyes to green light is high, and the green light laser has the characteristics of short wavelength, high photon energy, high resolution and the like, so that the green light pulse laser can be utilized for ophthalmic surgery treatment; in addition, the attenuation of the seawater to blue-green light is much smaller than that of light in other wave bands, and a low-loss light transmission window exists, so that the laser in the green wave band can be used for underwater long-distance communication and laser underwater detection. The laser high-order mode has important functions in the fields of particle manipulation, laser processing, communication transmission and the like due to the unique spatial structure and phase distribution. Common laser high order mode wired polarization mode (LP), orbital angular momentum mode (OAM), lager-gaussian mode, causal-gaussian mode, hermite-gaussian mode, etc. The generation of the higher order modes of the green light band will expand the range of application of the higher order modes.
The high-order mode is generated in various modes, one is a method adopting spatial light modulation, and the method mainly utilizes a liquid crystal spatial light modulator, but is limited by low damage threshold of liquid crystal, so that the method is difficult to realize high-power output; the other method is to directly generate the high-order mode by a resonant cavity mode, so that the obtained high-order mode is purer and high-power output is easier to realize. The method is divided into two modes of intracavity frequency multiplication and extracavity frequency multiplication, the green laser generated by intracavity frequency multiplication mainly outputs in a fundamental mode, and the conversion efficiency of extracavity frequency multiplication is lower. The solid laser needs a large amount of optical elements using free space, has a complex structure and increases debugging difficulty.
Disclosure of Invention
First, the technical problem to be solved
The invention mainly aims at the problems and provides a high-order mode nanosecond green laser which aims at solving the problems of how to realize laser amplification and maintaining the purity of the high-order mode in the amplification process.
(II) technical scheme
In order to achieve the above object, the present invention provides a high-order mode nanosecond green laser, comprising a semiconductor laser generating nanosecond seed laser, the semiconductor laser being connected with a fiber bandpass filter isolator via fiber fusion: the optical fiber band-pass filter isolator is sequentially connected with the power amplifier and the frequency multiplication light path through optical fiber fusion, wherein:
the power amplifier comprises a primary single-mode amplifier, a secondary multimode amplifier and a tertiary multimode amplifier, wherein the primary single-mode amplifier is a first single-mode polarization-preserving ytterbium-doped optical fiber amplifier of forward pumping or backward pumping, and the secondary multimode amplifier is a second multimode polarization-preserving ytterbium-doped optical fiber amplifier of unidirectional pumping or bidirectional pumping; the three-stage multimode amplifier is a third multimode polarization-preserving ytterbium-doped fiber amplifier of unidirectional pumping or bidirectional pumping.
Further, the first-stage single-mode amplifier includes: the optical fiber band-pass filter isolator is connected with the wavelength division multiplexer through optical fiber welding, the wavelength division multiplexer is connected with the first single-mode polarization-preserving ytterbium-doped optical fiber amplifier through optical fiber welding, and the first single-mode polarization-preserving ytterbium-doped optical fiber amplifier is connected with the first optical fiber isolator through optical fiber welding.
Further, the second-stage multimode amplifier comprises a first signal pump beam combiner, a second multimode polarization-preserving ytterbium-doped optical fiber amplifier and a second optical fiber isolator; the first optical fiber isolator and the first semiconductor multimode pump laser are connected to a first signal pump beam combiner through optical fiber fusion, the first signal pump beam combiner is connected with the second multimode polarization-preserving ytterbium-doped optical fiber amplifier through optical fiber fusion, and the second multimode polarization-preserving ytterbium-doped optical fiber amplifier is connected with the second optical fiber isolator through optical fiber fusion.
Further, the device also comprises a polarization maintaining coupler, wherein four channels of the polarization maintaining coupler are respectively connected with the second optical fiber isolator, the mode field adapter, the first photoelectric detector and the second photoelectric detector.
Further, the three-stage multimode amplifier comprises a mode field adapter, a second signal pump beam combiner, a third multimode polarization-maintaining ytterbium-doped fiber amplifier, a cladding power stripper, a mode converter and a fiber collimator; the second signal pump beam combiner, the third multimode polarization-preserving ytterbium-doped optical fiber amplifier, the cladding power stripper, the mode converter and the optical fiber collimator are connected in sequence through an optical fiber welding mode.
Further, the frequency multiplication light path is composed of a focusing lens, a frequency doubling LBO crystal and a heating furnace thereof, a first dichroic mirror, a second dichroic mirror and a collimating lens, which are sequentially arranged.
Further, the principal plane of the frequency doubling LBO crystal is an XY plane, and the crystal angle is θ=90°, Φ=0°; the front and back surfaces of the double frequency LBO crystal are coated with infrared and 532nm antireflection films.
Further, the tail fibers of the signal end and the public end of the first signal pump beam combiner are passive double-clad fibers, the fiber core diameter of the passive double-clad fibers is 10 mu m, and the inner cladding diameter of the passive double-clad fibers is 125 mu m; the tail fiber of the pumping end is multimode fiber, the fiber core diameter is 105 mu m, the cladding diameter is 125 mu m, and the fiber core numerical aperture is 0.22; the second multimode polarization-maintaining ytterbium-doped optical fiber amplifier is an active double-cladding YDF, the fiber core diameter is 10 mu m, the inner cladding diameter is 125 mu m, the fiber core numerical aperture is 0.08, and the fiber length is 4m; the optical fiber of the second fiber isolator is a PM980 fiber.
Further, the mode field adapter is formed by drawing PLMA-GDF-10/125-M and PLMA-GDF-25/250-M optical fibers, the signal end and the common end tail fiber of the second signal pump beam combiner are passive double-clad optical fibers, the fiber core diameter is 25 mu M, and the inner cladding diameter is 250 mu M; the tail fiber of the pumping end is multimode fiber, the fiber core diameter is 105 mu m, the cladding diameter is 125 mu m, and the fiber core numerical aperture is 0.22; the third multimode polarization-maintaining ytterbium-doped fiber amplifier is an active double-cladding YDF, the fiber core diameter is 25 mu m, the inner cladding diameter is 250 mu m, the fiber core numerical aperture is 0.075, and the fiber length is 3m; the tail fibers of the cladding power stripper and the fiber collimator are both passive double-cladding fibers, the fiber core diameter of the fiber is 25 mu m, and the inner cladding diameter is 250 mu m; the mode converter uses an optical fiber consistent with a cladding power stripper pigtail.
Further, the high-order mode of the high-order mode nanosecond green laser is to realize conversion from the basic mode to the high-order mode by the mode converter, and any high-order mode output such as a high-order OAM mode and the like can be realized by selecting a proper mode converter.
In order to achieve the above object, the present invention provides a high-order mode nanosecond green laser, comprising a semiconductor laser generating nanosecond seed laser, the semiconductor laser being connected with a fiber bandpass filter isolator via fiber fusion: the optical fiber band-pass filter isolator is sequentially connected with a power amplifier and a frequency multiplication light path through optical fiber fusion, wherein the power amplifier comprises:
the first-stage single-mode amplifier comprises a wavelength division multiplexer, a semiconductor single-mode pump laser, a first single-mode polarization-preserving ytterbium-doped optical fiber amplifier and a first optical fiber isolator, wherein the optical fiber bandpass filter isolator and the semiconductor single-mode pump laser are connected with the wavelength division multiplexer through optical fiber fusion, the wavelength division multiplexer is connected with the first single-mode polarization-preserving ytterbium-doped optical fiber amplifier through optical fiber fusion, and the first single-mode polarization-preserving ytterbium-doped optical fiber amplifier is connected with the first optical fiber isolator through optical fiber fusion;
the second-stage multimode amplifier comprises a first signal pump beam combiner, a second multimode polarization-maintaining ytterbium-doped optical fiber amplifier and a second optical fiber isolator; the first optical fiber isolator is connected to the mode converter through optical fiber fusion, the mode converter and the first semiconductor multimode pump laser are connected to the first signal pump beam combiner through optical fiber fusion, the first signal pump beam combiner is connected with the second multimode polarization-preserving ytterbium-doped optical fiber amplifier through optical fiber fusion, and the second multimode polarization-preserving ytterbium-doped optical fiber amplifier is connected with the second optical fiber isolator through optical fiber fusion;
the four channels of the polarization maintaining coupler are respectively connected with the second optical fiber isolator, the mode field adapter, the first photoelectric detector and the second photoelectric detector;
the three-stage multimode amplifier comprises a mode field adapter, a second signal pump beam combiner, a third multimode polarization-preserving ytterbium-doped optical fiber amplifier, a cladding power stripper and an optical fiber collimator; the second signal pump beam combiner, the third multimode polarization-preserving ytterbium-doped optical fiber amplifier, the cladding power stripper and the optical fiber collimator are connected in sequence in an optical fiber welding mode;
the frequency multiplication light path consists of a focusing lens, a frequency doubling LBO crystal, a heating furnace thereof, a first dichroic mirror, a second dichroic mirror and a collimating lens, which are arranged in sequence.
(III) beneficial effects
Compared with the prior art, the high-order mode nanosecond green laser provided by the invention realizes high-power and high-quality green light output by improving the laser path structure and performing the processes of step-by-step power amplification and mode conversion on seed laser. The solid laser has compact structure and lower power consumption due to the requirement of a large number of space components and a large number of heat sink structures and the adoption of the all-fiber structure to realize the output of fundamental frequency light of a high-order mode.
Drawings
Fig. 1 is a schematic diagram of an optical path of a high-order mode nanosecond green laser disclosed in the present application.
Fig. 2 is a schematic diagram of a modification of the optical path of a high-order mode nanosecond green laser disclosed in the present application.
Reference numerals shown in the drawings: 1. a semiconductor laser; 2. an optical fiber bandpass filter isolator; 3. a wavelength division multiplexer; 4. a semiconductor single-mode pump laser; 5. the first single-mode polarization-maintaining ytterbium-doped optical fiber amplifier; 6. a first fiber optic isolator; 7. a first semiconductor multimode pump laser; 8. a first signal pump combiner; 9. the second multimode polarization-maintaining ytterbium-doped optical fiber amplifier; 10. a second fiber isolator; 11. a polarization maintaining coupler; 12. a first photodetector; 13. a second photodetector; 14. a mode field adapter; 15. a second semiconductor multimode pump laser; 16. a second signal pump combiner; 17. the third multimode polarization-maintaining ytterbium-doped optical fiber amplifier; 18. a cladding power stripper; 19. a mode converter; 20. an optical fiber collimator; 21. a focusing lens; 22. double frequency LBO crystal and heating furnace thereof; 23. a first dichroic mirror; 24. a second dichroic mirror; 25. a collimating lens.
Detailed Description
The following describes in further detail the embodiments of the present invention with reference to the drawings and examples. The following examples are illustrative of the invention and are not intended to limit the scope of the invention.
In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, are merely for convenience in describing the present invention and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a specific orientation, be configured and operated in a specific orientation, and thus should not be construed as limiting the present invention. Furthermore, the terms "first," "second," and the like, are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.
In the description of the present invention, it should be noted that, unless explicitly specified and limited otherwise, the terms "mounted," "connected," and "connected" are to be construed broadly, and may be either fixedly connected, detachably connected, or integrally connected, for example; can be mechanically or electrically connected; can be directly connected or indirectly connected through an intermediate medium, and can be communication between two elements. The specific meaning of the above terms in the present invention will be understood in specific cases by those of ordinary skill in the art.
The technology relates to a design of a high-order mode nanosecond green laser, which can be mainly used in the fields of underwater communication and the like. It has more advantages than the traditional solid green laser, such as more compact structure, higher conversion efficiency, etc.
First, the laser uses a 1064nm semiconductor seed source 1, and outputs laser with a central wavelength of 1064nm by an electric control direct modulation mode. The power of the laser is then amplified to the desired level by a process called pumping.
To achieve the output of higher order modes (i.e. create more complex laser shapes), the present embodiment uses the device of the mode converter 19. Then, the power of the laser is again increased while maintaining the purity of the higher order modes.
Finally, in the frequency doubling optical path section, the present embodiment uses a special crystal (LBO crystal) and a heating furnace to double the frequency of the laser beam, thereby obtaining the desired green light. By adjusting the temperature of the focusing lens 21 and the collimator lens 25 and the heating furnace, it is ensured that the finally output green light has the proper power and spot size.
The ability to communicate in complex environments (e.g., underwater) is further enhanced by providing a more efficient, compact green laser design, but also by being able to output higher order modes of laser light.
The fundamental frequency light path of the high-order mode nanosecond green laser adopts an all-fiber technical system, and has the advantages of simple and compact structure, high conversion efficiency and the like compared with the traditional solid green laser; in addition, compared with the traditional mode of nanosecond green laser output, the mode of the invention is the fundamental mode (TEM 00 mode), the invention realizes the nanosecond green laser output of the high-order mode, and can effectively improve the transmission capacity of the underwater green communication system.
Example 1:
as shown in fig. 1, the high-order mode nanosecond green laser provided by the application comprises a semiconductor laser 1 for generating nanosecond seed laser, wherein the semiconductor laser 1 is connected with an optical fiber band-pass filter isolator 2 through optical fiber fusion: the optical fiber band-pass filter isolator 2 is sequentially connected with a power amplifier and a frequency multiplication light path through optical fiber fusion, wherein:
the power amplifier comprises a primary single-mode amplifier, a secondary multimode amplifier and a tertiary multimode amplifier, wherein the primary single-mode amplifier is a first single-mode polarization-preserving ytterbium-doped optical fiber amplifier 5 of forward pumping or backward pumping, and the secondary multimode amplifier is a second multimode polarization-preserving ytterbium-doped optical fiber amplifier 9 of unidirectional pumping or bidirectional pumping; the three-stage multimode amplifier is a third multimode polarization-preserving ytterbium-doped fiber amplifier 17 of unidirectional pumping or bidirectional pumping.
The primary single-mode amplifier includes: the optical fiber band-pass filter isolator comprises a wavelength division multiplexer 3, a semiconductor single-mode pump laser 4, a first single-mode polarization-preserving ytterbium-doped optical fiber amplifier 5 and a first optical fiber isolator 6, wherein the optical fiber band-pass filter isolator 2 and the semiconductor single-mode pump laser 4 are connected with the wavelength division multiplexer 3 through optical fiber fusion, the wavelength division multiplexer 3 is connected with the first single-mode polarization-preserving ytterbium-doped optical fiber amplifier 5 through optical fiber fusion, and the first single-mode polarization-preserving ytterbium-doped optical fiber amplifier 5 is connected with the first optical fiber isolator 6 through optical fiber fusion.
The second-stage multimode amplifier comprises a first signal pump beam combiner 8, a second multimode polarization-maintaining ytterbium-doped optical fiber amplifier 9 and a second optical fiber isolator 10; the first fiber isolator 6 and the first semiconductor multimode pump laser 7 are connected to the first signal pump combiner 8 through fiber fusion, the first signal pump combiner 8 is connected to the second multimode polarization-preserving ytterbium-doped fiber amplifier 9 through fiber fusion, and the second multimode polarization-preserving ytterbium-doped fiber amplifier 9 is connected to the second fiber isolator 10 through fiber fusion.
The device further comprises a polarization maintaining coupler 11, wherein four channels of the polarization maintaining coupler 11 are respectively connected with the second optical fiber isolator 10, the mode field adapter 14, the first photoelectric detector 12 and the second photoelectric detector 13 for power monitoring and protection functions.
The three-stage multimode amplifier comprises a mode field adapter 14, a second signal pump beam combiner 16, a third multimode polarization-preserving ytterbium-doped optical fiber amplifier 17, a cladding power stripper 18, a mode converter 19 and an optical fiber collimator 20; the mode field adapter 14 and the second semiconductor multimode pump laser 15 are connected with the second signal pump beam combiner 16 through optical fiber fusion, and the second signal pump beam combiner 16, the third multimode polarization-preserving ytterbium-doped optical fiber amplifier 17, the cladding power stripper 18, the mode converter 19 and the optical fiber collimator 20 are connected in sequence through optical fiber fusion. This level of amplifier further enhances the power and enables conversion of the fundamental mode to higher order modes by the mode converter.
The 1064nm semiconductor seed source outputs laser with the central wavelength of 1064nm and the pulse width of ns magnitude in an electric control direct modulation mode, and the output optical fiber is PM980 optical fiber. The seed laser is filtered and isolated by an optical fiber band-pass filter isolator 2.
The primary single-mode amplifier consists of a 980/1064 polarization-maintaining wavelength division multiplexer 3, a 976nm 600mW semiconductor single-mode pump laser 4, a first section of single-mode polarization-maintaining ytterbium-doped fiber amplifier 5 and a first fiber isolator 6. The components are connected by fusion splicing. The first-stage single-mode amplifier amplifies the seed laser signal.
The second-stage multimode amplifier consists of a first signal pump beam combiner 8, a second multimode polarization-maintaining ytterbium-doped optical fiber amplifier 9 and a second optical fiber isolator 10. The first signal pump combiner 8 is a device of the type (2+1) x 1 for combining and separating different optical signals. This level of amplifier further amplifies the power. In the embodiment, the tail fibers of the signal end and the public end of the first signal pump beam combiner 8 are passive double-clad fibers, the fiber core diameter of the passive double-clad fibers is 10 mu m, and the inner cladding diameter of the passive double-clad fibers is 125 mu m; the tail fiber of the pumping end is multimode fiber, the fiber core diameter is 105 mu m, the cladding diameter is 125 mu m, and the fiber core numerical aperture is 0.22; the second multimode polarization-maintaining ytterbium-doped fiber amplifier 9 is an active double-cladding YDF, the fiber core diameter is 10 mu m, the inner cladding diameter is 125 mu m, the fiber core numerical aperture is 0.08, and the fiber length is 4m; the optical fiber of the second fiber isolator 10 is a PM980 fiber.
The frequency multiplication light path is composed of a focusing lens 21, a frequency doubling LBO crystal, a heating furnace 22, a first dichroic mirror 23, a second dichroic mirror 24 and a collimating lens 25. In this part, the green light is subjected to second harmonic generation by the frequency doubling crystal, resulting in output green light. The temperature of the heating furnace, the position and the angle of the frequency doubling LBO crystal are optimized by green light power; the focal lengths of the focusing lens 21 and the collimator lens 25 are determined by the green power and the spot size.
In some embodiments, the principal plane of the frequency doubling LBO crystal is an XY plane, and the crystal angle is θ=90°, Φ=0°, for reducing walk-off effects, and further reducing ellipticity of the output green light; the front and back surfaces of the double frequency LBO crystal are coated with infrared and 532nm antireflection films.
In some embodiments, mode field adaptor 14 is drawn from PLMA-GDF-10/125-M and PLMA-GDF-25/250-M fibers, and the signal end, common end pigtail, of second signal pump combiner 16 is a passive double-clad fiber having a core diameter of 25 μm and an inner cladding diameter of 250 μm; the tail fiber of the pumping end is multimode fiber, the fiber core diameter is 105 mu m, the cladding diameter is 125 mu m, and the fiber core numerical aperture is 0.22; the third multimode polarization-maintaining ytterbium-doped fiber amplifier 17 is an active double-cladding YDF, the fiber core diameter is 25 mu m, the inner cladding diameter is 250 mu m, the fiber core numerical aperture is 0.075, and the fiber length is 3m; the tail fibers of the cladding power stripper 18 and the fiber collimator 20 are both passive double-cladding fibers, the fiber core diameter is 25 mu m, and the inner cladding diameter is 250 mu m; the mode converter 19 uses optical fibers that are pigtail identical to the cladding power stripper 18.
Through the above steps, the high-order mode nanosecond green laser of embodiment 1 can realize a process from seed laser to final output of green light. The combination and adjustment of the amplifiers and frequency doubling optical paths ensures the amplification of the laser signal and the output of higher order modes.
Example 2:
as shown in fig. 2, the present application further provides a high-order mode nanosecond green laser, which includes a semiconductor laser 1 generating nanosecond seed laser, wherein the semiconductor laser 1 is connected with a fiber bandpass filter isolator 2 via fiber fusion: the optical fiber band-pass filter isolator 2 is sequentially connected with a power amplifier and a frequency multiplication light path through optical fiber fusion, wherein the power amplifier comprises:
the first-stage single-mode amplifier comprises a wavelength division multiplexer 3, a semiconductor single-mode pump laser 4, a first single-mode polarization-preserving ytterbium-doped optical fiber amplifier 5 and a first optical fiber isolator 6, wherein the optical fiber bandpass filter isolator 2 and the semiconductor single-mode pump laser 4 are connected with the wavelength division multiplexer 3 through optical fiber fusion, the wavelength division multiplexer 3 is connected with the first single-mode polarization-preserving ytterbium-doped optical fiber amplifier 5 through optical fiber fusion, and the first single-mode polarization-preserving ytterbium-doped optical fiber amplifier 5 is connected with the first optical fiber isolator 6 through optical fiber fusion;
the second-stage multimode amplifier comprises a first signal pump beam combiner 8, a second multimode polarization-maintaining ytterbium-doped optical fiber amplifier 9 and a second optical fiber isolator 10; the first optical fiber isolator 6 is connected to the mode converter 19 through optical fiber fusion, the mode converter 19 and the first semiconductor multimode pump laser 7 are connected to the first signal pump beam combiner 8 through optical fiber fusion, the first signal pump beam combiner 8 is connected with the second multimode polarization-preserving ytterbium-doped optical fiber amplifier 9 through optical fiber fusion, and the second multimode polarization-preserving ytterbium-doped optical fiber amplifier 9 is connected with the second optical fiber isolator 10 through optical fiber fusion; the mode converter 19 realizes conversion from a fundamental mode to a higher-order mode, and the realization form includes a long-period fiber grating, a mode selection coupler, and the like.
The polarization maintaining coupler 11, four channels of the polarization maintaining coupler 11 are respectively connected with the second optical fiber isolator 10, the mode field adapter 14, the first photoelectric detector 12 and the second photoelectric detector 13;
the three-stage multimode amplifier comprises a mode field adapter 14, a second signal pump beam combiner 16, a third multimode polarization-maintaining ytterbium-doped fiber amplifier 17, a cladding power stripper 18 and a fiber collimator 20; the mode field adapter 14 and the second semiconductor multimode pump laser 15 are connected with the second signal pump beam combiner 16 through optical fiber fusion, and the second signal pump beam combiner 16, the third multimode polarization-preserving ytterbium-doped optical fiber amplifier 17, the cladding power stripper 18 and the optical fiber collimator 20 are connected in sequence through an optical fiber fusion mode;
the frequency doubling optical path is composed of a focusing lens 21, a frequency doubling LBO crystal, a heating furnace 22, a first dichroic mirror 23, a second dichroic mirror 24, and a collimator lens 25, which are sequentially arranged.
In example 1, a 1064nm semiconductor seed source outputs laser light with a center wavelength of 1064nm by means of electronically controlled direct modulation. Then, the amplification process of several steps including the use of single-mode amplifier, amplification stage, main amplification stage, etc. (i.e., one-stage single-mode amplifier, two-stage multimode amplifier, and three-stage multimode amplifier) results in a significant enhancement of the initial laser power. An important element is the use of a mode converter 19 which is capable of converting the basic laser mode into a higher order mode. The converted high-order mode nanosecond laser continues to perform power amplification in the main amplification stage. Finally, in the frequency doubling light path part, the frequency of the laser is doubled by a focusing lens 21, a frequency doubling LBO crystal and temperature control, green light power and spot size are optimized, and finally the required green light laser is output.
Example 2 is similar to example 1, but differs in the laser amplification process. After single mode amplification, a mode converter is directly used to effect conversion of the fundamental mode to higher order modes. The two-stage amplification is then used to power amplify the converted higher order modes while maintaining the purity of the higher order modes as much as possible. And finally, the frequency of the laser is doubled in a frequency multiplication light path part through a focusing lens, a frequency doubling LBO crystal and temperature control, green light power and spot size are optimized, and finally the required green light laser is output.
It will be appreciated that the main difference between the two embodiments is the order of laser amplification and mode conversion, and the method of maintaining higher order mode purity during amplification.
The foregoing is merely a preferred embodiment of the present invention, and it should be noted that it will be apparent to those skilled in the art that modifications and variations can be made without departing from the technical principles of the present invention, and these modifications and variations should also be regarded as the scope of the invention.
Claims (10)
1. A high order mode nanosecond green laser comprising a semiconductor laser (1) producing nanosecond seed laser light, the semiconductor laser (1) being connected to a fiber bandpass filter isolator (2) via fiber fusion: the optical fiber band-pass filter isolator (2) is sequentially connected with the power amplifier and the frequency multiplication light path through optical fiber fusion, wherein:
the power amplifier comprises a primary single-mode amplifier, a secondary multimode amplifier and a tertiary multimode amplifier, wherein the primary single-mode amplifier is a first single-mode polarization-preserving ytterbium-doped optical fiber amplifier (5) of forward pumping or backward pumping, and the secondary multimode amplifier is a second multimode polarization-preserving ytterbium-doped optical fiber amplifier (9) of unidirectional pumping or bidirectional pumping; the three-stage multimode amplifier is a third multimode polarization-preserving ytterbium-doped fiber amplifier (17) with unidirectional pumping or bidirectional pumping.
2. A higher order mode nanosecond green laser as recited in claim 1, wherein said primary single mode amplifier comprises: the optical fiber band-pass filter isolator comprises a wavelength division multiplexer (3), a semiconductor single-mode pump laser (4), a first single-mode polarization-preserving ytterbium-doped optical fiber amplifier (5) and a first optical fiber isolator (6), wherein the optical fiber band-pass filter isolator (2) and the semiconductor single-mode pump laser (4) are connected with the wavelength division multiplexer (3) through optical fiber fusion, the wavelength division multiplexer (3) is connected with the first single-mode polarization-preserving ytterbium-doped optical fiber amplifier (5) through optical fiber fusion, and the first single-mode polarization-preserving ytterbium-doped optical fiber amplifier (5) is connected with the first optical fiber isolator (6) through optical fiber fusion.
3. A high order mode nanosecond green laser as claimed in claim 2, wherein the second multimode amplifier comprises a first signal pump combiner (8), a second multimode polarization-maintaining ytterbium-doped fiber amplifier (9), and a second fiber isolator (10); the first optical fiber isolator (6) and the first semiconductor multimode pump laser (7) are connected to the first signal pump beam combiner (8) through optical fiber fusion, the first signal pump beam combiner (8) is connected with the second multimode polarization-preserving ytterbium-doped optical fiber amplifier (9) through optical fiber fusion, and the second multimode polarization-preserving ytterbium-doped optical fiber amplifier (9) is connected with the second optical fiber isolator (10) through optical fiber fusion.
4. A higher order mode nanosecond green laser as claimed in claim 3, further comprising a polarization maintaining coupler (11), wherein the four channels of the polarization maintaining coupler (11) are connected to the second fiber isolator (10), the mode field adapter (14), the first photodetector (12) and the second photodetector (13), respectively.
5. A high order mode nanosecond green laser as claimed in claim 4, wherein the three-stage multimode amplifier comprises a mode field adaptor (14), a second signal pump combiner (16), a third multimode polarization-maintaining ytterbium-doped fiber amplifier (17), a cladding power stripper (18), a mode converter (19), and a fiber collimator (20); the mode field adapter (14) and the second semiconductor multimode pump laser (15) are connected with the second signal pump beam combiner (16) through optical fiber fusion, and the second signal pump beam combiner (16), the third multimode polarization-preserving ytterbium-doped optical fiber amplifier (17), the cladding power stripper (18), the mode converter (19) and the optical fiber collimator (20) are connected in sequence through an optical fiber fusion mode.
6. A higher order mode nanosecond green laser as claimed in claim 5, characterized in that the frequency doubled light is composed of a focusing lens (21), a frequency doubled LBO crystal and its heating furnace (22), a first dichroic mirror (23) and a second dichroic mirror (24), a collimating lens (25) arranged in sequence.
7. A higher order mode nanosecond green laser as claimed in claim 6, wherein the principal plane of the frequency doubling LBO crystal is XY plane, the crystal angle is θ=90°, Φ=0°; the front and back surfaces of the double frequency LBO crystal are coated with infrared and 532nm antireflection films.
8. A high-order mode nanosecond green laser as claimed in claim 3, wherein the signal end and the common end tail fiber of the first signal pump beam combiner (8) are passive double-clad optical fibers, the fiber core diameter is 10 μm, and the inner cladding diameter is 125 μm; the tail fiber of the pumping end is multimode fiber, the fiber core diameter is 105 mu m, the cladding diameter is 125 mu m, and the fiber core numerical aperture is 0.22; the second multimode polarization-maintaining ytterbium-doped optical fiber amplifier (9) is an active double-cladding YDF, the fiber core diameter is 10 mu m, the inner cladding diameter is 125 mu m, the fiber core numerical aperture is 0.08, and the fiber length is 4m; the optical fiber of the second fiber isolator (10) is a PM980 fiber.
9. A higher-order mode nanosecond green laser as claimed in claim 5, wherein the mode field adaptor (14) is drawn from PLMA-GDF-10/125-M and PLMA-GDF-25/250-M fibers, the signal end and common end pigtail of the second signal pump combiner (16) are passive double-clad fibers with a core diameter of 25 μm and an inner cladding diameter of 250 μm; the tail fiber of the pumping end is multimode fiber, the fiber core diameter is 105 mu m, the cladding diameter is 125 mu m, and the fiber core numerical aperture is 0.22; the third multimode polarization-maintaining ytterbium-doped optical fiber amplifier (17) is an active double-cladding YDF, the fiber core diameter is 25 mu m, the inner cladding diameter is 250 mu m, the fiber core numerical aperture is 0.075, and the fiber length is 3m; the tail fibers of the cladding power stripper (18) and the fiber collimator (20) are passive double-cladding fibers, the fiber core diameter is 25 mu m, and the inner cladding diameter is 250 mu m; the mode converter (19) uses an optical fiber consistent with the pigtail of the cladding power stripper (18).
10. A high order mode nanosecond green laser comprising a semiconductor laser (1) producing nanosecond seed laser light, the semiconductor laser (1) being connected to a fiber bandpass filter isolator (2) via fiber fusion: the optical fiber band-pass filter isolator (2) is sequentially connected with a power amplifier and a frequency multiplication light path through optical fiber fusion, wherein the power amplifier comprises:
the first-stage single-mode amplifier comprises a wavelength division multiplexer (3), a semiconductor single-mode pump laser (4), a first single-mode polarization-preserving ytterbium-doped optical fiber amplifier (5) and a first optical fiber isolator (6), wherein the optical fiber bandpass filter isolator (2) and the semiconductor single-mode pump laser (4) are connected with the wavelength division multiplexer (3) through optical fiber fusion, the wavelength division multiplexer (3) is connected with the first single-mode polarization-preserving ytterbium-doped optical fiber amplifier (5) through optical fiber fusion, and the first single-mode polarization-preserving ytterbium-doped optical fiber amplifier (5) is connected with the first optical fiber isolator (6) through optical fiber fusion;
the second-stage multimode amplifier comprises a first signal pump beam combiner (8), a second multimode polarization-preserving ytterbium-doped optical fiber amplifier (9) and a second optical fiber isolator (10); the first optical fiber isolator (6) is connected to a mode converter (19) through optical fiber fusion, the mode converter (19) and the first semiconductor multimode pump laser (7) are connected to a first signal pump beam combiner (8) through optical fiber fusion, the first signal pump beam combiner (8) is connected with the second multimode polarization-preserving ytterbium-doped optical fiber amplifier (9) through optical fiber fusion, and the second multimode polarization-preserving ytterbium-doped optical fiber amplifier (9) is connected with the second optical fiber isolator (10) through optical fiber fusion;
the four channels of the polarization maintaining coupler (11) are respectively connected with the second optical fiber isolator (10), the mode field adapter (14), the first photoelectric detector (12) and the second photoelectric detector (13);
the three-stage multimode amplifier comprises a mode field adapter (14), a second signal pump beam combiner (16), a third multimode polarization-maintaining ytterbium-doped optical fiber amplifier (17), a cladding power stripper (18) and an optical fiber collimator (20); the mode field adapter (14) and the second semiconductor multimode pump laser (15) are connected with a second signal pump beam combiner (16) through optical fiber fusion, and the second signal pump beam combiner (16), a third multimode polarization-preserving ytterbium-doped optical fiber amplifier (17), a cladding power stripper (18) and an optical fiber collimator (20) are connected in sequence through an optical fiber fusion mode;
the frequency multiplication light route is composed of a focusing lens (21), a frequency doubling LBO crystal, a heating furnace (22) of the frequency doubling LBO crystal, a first dichroic mirror (23), a second dichroic mirror (24) and a collimating lens (25), which are arranged in sequence.
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