CN108767637B - THz high repetition frequency high power femtosecond optical fiber laser based on scattered wave - Google Patents
THz high repetition frequency high power femtosecond optical fiber laser based on scattered wave Download PDFInfo
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- 229910052691 Erbium Inorganic materials 0.000 claims description 2
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- 101100456571 Mus musculus Med12 gene Proteins 0.000 description 5
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- 238000005086 pumping Methods 0.000 description 4
- NAWDYIZEMPQZHO-UHFFFAOYSA-N ytterbium Chemical compound [Yb] NAWDYIZEMPQZHO-UHFFFAOYSA-N 0.000 description 4
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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
- H01S3/06708—Constructional details of the fibre, e.g. compositions, cross-section, shape or tapering
- H01S3/06716—Fibre compositions or doping with active elements
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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
- 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
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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
- H01S3/09—Processes or apparatus for excitation, e.g. pumping
- H01S3/091—Processes or apparatus for excitation, e.g. pumping using optical pumping
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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
- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/10—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating
- H01S3/10084—Frequency control by seeding
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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
- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/10—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating
- H01S3/106—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating by controlling devices placed within the cavity
- H01S3/108—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating by controlling devices placed within the cavity using non-linear optical devices, e.g. exhibiting Brillouin or Raman scattering
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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
- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/10—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating
- H01S3/106—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating by controlling devices placed within the cavity
- H01S3/108—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating by controlling devices placed within the cavity using non-linear optical devices, e.g. exhibiting Brillouin or Raman scattering
- H01S3/109—Frequency multiplication, e.g. harmonic generation
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Abstract
The invention discloses a THz high repetition frequency high power femtosecond fiber laser based on scattered wave, which comprises an erbium-doped fiber laser seed source, a frequency lifting part, an amplifying part and a pulse width compressing part; the output end of the seed source of the erbium-doped fiber laser is connected with the frequency lifting part through a high nonlinear fiber, the output end of the frequency lifting part is connected to the amplifying part, the amplifying part comprises a pre-amplifying part and a two-stage main amplifying part, and the output end of the amplifying part is connected with the pulse width compressing part; the laser signal generated by the seed source of the erbium-doped fiber laser is subjected to nonlinear frequency conversion by the high nonlinear fiber and is subjected to frequency lifting to THz high repetition frequency by the frequency lifting part, the laser signal of the THz high repetition frequency is subjected to power amplification by the pre-amplification part of the amplification part and the two-stage main amplification part, and then is subjected to pulse width compression part to output a high-power femtosecond pulse signal of the THz high repetition frequency. The invention has simple installation structure, easy realization, low cost and convenient popularization.
Description
Technical Field
The invention relates to the technical field of laser, in particular to a THz high repetition frequency high power femtosecond fiber laser based on scattered wave.
Background
The high-power femtosecond fiber laser has the advantages of high beam quality, good thermal stability, high peak power, compact structure, low cost, good environmental stability, no need of maintenance and the like, is widely applied in the fields of precision machining, waveguide etching, supercontinuum generation, laser sensing and the like, and is gradually focused by researchers. At present, the erbium-doped optical fiber with 1550nm wave band can better control the dispersion value in the resonant cavity of the optical fiber laser by selecting optical fibers with different lengths and different dispersions due to the optical fibers with positive dispersion and negative dispersion, so as to realize the output of femtosecond laser signals. For 1064nm wave band, the dispersion value of the optical fiber in the wave band is positive, the chirped Bragg fiber grating and the photonic crystal fiber for carrying out dispersion compensation on the optical fiber are required to be customized, and the cost is high, so that the ytterbium-doped fiber laser of the 1064nm wave band has higher difficulty in obtaining femtosecond laser pulse output. The high power is generally obtained by adopting a MOPA structure, and a femtosecond fiber laser with lower power pulse laser output obtained by mode locking can realize laser signal output with higher pulse energy and average power through MOPA amplification.
The main method for obtaining high repetition frequency in the passive mode-locked fiber laser is to lock the mode through higher harmonic waves and shorten the length of the resonant cavity of the fiber laser. The higher harmonic mode locking is required to greatly improve the pumping power of the pumping laser on the basis of fundamental frequency mode locking, and the uniformity and stability of the output laser signals are poor because the pumping power is not in a fundamental frequency working state; and the rise of the pumping power increases the pulse energy in the resonant cavity of the whole laser, so that the service life of the passive mode locking element is influenced and the phenomenon of multiple pulses is generated. The repetition frequency of mode locking pulse can be effectively improved by shortening the length of the resonant cavity, but the shorter the cavity is, the fewer modes participating in mode locking are, and the mode locking difficulty is correspondingly increased. In addition, it is difficult to achieve particularly high repetition rates for both harmonic mode locking and short cavity mode locking, which is limited by its own mechanism, and it is difficult to achieve THz repetition rates using both methods. In the application of the optical frequency comb, the mode-locked fiber laser is required to have higher repetition frequency, and the high repetition frequency of the fiber laser can increase the comb teeth so as to meet the requirement of the frequency measurement application; in astronomical observation, the problems of high-precision view-direction speed calibration, accurate distance measurement, precision laser radar and other scientific research and national defense fields also need the fiber laser to have high repetition frequency.
Disclosure of Invention
In view of the above, it is necessary to provide a THz high repetition rate high power femtosecond fiber laser based on a scattered wave with stable beam quality and high output power.
A THz high repetition frequency high power femtosecond fiber laser based on scattered wave comprises an erbium-doped fiber laser seed source, a frequency lifting part, an amplifying part and a pulse width compressing part; the output end of the seed source of the erbium-doped fiber laser is connected with the frequency lifting part through a high nonlinear fiber, the output end of the frequency lifting part is connected to the amplifying part, the amplifying part comprises a pre-amplifying part and a two-stage main amplifying part, and the output end of the amplifying part is connected with the pulse width compressing part; the laser signal generated by the seed source of the erbium-doped fiber laser is subjected to nonlinear frequency conversion by the high nonlinear fiber and is subjected to frequency lifting to THz high repetition frequency by the frequency lifting part, the laser signal of the THz high repetition frequency is subjected to power amplification by the pre-amplification part of the amplification part and the two-stage main amplification part, and then is subjected to pulse width compression part to output a high-power femtosecond pulse signal of the THz high repetition frequency.
Further, the erbium-doped fiber laser seed source comprises a laser seed source and an erbium-doped fiber amplifying part, and the laser seed source comprises an optical reflector, a first erbium-doped gain fiber, a first wavelength division multiplexer and a first optical isolator which are connected in sequence; the two input ends of the first wavelength division multiplexer are respectively connected with the first erbium-doped gain optical fiber, the first single-mode pump laser and the output end of the driving circuit of the first single-mode pump laser, and the two output ends of the first wavelength division multiplexer are respectively connected with the input ends of the first optical isolator and the saturated absorber SESAM module.
Further, the first wavelength division multiplexer comprises a first optical fiber collimator, an optical filter, a polaroid, a Wollaston prism and a second optical fiber collimator which are sequentially connected; the input end of the first fiber collimator is connected to the optical reflector through the first erbium-doped gain fiber.
Further, the erbium-doped fiber amplifying part comprises a second wavelength division multiplexer, a second single-mode pump laser and a driving circuit thereof, and a second erbium-doped gain fiber, wherein the input end of the second wavelength division multiplexer is connected to the output end of the first optical isolator and the output end of the second single-mode pump laser and the driving circuit thereof, the output end of the second wavelength division multiplexer is connected to the second erbium-doped gain fiber, and the erbium-doped fiber amplifying part is used for improving the output power of the seed source of the erbium-doped fiber laser.
Further, an input end of the high nonlinearity fiber is connected to the second erbium-doped gain fiber, an output end of the high nonlinearity fiber is connected to the frequency boosting section, and the high nonlinearity fiber is used for performing nonlinear frequency conversion on an input laser signal.
Further, the frequency boosting part comprises cascaded 50/50 optical fiber couplers, the cascaded 50/50 optical fiber couplers comprise a first 1×2 50/50 optical fiber coupler, a plurality of 2×2 50/50 optical fiber couplers and a second 1×2 50/50 optical fiber coupler which are sequentially connected, the first 1×2 50/50 optical fiber coupler and the plurality of 2×2 50/50 optical fiber couplers are connected by adopting optical fibers, and the plurality of 2×2 50/50 optical fiber couplers and the second 1×2 50/50 optical fiber coupler are connected by adopting optical delay lines; the frequency lifting part adopts step-by-step frequency multiplication and is used for rapidly lifting the repetition frequency of the input laser signal.
Further, the pre-amplifying part comprises a first-stage pre-amplifying part and a second-stage pre-amplifying part, the first-stage pre-amplifying part comprises a third wavelength division multiplexer, a third single-mode pump laser and a driving circuit thereof, a first ytterbium-doped gain optical fiber and a second optical isolator, the input end of the third wavelength division multiplexer is connected to the output end of the frequency lifting part, the third single-mode pump laser and the driving circuit thereof, and the output end of the third wavelength division multiplexer is connected to the second optical isolator through a first ytterbium-doped gain optical fiber; the second-stage pre-amplification part comprises a fourth wavelength division multiplexer, a fourth single-mode pump laser and a driving circuit thereof, a second ytterbium-doped gain optical fiber and a third optical isolator, wherein the input end of the fourth wavelength division multiplexer is connected to the output end of the first pre-amplification part, the fourth single-mode pump laser and the driving circuit thereof, and the output end of the fourth wavelength division multiplexer is connected to the third optical isolator through the second ytterbium-doped gain optical fiber.
Further, the main amplifying part comprises a first-stage main amplifying part and a second-stage main amplifying part, the first-stage main amplifying part comprises a (2+1) x 1 optical combiner, a pair of multimode pump lasers and driving circuits thereof, a first double-cladding ytterbium-doped optical fiber and a first high-power optical isolator, the input end of the (2+1) x 1 optical combiner is connected to the output end of the second-stage pre-amplifying part and the pair of multimode pump lasers and driving circuits thereof, and the output end of the (2+1) x 1 optical combiner is connected to the first high-power optical isolator through the first double-cladding ytterbium-doped optical fiber; the second-stage main amplifying part comprises a (6+1) x 1 optical combiner, two groups of multimode pump lasers and driving circuits thereof, a second double-cladding ytterbium-doped optical fiber, a pump leakage device, a second high-power optical isolator and an end cap, wherein the input end of the (6+1) x 1 optical combiner is connected to the output end of the first-stage main amplifying part and the two groups of multimode pump lasers and driving circuits thereof, and the output end of the (6+1) x 1 optical combiner is sequentially connected to the pump leakage device, the second high-power optical isolator and the end cap through the second double-cladding ytterbium-doped optical fiber.
Further, the pump leakage device is used for filtering out residual pump light; the end cap is used for expanding the beam of the output signal light so as to avoid damage to the end face of the optical fiber; the first high-power optical isolator and the second high-power optical isolator are used for unidirectional transmission of laser signals.
Further, the pulse width compression part comprises a collimating mirror, a diffraction grating pair, a reflecting mirror and an output mirror, wherein the diffraction grating pair is used for compressing the output high-power femtosecond pulse laser signals so as to realize laser pulse signal output of narrower pulses; after passing through the collimating mirror, the laser signal is compressed by the diffraction grating pair and the reflecting mirror, and then is output through the output mirror.
In the THz high-repetition frequency high-power femtosecond fiber laser based on the dispersive wave, an erbium-doped fiber laser seed source is adopted to generate a femtosecond pulse signal with higher repetition frequency, the signal is amplified and then subjected to nonlinear frequency conversion of a section of high-nonlinearity fiber, a multistage frequency lifting part formed by a coupler is used to obtain the THz high-repetition frequency femtosecond pulse signal, and then the high-repetition frequency femtosecond pulse signal with low power is amplified to be output by a MOPA structure of pre-amplifying the ytterbium-doped fiber and main amplifying the two-stage ytterbium-doped double-clad fiber, and the laser signal with high repetition frequency is subjected to extracavity pulse width compression, so that the high-power laser signal output with high repetition frequency of the THz is obtained. The method has the advantages of simple installation structure, easy realization, low cost and convenient popularization.
Drawings
Fig. 1 is a schematic structural diagram of a THz high repetition rate high power femtosecond fiber laser based on a scattered wave according to an embodiment of the present invention.
Detailed Description
In this embodiment, a THz high repetition rate high power femtosecond fiber laser based on a scattered wave is taken as an example, and the present invention will be described in detail with reference to specific embodiments and drawings.
Referring to fig. 1, there is shown a THz high repetition frequency high power femtosecond fiber laser 100 based on a dispersion wave according to an embodiment of the present invention, including an erbium-doped fiber laser seed source 13, a frequency boost portion 27, an amplifying portion, and a pulse width compressing portion 56; the output end of the erbium-doped fiber laser seed source 13 is connected with the frequency lifting part 27 through a highly nonlinear optical fiber 19, the output end of the frequency lifting part 27 is connected with the amplifying part, the amplifying part comprises a pre-amplifying part 37 and a two-stage main amplifying part 50, and the output end of the amplifying part is connected with the pulse width compressing part 56; the laser signal generated by the erbium-doped fiber laser seed source 13 is converted by the nonlinear frequency of the high nonlinear fiber 19, and the frequency of the laser signal is raised to the THz high repetition frequency by the frequency raising part 27, the laser signal of the THz high repetition frequency is subjected to power amplification by the pre-amplifying part 37 and the two-stage main amplifying part 50 of the amplifying part, and then is subjected to output of the high power femtosecond pulse signal of the THz high repetition frequency by the pulse width compressing part 56.
Further, the erbium-doped fiber laser seed source 13 includes a laser seed source and an erbium-doped fiber amplifying section 18, and the laser seed source includes an optical mirror 1, a first erbium-doped gain fiber 2, a first wavelength division multiplexer 10, and a first optical isolator 7, which are sequentially connected; the two input ends of the first wavelength division multiplexer 10 are respectively connected with the output ends of the first erbium-doped gain optical fiber 2, the first single-mode pump laser 9 and the driving circuit thereof, and the two output ends of the first wavelength division multiplexer 10 are respectively connected with the input ends of the first optical isolator 7 and a saturable absorber SESAM module 11. The first wavelength division multiplexer 10 comprises a first optical fiber collimator 3, an optical filter 4, a polaroid 5, a Wollaston prism 12 and a second optical fiber collimator 6 which are sequentially connected; the input end of the first fiber collimator 3 is connected to the optical mirror 1 through the first erbium doped gain fiber 2. The erbium-doped fiber amplifying section 18 is configured to boost the output power of the erbium-doped fiber laser seed source 13, the erbium-doped fiber amplifying section 18 includes a second wavelength division multiplexer 16, a second single-mode pump laser 15 and a driving circuit thereof, and a second erbium-doped gain fiber 17, an input end of the second wavelength division multiplexer 16 is connected to an output end of the first optical isolator 7 and an output end of the second single-mode pump laser 15 and a driving circuit thereof, and an input end of the second wavelength division multiplexer 16 is connected to the second erbium-doped gain fiber 17.
Specifically, in the present embodiment, the first wavelength division multiplexer 10 and the second wavelength division multiplexer 16 use four-port 980/1550 wavelength division multiplexers. One end of the optical reflector 1 shares a section of high-concentration erbium-doped fiber with the reflective input end of the first wavelength division multiplexer 10, and the signal output end of the first wavelength division multiplexer 10 is connected with the collimator through a section of short tail fiber, so that the cavity length of the resonant cavity can be effectively reduced.
Specifically, the output percentage of the first wavelength division multiplexer 10 may adjust the output power, but the output percentage thereof needs to be matched with the lengths of the first erbium-doped gain fiber 2 and the pigtail in the resonant cavity to select a proper intra-cavity dispersion; and a filter plate is integrated and packaged in the light reflector 1, and the filter plate is used for controlling the central wavelength and the spectral bandwidth of an output signal so as to reduce the noise of the whole seed source system. The first optical fiber collimator 3 and the optical reflector 1 are packaged in an optical fiber mode, and the second optical fiber collimator 6 and the saturated absorber SESAM module 11 are packaged in a modularized mode so that stability of the system and compactness of the structure are guaranteed.
Preferably, the seed source 13 of the erbium-doped fiber laser adopts the saturated absorber SESAM module 11 to lock the mode, and proper parameters such as saturated flux, modulation depth, relaxation time and the like are selected to be matched with parameters in a laser resonant cavity so as to realize femtosecond pulse output; to prevent thermal damage to the saturable absorber SESAM module 11, the SESAM may be adhered to a base of heat sink material such as copper or aluminum and encapsulated by a glass tube.
In order to ensure that the system is not interfered by external environment in the operation process, each component in the seed source 13 of the erbium-doped fiber laser adopts a polarization maintaining device, and the seed source 13 of the femtosecond erbium-doped fiber laser has the self-starting and low threshold performance.
Further, an input end of the highly nonlinear optical fiber 19 is connected to the second erbium-doped gain optical fiber 17, an output end of the highly nonlinear optical fiber 19 is connected to the frequency boosting section 27, and the highly nonlinear optical fiber 19 is used for performing nonlinear frequency conversion on an input laser signal.
Specifically, the spectrum is widened from 1550nm band to 1064nm band by utilizing the nonlinear frequency conversion performance of the high nonlinear optical fiber 19, the length of the high nonlinear optical fiber 19 is shorter, and the high nonlinear optical fiber 19 is connected with the tail fiber of the optical fiber coupler of the frequency lifting part 27, and since the device and the tail fiber are both in 1064nm band, the laser signal in the required 1064nm band can be filtered and obtained.
Further, the frequency raising section 27 includes a cascade 50/50 fiber coupler, the cascade 50/50 fiber coupler includes a first 1×2 50/50 fiber coupler 20, a plurality of 2×2 50/50 fiber couplers 22, and a second 1×2 50/50 fiber coupler 26 connected in sequence, the first 1×2 50/50 fiber coupler 20 and the plurality of 2×2 50/50 fiber couplers 22 are connected by an optical fiber 21, and the plurality of 2×2 50/50 fiber couplers 22 and the second 1×2 50/50 fiber couplers 26 are connected by an optical delay line 25; the frequency boosting section 27 employs step-by-step frequency multiplication for rapidly boosting the repetition frequency of the input laser signal.
Specifically, the tail fiber of the optical fiber coupler adopts HI 1060 optical fiber, the arm length difference of two ends of the optical fiber coupler with lower repetition frequency is obtained by controlling the tail fiber length of two ends, and the tail fiber is required to be matched with the repetition frequency of the femtosecond pulse signal entering the stage.
Preferably, the two-port arm length difference is already lower than millimeter level when entering the last fiber coupler with higher repetition frequency, and is difficult to control by the tail fiber length difference, and the optical delay line 25 can be used for providing delay for the pulse signal, so as to obtain the femtosecond pulse laser with 1064nm wave band and THz high repetition frequency.
Further, the pre-amplifying section 37 includes a first stage pre-amplifying section and a second stage pre-amplifying section, the first stage pre-amplifying section includes a third wavelength division multiplexer 29, a third single-mode pump laser 57 and a driving circuit thereof, a first ytterbium-doped gain fiber 30, and a second optical isolator 31, an input end of the third wavelength division multiplexer 29 is connected to an output end of the frequency boosting section 27 and the third single-mode pump laser 57 and the driving circuit thereof, and an output end of the third wavelength division multiplexer 29 is connected to the second optical isolator 31 through the first ytterbium-doped gain fiber 30; the second stage pre-amplifying section comprises a fourth wavelength division multiplexer 33, a fourth single-mode pump laser 32 and a driving circuit thereof, a second ytterbium-doped gain fiber 35 and a third optical isolator 36, wherein the input end of the fourth wavelength division multiplexer 33 is connected to the output end of the first pre-amplifying section 37 and the fourth single-mode pump laser 32 and the driving circuit thereof, and the output end of the fourth wavelength division multiplexer 33 is connected to the third optical isolator 36 through the second ytterbium-doped gain fiber 35.
Further, the main amplifying section 50 includes a first stage main amplifying section and a second stage main amplifying section, the first stage main amplifying section includes a (2+1) x 1 optical combiner 40, a pair of multimode pump lasers 38, 39 and driving circuits thereof, a first double-clad ytterbium doped fiber 41 and a first high-power optical isolator 42, an input end of the (2+1) x 1 optical combiner 40 is connected to an output end of the second stage pre-amplifying section and a pair of multimode pump lasers 38, 39 and driving circuits thereof, and an output end of the (2+1) x 1 optical combiner 40 is connected to the first high-power optical isolator 42 through the first double-clad ytterbium doped fiber 41; the second stage main amplifying section comprises a (6+1) x 1 optical combiner 45, two groups of multimode pump lasers 43 and 44 and a driving circuit thereof, a second double-cladding ytterbium doped optical fiber 46, a pump leakage 47, a second high-power optical isolator 48 and an end cap 49, wherein the input end of the (6+1) x 1 optical combiner 4545 is connected to the output end of the first stage main amplifying section and the two groups of multimode pump lasers 43 and 44 and the driving circuit thereof, and the output end of the (6+1) x 1 optical combiner 45 is sequentially connected to the pump leakage, the second high-power optical isolator 48 and the end cap 49 through the second double-cladding ytterbium doped optical fiber 46. The pump leakage device is used for filtering residual pump light; the end cap 49 is used for expanding the output signal light to avoid damage to the end face of the optical fiber; the first high power optical isolator 42 and the second high power optical isolator 48 are used for unidirectional transmission of laser signals.
Specifically, the (2+1) ×1 optical fiber combiner and the (6+1) ×1 optical combiner 45 couple pump light of a multimode pump laser into the first and second double-clad ytterbium-doped fibers 41 and 46, and cause ytterbium-doped ions to transit, thereby amplifying signal light. The first high-power optical isolator 42 and the second high-power optical isolator can effectively control backward spontaneous emission amplification, improve output signal quality, and protect devices to a certain extent.
Further, the pulse width compressing part 56 includes a collimator mirror 51, a pair of diffraction gratings 53, 54, a reflector 55, and an output mirror 52, where the pair of diffraction gratings 53, 54 is used to compress the output high-power femtosecond pulse laser signal, so as to realize the laser pulse signal output of narrower pulses; after passing through the collimator lens 51, the laser signal is compressed by the diffraction grating pairs 53 and 54 and the reflecting mirror 55, and then output through the output lens 52.
The invention has the following advantages: 1. according to the invention, one end of the optical reflector 1 is connected with the reflection input end of the first wavelength division multiplexer 10 directly through the first erbium-doped gain fiber 2, and the signal output end of the first wavelength division multiplexer 10 is connected with the first collimator through a section of short tail fiber, so that the cavity length of the resonant cavity of the seed source 13 of the erbium-doped fiber laser is effectively reduced. 2. According to the invention, the erbium-doped fiber laser is adopted to lock the mode to generate the femtosecond pulse seed source with 1550nm wave band, so that the complexity of dispersion compensation when the ytterbium-doped fiber is adopted as the seed source is avoided, and the laser signal with 1064nm wave band is simply obtained through a section of high-nonlinearity fiber 19. 3. The femtosecond seed source of the erbium-doped fiber laser adopts shorter resonant cavity length, so that the number of cascaded fiber couplers of the frequency lifting part 27 can be reduced. 4. The invention adopts the optical delay line 25 to replace the tail fiber length difference when approaching to the THz repetition frequency, thereby realizing the THz high repetition frequency femtosecond pulse laser output. 4. The invention adopts MOPA structure of two-stage pre-amplifying part 37 and two-stage main amplifying part 50, and can well control nonlinear effect to realize high-power femtosecond pulse laser output. 5. The all-optical fiber packaging and modularization of the components of the invention lead the whole system to have compact structure, less insertion loss and high system reliability.
In the above-mentioned high repetition rate high power femtosecond fiber laser 100 based on the scattered wave, the seed source 13 of erbium-doped fiber laser is used to generate the femtosecond pulse signal with higher repetition rate, the signal is amplified and then passed through the nonlinear frequency conversion of a section of high nonlinear fiber 19, and then passed through the multistage frequency lifting part 27 formed by the coupler to obtain the femtosecond pulse signal with high repetition rate of THz, and then passed through the MOPA structure of the pre-amplifying part 37 of ytterbium-doped fiber and the main amplifying part 50 of two-stage ytterbium-doped double-clad fiber, the low power high repetition rate femtosecond pulse signal is amplified to the laser signal output of tens of watts, and the laser signal is subjected to the extra-cavity pulse width compression, so as to obtain the high power laser signal output with high repetition rate of THz. The method has the advantages of simple installation structure, easy realization, low cost and convenient popularization.
It should be noted that the above-mentioned embodiments are merely preferred embodiments of the present invention, and are not intended to limit the present invention, but various modifications and variations of the present invention will be apparent to those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (8)
1. The THz high repetition frequency high power femtosecond fiber laser based on the dispersion wave is characterized by comprising an erbium-doped fiber laser seed source, a frequency lifting part, an amplifying part and a pulse width compressing part; the output end of the seed source of the erbium-doped fiber laser is connected with the frequency lifting part through a high nonlinear fiber, the output end of the frequency lifting part is connected to the amplifying part, the amplifying part comprises a pre-amplifying part and a two-stage main amplifying part, and the output end of the amplifying part is connected with the pulse width compressing part; the laser signal generated by the erbium-doped fiber laser seed source is subjected to nonlinear frequency conversion by the high nonlinear fiber and is subjected to frequency lifting to THz high repetition frequency by the frequency lifting part, the THz high repetition frequency laser signal is subjected to power amplification by the pre-amplification part and the two-stage main amplification part of the amplification part and then is subjected to pulse width compression part to output a THz high repetition frequency high-power femtosecond pulse signal, the erbium-doped fiber laser seed source comprises a laser seed source and an erbium-doped fiber amplification part, and the laser seed source comprises an optical reflector, a first erbium-doped gain fiber, a first wavelength division multiplexer and a first optical isolator which are sequentially connected; the two input ends of the first wavelength division multiplexer are respectively connected with the first erbium-doped gain optical fiber and the output end of the first single-mode pump laser and the output end of the driving circuit of the first single-mode pump laser, the two output ends of the first wavelength division multiplexer are respectively connected with the first optical isolator and the input end of the saturated absorber SESAM module, the frequency boosting part comprises cascaded 50/50 optical fiber couplers, the cascaded 50/50 optical fiber couplers comprise a first 1×2 50/50 optical fiber coupler, a plurality of 2×2 50/50 optical fiber couplers and a second 1×2 50/50 optical fiber coupler which are sequentially connected, the first 1×2 50/50 optical fiber coupler and the plurality of 2×2 50/50 optical fiber couplers are connected by optical fibers, and the plurality of 2×2 50/50 optical fiber couplers and the second 1×2 50/50 optical fiber coupler are connected by optical delay lines; the frequency lifting part adopts step-by-step frequency multiplication and is used for rapidly lifting the repetition frequency of the input laser signal.
2. The dispersive wave-based THz high repetition rate high power femtosecond fiber laser according to claim 1, wherein said first wavelength division multiplexer comprises a first fiber collimator, an optical filter, a polarizer, a wollaston prism and a second fiber collimator connected in sequence; the input end of the first fiber collimator is connected to the optical reflector through the first erbium-doped gain fiber.
3. The dispersive-wave-based THz high-repetition-frequency high-power femtosecond fiber laser according to claim 1, wherein the erbium-doped fiber amplifying part comprises a second wavelength division multiplexer, a second single-mode pump laser and a driving circuit thereof, and a second erbium-doped gain fiber, an input end of the second wavelength division multiplexer is connected to an output end of the first optical isolator and an output end of the second single-mode pump laser and a driving circuit thereof, an output end of the second wavelength division multiplexer is connected to a second erbium-doped gain fiber, and the erbium-doped fiber amplifying part is used for boosting an output power of the seed source of the erbium-doped fiber laser.
4. A dispersive wave-based THz high repetition rate high power femtosecond fiber laser according to claim 3, wherein an input end of the high nonlinearity fiber is connected to the second erbium doped gain fiber, an output end of the high nonlinearity fiber is connected to the frequency boost section, and the high nonlinearity fiber is used for performing nonlinear frequency conversion on an input laser signal.
5. The dispersive wave-based THz high repetition frequency high power femtosecond fiber laser according to claim 1, wherein the pre-amplification part comprises a first stage pre-amplification part and a second stage pre-amplification part, the first stage pre-amplification part comprises a third wavelength division multiplexer, a third single-mode pump laser and a driving circuit thereof, a first ytterbium-doped gain fiber and a second optical isolator, an input end of the third wavelength division multiplexer is connected to an output end of the frequency boosting part and the third single-mode pump laser and the driving circuit thereof, and an output end of the third wavelength division multiplexer is connected to the second optical isolator through a first ytterbium-doped gain fiber; the second-stage pre-amplification part comprises a fourth wavelength division multiplexer, a fourth single-mode pump laser and a driving circuit thereof, a second ytterbium-doped gain optical fiber and a third optical isolator, wherein the input end of the fourth wavelength division multiplexer is connected to the output end of the first-stage pre-amplification part, the fourth single-mode pump laser and the driving circuit thereof, and the output end of the fourth wavelength division multiplexer is connected to the third optical isolator through the second ytterbium-doped gain optical fiber.
6. The dispersive wave-based THz high repetition rate high power femtosecond fiber laser according to claim 5, wherein the main amplifying section comprises a first stage main amplifying section and a second stage main amplifying section, the first stage main amplifying section comprises a (2+1) x 1 optical combiner, a pair of multimode pump lasers and driving circuits thereof, a first double-clad ytterbium-doped fiber and a first high power optical isolator, an input end of the (2+1) x 1 optical combiner is connected to an output end of the second stage pre-amplifying section and a pair of multimode pump lasers and driving circuits thereof, and an output end of the (2+1) x 1 optical combiner is connected to the first high power optical isolator through the first double-clad ytterbium-doped fiber; the second-stage main amplifying part comprises a (6+1) x 1 optical combiner, two groups of multimode pump lasers and driving circuits thereof, a second double-cladding ytterbium-doped optical fiber, a pump leakage device, a second high-power optical isolator and an end cap, wherein the input end of the (6+1) x 1 optical combiner is connected to the output end of the first-stage main amplifying part and the two groups of multimode pump lasers and driving circuits thereof, and the output end of the (6+1) x 1 optical combiner is sequentially connected to the pump leakage device, the second high-power optical isolator and the end cap through the second double-cladding ytterbium-doped optical fiber.
7. The dispersive wave-based THz high repetition rate high power femtosecond fiber laser of claim 6, wherein the pump leakage is used to filter out the remaining pump light; the end cap is used for expanding the beam of the output signal light so as to avoid damage to the end face of the optical fiber; the first high-power optical isolator and the second high-power optical isolator are used for unidirectional transmission of laser signals.
8. The dispersive wave-based THz high repetition rate high power femtosecond fiber laser according to claim 1, wherein the pulse width compression part comprises a collimator mirror, a diffraction grating pair, a reflector mirror and an output mirror, and the diffraction grating pair is used for compressing the output high power femtosecond pulse laser signal to realize the laser pulse signal output of narrower pulses; after passing through the collimating mirror, the laser signal is compressed by the diffraction grating pair and the reflecting mirror, and then is output through the output mirror.
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| CN109616857A (en) * | 2018-12-05 | 2019-04-12 | 光越科技(深圳)有限公司 | Sub- THz high power picosecond optical fiber laser based on MOPA structure |
| CN109286121B (en) * | 2018-12-06 | 2024-01-05 | 光越科技(深圳)有限公司 | Mode-locked fiber laser based on space division multiplexing SESAM module |
| CN109361146A (en) * | 2018-12-24 | 2019-02-19 | 光越科技(深圳)有限公司 | The ultrashort pulse fiber laser seed source system adjusted based on singlechip feedbsck |
| CN109787081B (en) * | 2019-01-23 | 2021-08-03 | 广东朗研科技有限公司 | Intermediate infrared ultrashort pulse laser light source |
| CN109742644A (en) * | 2019-03-11 | 2019-05-10 | 安徽天琢激光科技有限公司 | A kind of high power column vector optical fiber laser |
| CN114720947B (en) * | 2022-06-07 | 2022-10-04 | 浙江大学 | Terahertz radar detection method and system based on photon frequency doubling technology |
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