CN211265955U

CN211265955U - Adjustable ultra-high repetition frequency ultra-short pulse fiber laser

Info

Publication number: CN211265955U
Application number: CN202020044870.XU
Authority: CN
Inventors: 王天褀; 丁颖; 李对对; 孙志培; 任兆玉
Original assignee: Northwestern University
Current assignee: Northwestern University
Priority date: 2020-01-09
Filing date: 2020-01-09
Publication date: 2020-08-14
Anticipated expiration: 2030-01-09

Abstract

The utility model provides an adjustable super high repetition frequency ultrashort pulse fiber laser, fiber laser includes: the optical fiber laser comprises a pumping source, a wavelength division multiplexer, a single-mode optical fiber, a gain optical fiber, a saturable absorber and an M-Z sub-cavity, wherein the single-mode optical fiber, the gain optical fiber, the M-Z sub-cavity and the saturable absorber are connected to form an annular optical fiber laser cavity, and the pumping source is coupled to the annular optical fiber laser cavity through the wavelength division multiplexer. Fiber laser has realized for the first time that repetition frequency is at the ultrashort pulse laser output of 31.81fs of high repetition frequency above 11.11THz and pulse width, has improved an order of magnitude than the highest repetition frequency known at present, and the monolithic device structure simple manufacture, low cost has extensive popularization and application and worth moreover.

Description

Adjustable ultra-high repetition frequency ultra-short pulse fiber laser

Technical Field

The utility model relates to a fiber laser technical field, concretely relates to adjustable super high repetition frequency ultrashort pulse fiber laser.

Background

With the rapid development of fiber lasers and laser technologies, people have higher and higher performance requirements on fiber lasers, and in order to meet the increasing demands of different fields, fiber lasers gradually form different research directions and are mainly divided into high-power fiber lasers, multi-wavelength fiber lasers, ultra-short pulse fiber lasers, wide-spectrum fiber lasers and high-repetition-frequency fiber lasers. At present, we have made more intensive research and good results on high-power fiber lasers and the like, but have a larger development space for high-frequency fiber lasers. The continuous ultrahigh frequency pulse sequence has irreplaceable important functions in many fields, for example, the continuous ultrahigh frequency pulse sequence can be used in the fields of ultrahigh bit rate optical communication networks, all optical logic and signal processing circuits and testing and measuring systems, microwave photonics and nonlinear optics, arbitrary optical waveform generation, time-resolved double-optical-comb spectrum, ultrafast asynchronous optical sampling, high-precision time-frequency metering, astronomical optical-comb spectrometer calibration, biological imaging and the like. More importantly, for future computer processors with clock frequencies above the electrical limit, it becomes important how to achieve higher and higher repetition frequencies. At present, two methods for generating high repetition frequency laser are mainly used, namely a Fabry-Perot (F-P) sub-cavity and an optical fiber micro-ring sub-cavity are respectively inserted into an optical fiber laser. The F-P cavity is used for generating high repetition frequency laser, the repetition frequency can be adjusted by adjusting the distance between the F-P cavity mirrors, and the repetition frequency generated by the closer the distance between the cavity mirrors is higher. However, the distance between the cavity mirrors is continuously shortened, the power density of light oscillating back and forth between the cavity mirrors is increased, and the cavity mirrors are easily damaged when the high-power laser output is required to be obtained, so that the high-repetition-frequency laser with higher power cannot be generated by the method. The optical fiber micro-ring cavity is used for generating high repetition frequency laser, and the smaller the radius of the micro-ring, the higher the repetition frequency is obtained. However, the radius of the micro-ring cannot be adjusted after the micro-ring is prepared, so that the repetition frequency of the obtained laser cannot be adjusted, the higher the repetition frequency is, the smaller the radius of the micro-ring is required to be, and the manufacturing difficulty is correspondingly increased. Therefore, the devices for generating ultra-high repetition frequency ultra-short pulse laser in the prior art have certain defects, and the practical application of the devices is limited.

SUMMERY OF THE UTILITY MODEL

The utility model discloses based on above-mentioned prior art problem, the utility model provides an adjustable super high repetition frequency ultrashort pulse fiber laser ware, through producing high repetition frequency laser with M-Z sub-chamber in coordination based on the saturable absorber of two-dimensional material, make only through adjusting the repetition frequency of length difference just adjustable production laser between the sub-chamber two arms of M-Z, the repetition frequency that length difference is less available is just higher just, and even power is higher, entire system also can the steady operation, can not cause the device to damage, and realized for the first time that repetition frequency is at the high repetition frequency more than 11.11THz and the ultrashort pulse laser output of pulse width at 31.81fs, improved an order of magnitude than the highest repetition frequency known at present, and the whole device structure simple manufacture, therefore, the carrier wave prepaid electric energy meter is low in cost, and has extensive popularization and application value.

The utility model provides a technical scheme as follows that above-mentioned technical problem took:

a tunable ultra-high repetition frequency ultra-short pulse fiber laser, comprising: the optical fiber laser comprises a pumping source, a wavelength division multiplexer, a single-mode optical fiber, a gain optical fiber, a saturable absorber and an M-Z sub-cavity, wherein the single-mode optical fiber, the gain optical fiber, the M-Z sub-cavity and the saturable absorber are connected to form an annular optical fiber laser cavity, and the pumping source is coupled to the annular optical fiber laser cavity through the wavelength division multiplexer.

Further in accordance with the present invention, the tunable ultra-high repetition frequency ultra-short pulse fiber laser, wherein the M-Z sub-cavity comprises a first optical coupler 7, a second optical coupler 10, a first optical fiber arm, a second optical fiber arm, a first polarization controller 8 and a light delayer 9, the first optical coupler 7 has a first input end, a first output end and a second output end, the second optical coupler 10 has a first input end, a second input end, a first output end and a second output end, the first input end of the first optical coupler 7 is connected to the single-mode fiber of the ring-shaped fiber laser cavity, the first output end of the first optical coupler 7 is connected to one end of the first optical fiber arm, the other end of the first optical fiber arm is connected to the first input end of the second optical coupler 10, the first polarization controller 8 is disposed on the first optical fiber arm, the second output end of the first optical coupler 7 is connected to one end of a second optical fiber arm, the other end of the second optical fiber arm is connected to the second input end of a second optical coupler 10, the optical delayer 9 is arranged on the second optical fiber arm, the first output end of the second optical coupler 10 is connected to the single-mode fiber of the ring-shaped fiber laser cavity, and the second output end of the second optical coupler 10 serves as the output end of the ring-shaped fiber laser cavity.

Further in accordance with the present invention, said tunable ultra-high repetition frequency ultra-short pulse fiber laser, wherein said first optical coupler 7 is a 1 × 2 optical coupler, and the output coupling ratio of the first output end and the second output end is 40% to 60%; the second optical coupler 10 is a 2 × 2 optical coupler, and the input coupling ratio of the first input end and the second input end and the output coupling ratio of the first output end and the second output end are both 50% to 50%, and the first optical fiber arm and the second optical fiber arm are both single-mode optical fibers.

Further basis adjustable superelevation repetition frequency ultrashort pulse optical fiber laser, wherein light delayer includes income light end 21, light-emitting end 22 and speculum 23, go into light end 21 and light-emitting end 22 connect in second optic fibre arm, speculum 23 will warp the light beam reflection of income light end incident to light-emitting end, just speculum 23's position is adjustable.

Further according to adjustable super high repetition frequency ultrashort pulse fiber laser, wherein saturable absorber includes first optic fibre jumper wire head, second optic fibre jumper wire head, graphite alkene film and flange, the butt fusion has single mode fiber in first optic fibre jumper wire head and the second optic fibre jumper wire head, graphite alkene film set up in between first optic fibre jumper wire head and the second optic fibre jumper wire head, and the single mode fiber end face that is located first optic fibre jumper wire head hugs closely in a side surface of graphite alkene film, and the single mode fiber end face that is located second optic fibre jumper wire head hugs closely in graphite alkene film's opposite side surface, first optic fibre jumper wire head and second optic fibre jumper wire head pass through flange connects.

Further according to the utility model discloses an adjustable super high repetition frequency ultrashort pulse fiber laser, wherein graphene film's thickness is 3-8 microns, and the luminousness is 60-90%, and the graphite number of layers that contains is 1-30 layers.

Further according to the utility model discloses a tunable ultra-high repetition frequency ultrashort pulse fiber laser, wherein the pumping source includes first pumping source 1 and second pumping source 5, wavelength division multiplexer includes first wavelength division multiplexer 2 and second wavelength division multiplexer 4, first pumping source 1 warp first wavelength division multiplexer couples in the annular fiber laser cavity, second pumping source 5 warp second wavelength division multiplexer couples in the annular fiber laser cavity, the gain fiber set up in between first wavelength division multiplexer 2 and second wavelength division multiplexer 4.

Further according to adjustable super high repetition frequency ultrashort pulse fiber laser, wherein still include optical isolator 6 and second polarization controller 12, optical isolator 6 set up in between second wavelength division multiplexer and the first optical coupler 7, saturable absorber 11 set up in between first wavelength division multiplexer and the second optical coupler 10, second polarization controller 12 set up in between saturable absorber 11 and the second optical coupler 10.

Further according to the present invention, the tunable ultra-high repetition frequency ultra-short pulse fiber laser further comprises a third optical coupler 13, wherein the third optical coupler 13 has a first input end, a first output end and a second output end, the first input end of the third optical coupler 13 is connected to the second output end of the second optical coupler 10.

Further according to the present invention, the tunable ultra-high repetition frequency ultra-short pulse fiber laser further comprises a spectrometer 14 and an autocorrelator 15, wherein the spectrometer 14 is connected to the first output end of the third optical coupler 13, and the autocorrelator 15 is connected to the second output end of the third optical coupler 13.

Through the technical scheme of the utility model can reach following innovation technological effect at least:

1) the utility model discloses use two-dimensional material (graphite alkene, black scale, MoS) for the first time₂Etc. and SESAM) as a saturable absorber and combined with the M-Z sub-cavity structure to generate ultra-high repetition frequency and ultra-short pulse laser output based on the synergistic effect in the annular fiber laser resonant cavity, and provides an ultra-high repetition frequency and ultra-short pulse laser generating device with a brand-new structure;

2) the utility model discloses combine Mach-Zehnder (M-Z) sub-chamber in the annular optical fiber laser cavity for the first time, and adjust the repetition frequency of produced laser through adjusting the length difference between M-Z sub-chamber two arms, the smaller the length difference can be obtained the repetition frequency just higher, and repetition frequency is adjustable between 0.1 ~ 11.11THz, and even power is higher, whole system also can steady operation, can not cause the device to damage, and realized for the first time that repetition frequency is at the high repetition frequency above 11.11THz and the ultrashort pulse laser output of pulse width at 31.fs 81, the highest repetition frequency that has known at present has improved an order of magnitude;

3) the device overall structure simple manufacture, low cost can be used as the THz radiation excitation source that produces wavelength adjustable, has extensive popularization application prospect.

Drawings

Fig. 1 is a schematic diagram of the structure of the tunable ultra-high repetition frequency ultra-short pulse fiber laser according to the present invention;

fig. 2 is a schematic structural diagram of an optical delay timer in the optical fiber laser according to the present invention;

fig. 3 is a schematic structural diagram of a saturable absorber in the fiber laser of the present invention.

The meanings of the reference symbols in the figures are as follows:

1-a first pump source, 2-a first wavelength division multiplexer, 3-a gain fiber, 4-a second wavelength division multiplexer, 5-a second pump source, 6-an optical isolator, 7-a first optical coupler, 8-a first polarization controller, 9-an optical delayer, 10-a second optical coupler, 11-a saturable absorber, 12-a second polarization controller, 13-a third optical coupler, 14-a spectrometer, 15-an autocorrelator, 16-a first fiber jumper, 17-a second fiber jumper, 18-a connecting flange, 19-a graphene film, 20-a single mode fiber, 21-an optical input end, 22-an optical output end and 23-a reflector.

Detailed Description

The technical solutions of the present invention are described in detail below with reference to the accompanying drawings so as to enable those skilled in the art to more clearly understand the present invention, but the protection scope of the present invention is not limited thereby.

The utility model discloses introduce the annular fiber laser with two-dimensional material as saturable absorber and be used for producing ultrashort light pulse and high repetition frequency laser in, at first, the description is as the utility model discloses well saturable absorber's two-dimensional material. The utility model discloses in adopt the two-dimensional material as saturable absorber, put into the method in the fiber laser of M-Z structure as the subchamber and produce high repetition frequency laser. The two-dimensional material has excellent optical, electrical and chemical characteristics, is generally applied to the fields of ultrafast photonics and nonlinear photonics, and can realize high repetition frequency modulation of laser and generate ultra-high repetition frequency ultrashort pulse output based on the saturable absorption characteristic and nonlinear optical characteristic manufactured by the two-dimensional material when being placed in a laser resonant cavity. In a two-dimensional material, graphene has a unique zero-band-gap linear energy band structure, so that photons with any wavelength can be absorbed by the graphene, and in addition, ultra-strong carrier band-to-band transition and an ultra-fast relaxation process enable the graphene to be used as an ideal saturable absorber for generating ultra-short light pulses and high repetition frequency laser.

The utility model discloses an in the concrete embodiment preferred adoption graphite alkene two-dimensional material as saturable absorber, graphite alkene two-dimensional material wherein has film structure, and film thickness 3-8 microns, preferred 5 microns, the luminousness 60-90% of film, preferred 62.8%, the graphite alkene number that the film contains is 1-30 layers, preferred 20 layers graphite alkene that contain.

The utility model discloses a fibre-optic laser based on two-dimensional material produces adjustable super high repetition frequency ultrashort pulse laser with M-Z sub-cavity synergism is specific as shown in figure 1, including first pump source 1, first wavelength division multiplexer 2, gain optic fibre 3, second wavelength division multiplexer 4, second pump source 5, optical isolator 6, first optical coupler 7, first polarization controller 8, optical delay 9, second optical coupler 10, saturable absorber 11, second polarization controller 12, third optical coupler 13, spectrum appearance 14 and autocorrelator 15, as the light path diagram shown in figure 1, the utility model discloses use ordinary Single Mode Fiber (SMF) to prepare an annular fiber laser cavity, then add M-Z in the annular cavity in order to realize the acquisition of high repetition frequency sub-cavity laser, the total length of annular laser cavity is about 8M, and the length of M-Z sub-cavity needs to be far more than the length of operating wavelength, since the working wavelength of the common laser is in the micron or submicron order, the length of the M-Z sub-cavity in practical operation generally meets the condition. The first pump source 1 and the second pump source 5 respectively adopt continuous lasers, as a preferred embodiment of the present invention, two continuous lasers with working wavelength preferably being 980nm are used as the first pump source 1 and the second pump source 5, the pump laser is coupled into the ring-shaped optical fiber laser cavity through two Wavelength Division Multiplexers (WDM), namely a first wavelength division multiplexer 2 and a second wavelength division multiplexer 4, respectively, a gain optical fiber 3 with length preferably being 1.4m is added between the two WDM, the gain fiber 3 is preferably a highly doped erbium-doped fiber (EDF) with an operating wavelength of 1550nm, and 980nm pump laser coupled into the ring cavity pumps and excites the EDF to generate fiber laser oscillation, preferably matching the operating wavelength of 1550nm of the highly doped erbium-doped fiber with the operating wavelength of 980nm of the corresponding pump source, the working wavelength of the first wavelength division multiplexer and the working wavelength of the second wavelength division multiplexer are selected to be 980nm/1550 nm. Further, an optical Isolator (ISO)6 with the working wavelength of 1550nm is added into the annular laser cavity to ensure unidirectional transmission of light. The utility model discloses what innovated introduces mach-zehnder sub-cavity in annular optic fibre laser cavity and is M-Z sub-cavity, and specific M-Z sub-cavity of constituteing through first optical coupler 7, second optical coupler 10 and two sections single mode fiber, wherein first optical coupler 7 is a 1 x 2 Optical Coupler (OC), and the coupling ratio of two outputs 40%: 60%; the second optical coupler 10 is a 2 × 2 optical coupler OC having a coupling ratio of 50% to 50%; a 40% coupling end of the first optical coupler 7 is connected to a first coupling input end of the second optical coupler 10 through a first single-mode optical fiber, and the first single-mode optical fiber is provided with a first polarization controller 8 which jointly forms a first arm of the M-Z sub cavity; and the 60% coupling end of the first optical coupler 7 is connected to the second coupling input end of the second optical coupler 10 through a second single-mode optical fiber, the second single-mode optical fiber is connected with an optical delayer 9 to jointly form a second arm of the M-Z sub-cavity, and the optical path difference between the first arm and the second arm of the M-Z sub-cavity is changed through the optical delayer 9 so as to meet the working condition of the M-Z sub-cavity. To match the operating wavelength of the preferred highly erbium doped fiber 1550nm, the operating wavelengths of the first and second

optical couplers

7 and 10 are both around 1550 nm. The utility model discloses be provided with optical time delayer 9(OTDL) on the second arm of M-Z sub chamber, because optical time delayer OTDL has about 1.8 dBm's insertion loss near 1550nm wave band, consequently in order to guarantee that the light intensity of two arms of M-Z sub chamber is close, select to connect this second arm in the 60% coupling output of first optical coupler 7 to compensate optical time delayer OTDL's insertion loss through this arm 60% coupling. The utility model discloses a light delayer changes the optical distance of light in this arm, and then changes the optical distance difference between first arm and the second arm, light delayer structure as shown in figure 2, including going into light end 21, light-emitting end 22 and speculum 23, speculum 23 can carry out the translation for plane mirror and its position, and no matter which position is arrived in the speculum translation, goes into the light beam of light end incident and is reflected to light-emitting end output behind speculum 23. The light inlet end 21 and the light outlet end 22 are respectively coupled to the single-mode fiber of the second arm of the M-Z sub-cavity, light from the single-mode fiber enters from the light inlet end, is reflected by the reflector, is output from the light outlet end 22 and is coupled to the single-mode fiber, the transmission distance of the light in the single-mode fiber can be changed by adjusting the position of the reflector 23, and further, the optical path of the light in the second arm of the M-Z sub-cavity is changed. In addition, the adjusting range of the OTDL is 10cm, so that the length difference of the two-arm optical fibers of the M-Z sub-cavity is within the optical path of 0-10 cm to ensure that the OTDL can achieve the required adjusting effect. A Polarization Controller (PC) added to the first arm of the M-Z subcavity can be used to adjust the polarization state of that arm. The two output ends of the second optical coupler 10 are also coupled and output in a ratio of 50%: 50 percent of the output end of the coupler is led out of the ring cavity and is connected with the spectrometer 14 and/or the autocorrelator 15 to monitor the spectrum signal or the pulse signal. The other end is coupled to the single-mode fiber in the annular fiber laser cavity, a second polarization controller 12 is arranged on the single-mode fiber in the annular laser cavity, and the second polarization controller 12 and the first polarization controller 8 in the M-Z sub cavity respectively adjust the polarization states in the annular fiber laser cavity and the M-Z sub cavity.

The utility model provides a saturable absorber includes first optic fibre jumper head, second optic fibre jumper head, graphite alkene film and flange, as shown in figure 3, the butt fusion has single mode fiber in first optic fibre jumper head and the second optic fibre jumper head, graphite alkene film set up in between first optic fibre jumper head and the second optic fibre jumper head, and the single mode fiber end face that is located first optic fibre jumper head hugs closely in a side surface of graphite alkene film, and the single mode fiber end face that is located second optic fibre jumper head hugs closely in the opposite side surface of graphite alkene film, first optic fibre jumper head and second optic fibre jumper head pass through flange connects. Preferably, the first optical fiber jumper head and the second optical fiber jumper head are externally threaded at the outer sides of the front ends, and the flange has a sleeve structure and is internally threaded at the inner side of the sleeve. The utility model discloses a this kind of innovation structure will be as the graphene film of two-dimensional material to combine in the annular optical fiber laser cavity.

The utility model discloses the innovation adds the M-Z sub chamber in the annular optical fiber laser cavity to use the graphite alkene film as saturable absorber, finally obtain the output of high repetition frequency ultrashort pulse laser. The research result of the multiple repetition test shows, the technical scheme of the utility model the repetition frequency of laser can realize continuous regulation in a large scale through adjusting optical time delay ware OTDL to along with repetition frequency's improvement, laser pulse width also constantly reduces, and this is the advantage that uses little ring cavity and F-P subchamber to produce high repetition frequency laser and not possess among the prior art. Finally based on the technical scheme of the utility model pass through the optical time delay device OTDL and change the optical path difference of two arms of M-Z sub chamber, can obtain the high repetition frequency that repetition frequency reaches 11.11THz, the ultrashort pulse laser that pulse width is 31.81fs, have wide popularization application prospect.

The above description is only for the preferred embodiment of the present invention, and the technical solution of the present invention is not limited thereto, and any known modifications made by those skilled in the art on the basis of the main technical idea of the present invention belong to the technical scope to be protected by the present invention, and the specific protection scope of the present invention is subject to the description of the claims.

Claims

1. An adjustable ultra-high repetition frequency ultra-short pulse fiber laser is characterized by comprising: the optical fiber laser comprises a pumping source, a wavelength division multiplexer, a single-mode optical fiber, a gain optical fiber, a saturable absorber and an M-Z sub-cavity, wherein the single-mode optical fiber, the gain optical fiber, the M-Z sub-cavity and the saturable absorber are connected to form an annular optical fiber laser cavity, and the pumping source is coupled to the annular optical fiber laser cavity through the wavelength division multiplexer.

2. The tunable ultra-high repetition frequency ultra-short pulse fiber laser according to claim 1, wherein the M-Z sub-cavity comprises a first optical coupler (7), a second optical coupler (10), a first fiber arm, a second fiber arm, a first polarization controller (8) and a light delayer (9), the first optical coupler (7) has a first input end, a first output end and a second output end, the second optical coupler (10) has a first input end, a second input end, a first output end and a second output end, the first input end of the first optical coupler (7) is connected to a single-mode fiber of the ring-shaped fiber laser cavity, the first output end of the first optical coupler (7) is connected to one end of the first fiber arm, the other end of the first fiber arm is connected to the first input end of the second optical coupler (10), the first polarization controller (8) is disposed on the first fiber arm, the second output end of the first optical coupler (7) is connected to one end of a second optical fiber arm, the other end of the second optical fiber arm is connected to the second input end of a second optical coupler (10), the optical delayer (9) is arranged on the second optical fiber arm, the first output end of the second optical coupler (10) is connected to a single-mode optical fiber of the ring-shaped optical fiber laser cavity, and the second output end of the second optical coupler (10) serves as the output end of the ring-shaped optical fiber laser cavity.

3. The tunable ultra-high repetition frequency ultra-short pulse fiber laser according to claim 2, characterized in that the first optical coupler (7) is a 1 x 2 optical coupler, and the output coupling ratio of the first output end and the second output end is 40%: 60%; the second optical coupler (10) is a 2 x 2 optical coupler, the input coupling ratio of the first input end and the second input end and the output coupling ratio of the first output end and the second output end are both 50% to 50%, and the first optical fiber arm and the second optical fiber arm are both single-mode optical fibers.

4. The tunable ultra-high repetition frequency ultrashort pulse fiber laser as claimed in claim 2, wherein the optical delayer comprises an optical input end (21), an optical output end (22) and a mirror (23), the optical input end (21) and the optical output end (22) are connected to the second fiber arm, the mirror (23) reflects the light beam incident through the optical input end to the optical output end, and the position of the mirror (23) is adjustable.

5. The tunable ultra-high repetition frequency ultra-short pulse fiber laser device according to any one of claims 1 to 4, wherein the saturable absorber includes a first fiber jumper head, a second fiber jumper head, a graphene film and a connecting flange, the first fiber jumper head and the second fiber jumper head are internally welded with single-mode fibers, the graphene film is disposed between the first fiber jumper head and the second fiber jumper head, the end face of the single-mode fiber located in the first fiber jumper head is tightly attached to one side surface of the graphene film, the end face of the single-mode fiber located in the second fiber jumper head is tightly attached to the other side surface of the graphene film, and the first fiber jumper head and the second fiber jumper head are connected through the connecting flange.

6. The tunable ultra-high repetition frequency ultra-short pulse fiber laser as claimed in claim 5, wherein the graphene film has a thickness of 3-8 μm, a light transmittance of 60-90%, and 1-30 graphene layers.

7. The tunable ultra-high repetition frequency ultrashort pulse fiber laser of claim 2, wherein the pump source comprises a first pump source (1) and a second pump source (5), the wavelength division multiplexer comprises a first wavelength division multiplexer (2) and a second wavelength division multiplexer (4), the first pump source (1) is coupled to the ring fiber laser cavity via the first wavelength division multiplexer, the second pump source (5) is coupled to the ring fiber laser cavity via the second wavelength division multiplexer, and the gain fiber is disposed between the first wavelength division multiplexer (2) and the second wavelength division multiplexer (4).

8. The tunable ultra-high repetition frequency ultrashort pulse fiber laser of claim 7, further comprising an optical isolator (6) and a second polarization controller (12), wherein the optical isolator (6) is disposed between the second wavelength division multiplexer and the first optical coupler (7), the saturable absorber (11) is disposed between the first wavelength division multiplexer and the second optical coupler (10), and the second polarization controller (12) is disposed between the saturable absorber (11) and the second optical coupler (10).

9. The tunable ultra-high repetition frequency ultrashort pulse fiber laser according to claim 2, further comprising a third optical coupler (13), the third optical coupler (13) having a first input end, a first output end and a second output end, the first input end of the third optical coupler (13) being connected to the second output end of the second optical coupler (10).

10. The tunable ultra-high repetition frequency ultrashort pulse fiber laser according to claim 9, further comprising a spectrometer (14) and an autocorrelator (15), the spectrometer (14) being connected to the first output of the third optical coupler (13), the autocorrelator (15) being connected to the second output of the third optical coupler (13).