CN110994342A - Mode-locked fiber laser based on dual-wavelength fiber Bragg grating - Google Patents

Mode-locked fiber laser based on dual-wavelength fiber Bragg grating Download PDF

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CN110994342A
CN110994342A CN201911355766.0A CN201911355766A CN110994342A CN 110994342 A CN110994342 A CN 110994342A CN 201911355766 A CN201911355766 A CN 201911355766A CN 110994342 A CN110994342 A CN 110994342A
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wavelength
dual
bragg grating
fiber bragg
fiber
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张磊
姜华卫
付小虎
赵儒臣
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Precilasers Co ltd
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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
    • H01S3/0675—Resonators including a grating structure, e.g. distributed Bragg reflectors [DBR] or distributed feedback [DFB] fibre lasers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/05—Construction or shape of optical resonators; Accommodation of active medium therein; Shape of active medium
    • H01S3/06—Construction or shape of active medium
    • H01S3/063—Waveguide lasers, i.e. whereby the dimensions of the waveguide are of the order of the light wavelength
    • H01S3/067—Fibre lasers
    • H01S3/06791—Fibre ring lasers
    • 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
    • H01S3/08—Construction or shape of optical resonators or components thereof
    • H01S3/08004—Construction or shape of optical resonators or components thereof incorporating a dispersive element, e.g. a prism for wavelength selection
    • 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
    • H01S3/10—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating
    • H01S3/11—Mode locking; Q-switching; Other giant-pulse techniques, e.g. cavity dumping
    • H01S3/1106—Mode locking
    • H01S3/1112—Passive mode locking
    • H01S3/1115—Passive mode locking using intracavity saturable absorbers

Abstract

A passive mode-locking fiber laser based on a dual-wavelength fiber Bragg grating comprises the dual-wavelength fiber Bragg grating, an active fiber, a pumping coupler, a pumping source, an output coupler and a saturable absorber. The invention takes the dual-wavelength fiber Bragg grating as the wavelength selection element in the resonant cavity of the laser, realizes the output of the high-stability dual-wavelength ultrashort pulse laser while keeping the advantages of simple and compact mode-locked fiber laser, easy manufacture, difficult environmental interference and the like, and has great development prospect and high application value.

Description

Mode-locked fiber laser based on dual-wavelength fiber Bragg grating
Technical Field
The invention relates to a fiber laser, in particular to a mode-locking fiber laser based on a dual-wavelength fiber Bragg grating.
Background
The mode-locked fiber laser has important application value in the fields of strong field physics, precision measurement, distance measurement, precision machining and the like by virtue of the advantages of narrow pulse width, high peak power, wide spectrum and the like of the output laser.
In general, the fiber laser obtains ultrashort pulse laser output by mode locking, and there are two ways:
firstly, actively locking the mold. An intensity or phase modulator is added in a resonant cavity of the laser, when the adjacent modulation time interval of the modulator is matched with the single oscillation time of the laser in the resonant cavity, a pulse can be selected in the cavity and continuously amplified and narrowed, the phase difference between different longitudinal modes is locked through periodic modulation, and finally the mode-locked pulse output with narrow pulse width is obtained. However, this method has the disadvantage that the pulse width of the output can be only in the order of nanoseconds due to the limited modulation rate and bandwidth of the modulator, and the existence of the modulator makes the overall structure of the laser bulky and complex (see Haus HA. mode-locking of lasers [ J ]. IEEE Journal of Selected Topics in quantum electronics,2000,6(6): 1173-1185.).
And secondly, passively locking the mode. A saturable absorber is added into a cavity, the light intensity of laser in the cavity is modulated by utilizing the characteristic that the absorption is larger when the light intensity is smaller and the absorption is smaller when the light intensity is larger, the part with the maximum light intensity is selected, the part with the maximum light intensity is amplified through stimulated radiation, the front edge and the rear edge of the part are continuously cut off, the pulse width is narrowed, and the phase difference between longitudinal modes is locked through periodic modulation, and finally the mode locking pulse output with ultra-short pulse width and ultra-high peak power (see Ippen E P. principles of passive mode locking [ J ]. Applied Physics B,1994,58(3): 159. 170.).
The dual-wavelength ultrashort pulse laser output realized by the mode-locked fiber laser can meet the requirements of the fields of dense wavelength division multiplexing systems, optical fiber sensing, optical fiber dispersion measurement and the like on light sources, and the application range of the mode-locked fiber laser can be further expanded. At present, the mode for realizing dual-wavelength laser output in the mode-locked fiber laser mainly comprises the following three modes:
firstly, adding a multi-wavelength Lyot filter based on laser polarization state and optical fiber dispersion into a laser resonant cavity, and realizing dual-wavelength laser output when the wavelength of two transmission peaks in the multi-wavelength filter can reach a laser threshold condition. However, this method has a problem that the transmission peak of the multi-wavelength Lyot filter has periodicity, and the specific wavelength and wavelength interval of the two-wavelength Laser cannot be precisely selected, so that it is difficult to meet the requirements of practical application { see Luo a P, Luo Z C, Xu W C, et.
And secondly, realizing dual-wavelength ultrashort pulse output by the combined action of complex nonlinear effect and dispersion in a resonant cavity of the mode-locked fiber laser. The method can obtain ultrashort pulse output with excellent performance at both wavelengths, but the method has the problems that the large amount of generated dual-wavelength laser depends on the nonlinear effect and dispersion in the resonant cavity, has certain randomness and is difficult to realize repeatedly, so that the method cannot meet the requirements of practical application { see Wang Y, Li J, Hong L, et.
And thirdly, nesting two mode-locked fiber lasers with different wavelengths, and improving the coherence of the ultrashort pulses with the two wavelengths by controlling the length of the shared fiber in the cavity and utilizing cross phase modulation to realize stable and efficient dual-wavelength ultrashort pulse output. However, this method usually requires a complex structure, and generally can only achieve dual-wavelength ultrashort pulse output with large wavelength interval { see Zeng J, Li B, Hao Q, et al.
Disclosure of Invention
The invention provides a passive mode-locking fiber laser based on a dual-wavelength fiber Bragg grating on the basis of the dual-wavelength mode-locking fiber laser technology, the dual-wavelength fiber Bragg grating and the passive mode locking are combined, stable and efficient dual-wavelength mode-locking pulse output is realized under the condition of ensuring the characteristics of short pulse width and high peak power of mode-locking pulse laser, and the addition of the dual-wavelength fiber Bragg grating does not damage the full-fiber structure of the laser, so that the characteristics of easy integration and high stability of the fiber laser are maintained. The laser also has the characteristics of simple and compact structure and easy manufacture, and can meet the application of the dual-wavelength mode-locking fiber laser in the fields of science, industry and the like.
The technical solution of the invention is as follows:
a passive mode-locking fiber laser based on dual-wavelength fiber Bragg grating is characterized in that: the dual-wavelength fiber Bragg grating optical fiber laser comprises a dual-wavelength fiber Bragg grating, an active fiber, a pump coupler, a pump source and a saturable absorber, wherein the dual-wavelength fiber Bragg grating is sequentially connected with the pump coupler, the active fiber and the saturable absorber in a fusion mode to form a linear cavity structure, and the 3 rd port of the pump coupler is connected with the pump source.
A passive mode-locking fiber laser based on dual-wavelength fiber Bragg grating is characterized in that: the dual-wavelength fiber Bragg grating optical fiber circulator is characterized in that light input from a port a can only be output from a port b, light input from the port b can only be output from the port c, the dual-wavelength fiber Bragg grating is connected with the port b of the circulator in a fusion manner so as to be added into a ring cavity, and a port e of the pump coupler is connected with an output port of the pump source.
The dual-wavelength fiber Bragg grating is characterized in that refractive index modulation with different periods is respectively introduced into the upper position and the lower position of the fiber core of the same section of optical fiber, so that two sub-fiber Bragg gratings with different reflection wavelengths are obtained in the same section of optical fiber, the two wavelengths can be reflected, and when the two wavelengths are both positioned in the gain bandwidth of the gain optical fiber, the high-efficiency and stable dual-wavelength ultrashort pulse laser output can be realized by matching with a saturable absorber.
The two sub-fiber Bragg gratings of the dual-wavelength fiber Bragg grating are respectively common fiber Bragg gratings with the same refractive index change period or chirped fiber Bragg gratings with the refractive index change period changing along the axial direction.
The reflectivity of the two sub-fiber Bragg gratings of the dual-wavelength fiber Bragg grating can be respectively in the range of 1-100%. When the reflectivity of one of the two sub fiber Bragg gratings is 100%, an output coupler needs to be inserted into the resonant cavity of the laser, wherein the output coupler can be a fused biconical taper beam splitter or a coating beam splitter and can output laser to the outside of the resonant cavity according to a certain proportion.
The active optical fiber is gain optical fiber doped with ytterbium, erbium, thulium or bismuth, or nonlinear optical fiber capable of generating stimulated Raman scattering, stimulated Brillouin scattering and optical parameter process.
The saturable absorber can be a true saturable absorber with a feedback function and based on a material absorption characteristic, such as a semiconductor saturable absorber mirror, a true saturable absorber without the feedback function and based on the material absorption characteristic, such as carbon nanotubes and graphene, an equivalent saturable absorber with the feedback function and based on a nonlinear effect in an optical fiber, such as a nonlinear optical ring mirror and a nonlinear amplification ring mirror, or an equivalent saturable absorber without the feedback function and based on the nonlinear effect in the optical fiber, such as nonlinear polarization rotation, as a key device for starting mode locking. The saturable absorber introduces periodic modulation through nonlinear absorption effect on the pulse to lock the phase difference between the longitudinal modes of the laser, and the absorption of the part with larger light intensity in the pulse is weaker, so that the loss of the part with larger light intensity after the pulse passes through the saturable absorber is smaller, the part with the maximum light intensity of the pulse can pass through the saturable absorber and be amplified by the gain medium, and the other part of the pulse is lost, so that the width of the pulse is reduced, and stable continuous mode locking is started and maintained.
When the saturable absorber in the passive mode-locking fiber laser of the dual-wavelength fiber Bragg grating under the linear cavity structure does not have the feedback function, an end face feedback element is required to be added into the laser oscillation cavity. The end face reflection element is connected with the saturable absorber in a welding mode to form a linear cavity structure. The end surface reflecting element is a wide spectrum total reflector, a wide spectrum partial reflector or a fiber Bragg grating with matched wavelength.
The pump couplers are divided into two types: when the fiber core is pumped, a wavelength division multiplexer can be adopted; when the cladding is pumped, a tapered beam combiner can be adopted, and the tapered beam combiner can efficiently introduce pump light into the resonant cavity.
The invention combines the dual-wavelength fiber Bragg grating with the saturable absorber, the wavelength of the laser generated by the laser is selected by the dual-wavelength fiber Bragg grating, and the periodic intensity modulation provided by the saturable absorber is used for narrowing the pulse width and locking the phase difference between the laser longitudinal modes, thereby realizing stable and high-efficiency dual-wavelength ultrashort pulse laser output.
The dual-wavelength fiber Bragg grating used in the invention has the characteristics of simple structure, easy integration and high stability, is easy to add into a resonant cavity of a mode-locked fiber laser, and can not change the fiber laser. Under the mechanism, two reflection wavelengths of the dual-wavelength fiber Bragg grating are flexibly and variably selected, and once the refractive index modulation in the fiber Bragg grating is formed, the refractive index modulation cannot be erased, so that stable and efficient dual-wavelength feedback can be provided.
Compared with the prior art, the invention has the following advantages:
the invention adds the dual-wavelength fiber Bragg grating into the passive mode-locking fiber laser innovatively, can provide stable, efficient, flexible and changeable dual-wavelength selection, and can meet the needs of many disciplinary researches requiring dual-wavelength ultrashort pulse laser.
The dual-wavelength fiber Bragg grating used by the invention can be a chirped fiber Bragg grating, and can introduce chromatic dispersion while realizing dual-wavelength feedback, so that an ultrashort pulse forming mechanism in a resonant cavity can be regulated and controlled, and ultrashort pulse laser output with the best overall performance can be realized.
The invention provides wavelength selection characteristic by using the dual-wavelength fiber Bragg grating, ensures full optical fiber of the mode-locked laser, and has simple and compact integral structure, easy manufacture, high stability and extremely high research potential and application value.
In a word, the invention ensures the original advantages of the passive mode-locking fiber laser while realizing stable and efficient dual-wavelength ultrashort pulse laser output, and greatly expands the practical range of the passive mode-locking fiber laser.
Drawings
Fig. 1 is a schematic structural diagram of a dual-wavelength fiber bragg grating according to the present invention.
Fig. 2 is a schematic block diagram of a structure of the passive mode-locked fiber laser based on the dual-wavelength fiber bragg grating, in which the feedback is provided by a saturable absorber under a linear cavity structure and the laser is output by the dual-wavelength fiber bragg grating.
Fig. 3 is a schematic block diagram of a passive mode-locked fiber laser based on a dual-wavelength fiber bragg grating, in which feedback is provided by an end surface feedback device under a linear cavity structure and laser is output by the dual-wavelength fiber bragg grating.
Fig. 4 is a schematic block diagram of a passive mode-locked fiber laser based on a dual-wavelength fiber bragg grating, in which a saturable absorber provides feedback in a linear cavity structure and an output coupler outputs laser light.
Fig. 5 is a schematic block diagram of a passive mode-locked fiber laser based on a dual-wavelength fiber bragg grating, in which feedback is provided by an end feedback device under a linear cavity structure and laser is output by an output coupler.
Fig. 6 is a schematic block diagram of the structure of the passive mode-locked fiber laser based on the dual-wavelength fiber bragg grating when the laser is output by the dual-wavelength fiber bragg grating in the ring cavity structure.
Fig. 7 is a schematic block diagram of the structure of the passive mode-locked fiber laser based on the dual-wavelength fiber bragg grating when the laser is output by the output coupler under the ring cavity structure.
Detailed Description
The present invention is further illustrated with reference to the following examples and the accompanying drawings, but the scope of the present invention should not be limited thereto.
Referring to fig. 1, fig. 1 is a schematic structural diagram of a dual-wavelength fiber bragg grating according to the present invention. It can be seen that there are a set of refractive index modulations with different periods in the upper and lower portions of the core of the same segment of fiber. According to the principle of the fiber Bragg grating, when ultraviolet light is irradiated after being diffracted by a phase mask or is etched by femtosecond laser, so that the refractive index of the fiber core of the fiber is periodically modulated, the laser meeting the Bragg condition can be reflected when passing through the grating, and the specific expression of the Bragg condition is that lambda is 2neffLambda, where lambda is the laser wavelength satisfying the Bragg condition, neffIs the effective index of the fiber core and Λ is the period of index modulation in the core.
The invention adopts a mode of respectively introducing refractive index modulations with different periods into the upper part and the lower part of the same position of the fiber core of the optical fiber to form two modulation periods respectively with lambda in one fiber Bragg grating1And Λ2Thereby realizing a wavelength λ for the sub-fiber Bragg grating1And λ2The feedback of the laser light. At this time, the corresponding relationship between the modulation period and the laser wavelength is λ1＝2neffΛ1And λ2＝2neffΛ2. Under this mechanism to λ1And λ2The choice of (a) is flexible and the refractive index modulation cannot be erased once formed, so that stable and efficient dual wavelength feedback can be provided. When the two wavelengths are both within the gain bandwidth of the laser gain medium and the pump light can provide enough gain, the laser can realize the oscillation and output of the laser with two wavelengths.
Please refer to fig. 2. Fig. 2 is a schematic structural view of a passive mode-locked fiber laser of a dual-wavelength fiber bragg grating according to the first embodiment of the present invention, in which a saturable absorber provides feedback in a linear cavity structure and the dual-wavelength fiber bragg grating outputs laser. It can be seen from the figure that the passive mode-locked fiber laser based on the dual-wavelength fiber bragg grating of the invention comprises a dual-wavelength fiber bragg grating 1, a pumping coupler 3, an active fiber 2, a pumping source 4 and a saturable absorber 6. The dual-wavelength optical fiber Bragg grating 1, the pumping coupler 3, the active optical fiber 2 and the saturable absorber 6 are sequentially connected end to end in a fusion mode to form a linear cavity structure. In this case, the reflectivity of all the sub fiber bragg gratings of the two-wavelength fiber bragg grating 1 is not 100%. The saturable absorber 6 in this case has a feedback function. Pump light emitted by a pump source 4 is injected into a laser cavity through a pump coupler 3, an active optical fiber 2 serves as a laser gain medium to provide gain, the wavelength of the generated laser is selected by the dual-wavelength fiber Bragg grating 1, the mode locking of the selected laser with the proper wavelength is realized through the periodic modulation and the saturation absorption of the saturable absorber 6, and the feedback is obtained from the saturable absorber 6, so that stable and efficient dual-wavelength ultrashort pulse laser is generated and is output from the dual-wavelength fiber Bragg grating 1.
Please refer to fig. 3. Fig. 3 is a schematic structural view of a passive mode-locked fiber laser of a dual-wavelength fiber bragg grating according to a second embodiment of the present invention, in which an end-face feedback device provides feedback in a linear cavity structure and the dual-wavelength fiber bragg grating outputs laser. It can be seen from the figure that the passive mode-locking fiber laser based on the dual-wavelength fiber bragg grating comprises a dual-wavelength fiber bragg grating 1, a pumping coupler 3, an active fiber 2, a pumping source 4, a saturable absorber 6 and an end face feedback device 7. The dual-wavelength optical fiber Bragg grating 1, the pumping coupler 3, the active optical fiber 2, the saturable absorber 6 and the end face reflection element 7 are sequentially connected end to end in a fusion mode to form a linear cavity structure. In this case, the reflectivity of all the sub fiber bragg gratings of the two-wavelength fiber bragg grating 1 is not 100%. The saturable absorber 6 in this case has no feedback function. Pump light emitted by a pump source 4 is injected into a laser cavity through a pump coupler 3, an active optical fiber 2 serves as a laser gain medium to provide gain, the wavelength of the generated laser is selected by the dual-wavelength fiber Bragg grating 1, the selected laser with the appropriate wavelength realizes mode locking through the periodic modulation and the saturation absorption of the saturable absorber 6, and the feedback is obtained from the end face feedback device 7, so that stable and efficient dual-wavelength ultrashort pulse laser is generated and is output from the dual-wavelength fiber Bragg grating 1.
Please refer to fig. 4. Fig. 4 is a schematic structural diagram of a passive mode-locked fiber laser of a dual-wavelength fiber bragg grating according to a third embodiment of the present invention, in which a saturable absorber provides feedback in a linear cavity structure and a laser is output by an output coupler. It can be seen from the figure that the passive mode-locking fiber laser based on the dual-wavelength fiber bragg grating comprises a dual-wavelength fiber bragg grating 1, a pumping coupler 3, an active fiber 2, a pumping source 4, an output coupler 5 and a saturable absorber 6. The dual-wavelength optical fiber Bragg grating 1, the pumping coupler 3, the active optical fiber 2, the output coupler 5 and the saturable absorber 6 are sequentially connected end to end in a fusion mode to form a linear cavity structure. At least one reflectivity of the sub fiber bragg grating of the dual wavelength fiber bragg grating 1 is 100%. The saturable absorber 6 in this case has a feedback function. Pump light emitted by a pump source 4 is injected into a laser cavity through a pump coupler 3, an active optical fiber 2 serves as a laser gain medium to provide gain, the wavelength of the generated laser is selected by the dual-wavelength fiber Bragg grating 1, the mode locking of the selected laser with the proper wavelength is realized through the periodic modulation and the saturation absorption of the saturable absorber 6, and the feedback is obtained from the saturable absorber 6, so that stable and efficient dual-wavelength ultrashort pulse laser is generated and is output from the dual-wavelength fiber Bragg grating 1.
Please refer to fig. 5. Fig. 5 is a schematic structural diagram of a passive mode-locked fiber laser based on a dual-wavelength fiber bragg grating according to a linear cavity structure, which is a fourth embodiment of the present invention. It can be seen from the figure that the passive mode-locked fiber laser based on the dual-wavelength fiber bragg grating of the invention comprises a dual-wavelength fiber bragg grating 1, a pumping coupler 3, an active fiber 2, a pumping source 4, an output coupler 5, a saturable absorber 6 and an end face reflection element 7. The dual-wavelength optical fiber Bragg grating 1, the pumping coupler 3, the active optical fiber 2, the output coupler 5, the saturable absorber 6 and the end face reflection element 7 are sequentially connected end to end in a fusion mode to form a linear cavity structure. At least one reflectivity of the sub fiber bragg grating of the dual wavelength fiber bragg grating 1 is 100%. The saturable absorber 6 in this case has no feedback function. Pump light emitted by a pump source 4 is injected into a laser cavity through a pump coupler 3, an active optical fiber 2 serves as a laser gain medium to provide gain, the wavelength of the generated laser is selected by a dual-wavelength fiber Bragg grating 1, the selected laser with the appropriate wavelength realizes mode locking through the periodic modulation and the saturation absorption of a saturable absorber 6, and the feedback is obtained from an end face feedback device 7, so that stable and efficient dual-wavelength ultrashort pulse laser is generated and is output from an output coupler 5.
Please refer to fig. 6. Fig. 6 is a schematic structural diagram of a passive mode-locked fiber laser based on a dual-wavelength fiber bragg grating according to the present invention when a laser is output from the dual-wavelength fiber bragg grating in a ring cavity structure, which is a fifth embodiment of the present invention. As can be seen from the figure, the passive mode-locking fiber laser based on the dual-wavelength fiber Bragg grating comprises a dual-wavelength fiber Bragg grating 1, an active fiber 2, a pump coupler 3, a pump source 4, a saturable absorber 6 and a circulator 8. The pump coupler 3, the active optical fiber 2, the saturable absorber 6 and the circulator 8 are sequentially welded end to end, and a port d of the pump coupler 3 is welded with a port c of the circulator 8 to form a ring cavity structure. The circulator 8 is characterized in that light input from the port a is output from the port b, and light input from the port b is output from the port c. The dual wavelength fiber bragg grating 1 is fusion-connected with the port b of the circulator 8 so as to be added into the ring cavity. At the moment, the circulator 8 not only plays a role of introducing the dual-wavelength fiber Bragg grating 1 into the annular cavity, but also ensures that laser in the cavity can only operate in a single direction. The reflectivity of the sub fiber bragg grating of the two-wavelength fiber bragg grating 1 at this time is not 100% at all. Pump light emitted by a pump source 7 is injected into a laser cavity through a pump coupler 5, an active optical fiber 2 serves as a laser gain medium to provide gain, the wavelength of the generated laser is selected by the dual-wavelength fiber Bragg grating 1, and mode locking is realized by the selected laser with the appropriate wavelength through the periodic modulation and the saturated absorption action of the saturable absorber 6, so that stable and efficient dual-wavelength ultrashort pulse laser is generated and is output from the dual-wavelength fiber Bragg grating 1.
Please refer to fig. 7. Fig. 7 is a schematic structural diagram of a passive mode-locked fiber laser based on a dual-wavelength fiber bragg grating according to the present invention when laser is output from an output coupler in a ring cavity structure, which is a sixth embodiment of the present invention. It can be seen from the figure that the passive mode-locked fiber laser based on the dual-wavelength fiber bragg grating comprises a dual-wavelength fiber bragg grating 1, an active fiber 2, a pump coupler 3, a pump source 4, an output coupler 5, a saturable absorber 6 and a circulator 8. The pump coupler 3, the active optical fiber 2, the output coupler 5, the saturable absorber 6 and the circulator 8 are sequentially connected end to end in a fusion mode, and a port d of the pump coupler 3 is connected with a port c of the circulator 8 in a fusion mode to form a ring cavity structure. The circulator 8 is characterized in that light input from the port a is output from the port b, and light input from the port b is output from the port c. The dual wavelength fiber bragg grating 1 is fusion-connected with the port b of the circulator 8 so as to be added into the ring cavity. At the moment, the circulator 8 not only plays a role of introducing the dual-wavelength fiber Bragg grating 1 into the annular cavity, but also ensures that laser in the cavity can only operate in a single direction. At least one reflectivity of the sub fiber bragg grating of the dual wavelength fiber bragg grating 1 is 100%. Pump light emitted by a pump source 7 is injected into a laser cavity through a pump coupler 5, an active optical fiber 2 serves as a laser gain medium to provide gain, the wavelength of the generated laser is selected by a dual-wavelength fiber Bragg grating 1, and mode locking is realized by the selected laser with the appropriate wavelength through the periodic modulation and the saturated absorption action of a saturable absorber 6, so that stable and efficient dual-wavelength ultrashort pulse laser is generated and is output from an output coupler 5.

Claims (8)

1. A passive mode-locking fiber laser based on dual-wavelength fiber Bragg grating is characterized in that: the dual-wavelength optical fiber Bragg grating optical fiber laser device comprises a dual-wavelength optical fiber Bragg grating (1), an active optical fiber (2), a pumping coupler (3), a pumping source (4) and a saturable absorber (6), wherein the dual-wavelength optical fiber Bragg grating (1) is sequentially connected with the pumping coupler (3), the active optical fiber (2) and the saturable absorber (6) in a fusion mode to form a linear cavity structure, and a 3 rd port of the pumping coupler (5) is connected with the pumping source (4).
2. A passive mode-locking fiber laser based on dual-wavelength fiber Bragg grating is characterized in that: comprises a dual-wavelength fiber Bragg grating (1), an active fiber (2), a pumping coupler (3), a pumping source (4), a saturable absorber (6) and a circulator (8), the pump coupler (3), the active optical fiber (2), the saturable absorber (6) and the circulator (8) are sequentially welded end to end, the port d of the pump coupler (3) is connected with the port c of the circulator (8) in a welding way to form a ring cavity structure, the circulator (8) is characterized in that the light input by the port a can only be output from the port b, the light input by the port b can only be output from the port c, the dual-wavelength optical fiber Bragg grating (1) is connected with the port b of the circulator (8) in a welding way, thereby adding into the ring cavity, and the port e of the pump coupler (5) is connected with the output port of the pump source (4).
3. The passive mode-locked fiber laser based on dual-wavelength fiber bragg grating as claimed in claims 1 and 2, wherein: the dual-wavelength fiber Bragg grating (1) is characterized in that refractive index modulation with different periods is respectively introduced into the upper position and the lower position of the fiber core of the same section of optical fiber, two sub-fiber Bragg gratings with different reflection wavelengths are obtained in the same section of optical fiber, the two wavelengths can be reflected, and when the two wavelengths are both positioned in the gain bandwidth of the gain optical fiber, the high-efficiency and stable dual-wavelength ultrashort pulse laser output can be realized by matching with the saturable absorber (6).
4. The passive mode-locked fiber laser based on dual-wavelength fiber bragg grating as claimed in claims 1 and 2, wherein: the two sub-fiber Bragg gratings of the dual-wavelength fiber Bragg grating (1) are respectively common fiber Bragg gratings with the same refractive index change period or chirped fiber Bragg gratings with the refractive index change period changing along the axial direction.
5. The passive mode-locked fiber laser based on dual-wavelength fiber bragg grating as claimed in claims 1 and 2, wherein: the reflectivity of two sub fiber Bragg gratings of the dual-wavelength fiber Bragg grating (1) can be respectively in the range of 1-100%, when the reflectivity of one of the sub fiber Bragg gratings in the dual-wavelength fiber Bragg grating (1) is 100%, an output coupler (5) needs to be inserted into the resonant cavity of the laser, and the output coupler (5) can be a fused biconical taper beam splitter or a coating film beam splitter so as to output laser to the outside of the resonant cavity according to a certain proportion.
6. The passive mode-locked fiber laser based on dual-wavelength fiber bragg grating as claimed in claims 1 and 2, wherein: the active optical fiber (2) is gain optical fiber doped with ytterbium, erbium, thulium or bismuth, or nonlinear optical fiber capable of generating stimulated Raman scattering, stimulated Brillouin scattering and optical parameter process.
7. The passive mode-locked fiber laser based on dual-wavelength fiber bragg grating as claimed in claims 1 and 2, wherein: the saturable absorber (6) is a true saturable absorber with feedback function and based on material absorption characteristics, such as a semiconductor saturable absorber mirror, a true saturable absorber without feedback function and based on material absorption characteristics, such as carbon nano tubes and graphene, an equivalent saturable absorber with feedback function and based on nonlinear effect in optical fiber, such as a nonlinear optical ring mirror and a nonlinear amplification ring mirror, and an equivalent saturable absorber without feedback function and based on nonlinear effect in optical fiber, such as nonlinear polarization rotation.
8. The passive mode-locked fiber laser based on dual wavelength fiber bragg grating as claimed in claims 1 and 7, wherein: when the saturable absorber (6) does not have a feedback function, an end face reflector (7) is required to be added in the cavity, the end face reflector and the saturable absorber are fused to form a linear cavity structure, and the end face reflector (7) is a wide-spectrum total reflector, a wide-spectrum partial reflector or a fiber Bragg grating with matched wavelength.
CN201911355766.0A 2019-12-25 2019-12-25 Mode-locked fiber laser based on dual-wavelength fiber Bragg grating Withdrawn CN110994342A (en)

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US11233372B2 (en) * 2019-06-25 2022-01-25 Lumentum Operations Llc Femtosecond pulse stretching fiber oscillator
CN116720232A (en) * 2023-06-13 2023-09-08 上海频准激光科技有限公司 Method for selecting a fiber laser assembly
CN117033456A (en) * 2023-06-13 2023-11-10 上海频准激光科技有限公司 Recommendation system for fiber laser

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US11233372B2 (en) * 2019-06-25 2022-01-25 Lumentum Operations Llc Femtosecond pulse stretching fiber oscillator
US11817672B2 (en) 2019-06-25 2023-11-14 Lumentum Operations Llc Femtosecond pulse stretching fiber oscillator
CN116720232A (en) * 2023-06-13 2023-09-08 上海频准激光科技有限公司 Method for selecting a fiber laser assembly
CN117033456A (en) * 2023-06-13 2023-11-10 上海频准激光科技有限公司 Recommendation system for fiber laser
CN116720232B (en) * 2023-06-13 2023-12-15 上海频准激光科技有限公司 Method for selecting a fiber laser assembly
CN117033456B (en) * 2023-06-13 2024-03-22 上海频准激光科技有限公司 Recommendation system for fiber laser

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