CN109755850B - Intermediate infrared Raman ultrafast fiber laser oscillator based on micro-cavity - Google Patents
Intermediate infrared Raman ultrafast fiber laser oscillator based on micro-cavity Download PDFInfo
- Publication number
- CN109755850B CN109755850B CN201910174040.0A CN201910174040A CN109755850B CN 109755850 B CN109755850 B CN 109755850B CN 201910174040 A CN201910174040 A CN 201910174040A CN 109755850 B CN109755850 B CN 109755850B
- Authority
- CN
- China
- Prior art keywords
- microcavity
- fiber
- raman
- optical fiber
- ultrafast
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Active
Links
- 239000000835 fiber Substances 0.000 title claims abstract description 96
- 238000001069 Raman spectroscopy Methods 0.000 title claims abstract description 85
- 239000013307 optical fiber Substances 0.000 claims abstract description 71
- 230000003287 optical effect Effects 0.000 claims abstract description 30
- 230000010287 polarization Effects 0.000 claims abstract description 25
- 238000005086 pumping Methods 0.000 claims abstract description 24
- 239000006096 absorbing agent Substances 0.000 claims abstract description 22
- 239000006185 dispersion Substances 0.000 claims abstract description 21
- 239000000463 material Substances 0.000 claims abstract description 9
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 18
- 230000008878 coupling Effects 0.000 claims description 17
- 238000010168 coupling process Methods 0.000 claims description 17
- 238000005859 coupling reaction Methods 0.000 claims description 17
- 239000004005 microsphere Substances 0.000 claims description 14
- 239000004065 semiconductor Substances 0.000 claims description 14
- 229910052761 rare earth metal Inorganic materials 0.000 claims description 12
- 238000005520 cutting process Methods 0.000 claims description 10
- 239000010453 quartz Substances 0.000 claims description 10
- KRHYYFGTRYWZRS-UHFFFAOYSA-M Fluoride anion Chemical compound [F-] KRHYYFGTRYWZRS-UHFFFAOYSA-M 0.000 claims description 8
- -1 rare earth ion Chemical class 0.000 claims description 7
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 6
- WUKWITHWXAAZEY-UHFFFAOYSA-L calcium difluoride Chemical compound [F-].[F-].[Ca+2] WUKWITHWXAAZEY-UHFFFAOYSA-L 0.000 claims description 5
- 229910001634 calcium fluoride Inorganic materials 0.000 claims description 5
- 150000002910 rare earth metals Chemical class 0.000 claims description 5
- 229910021389 graphene Inorganic materials 0.000 claims description 4
- 239000000377 silicon dioxide Substances 0.000 claims description 4
- 229910052710 silicon Inorganic materials 0.000 claims description 3
- 239000010703 silicon Substances 0.000 claims description 3
- PFNQVRZLDWYSCW-UHFFFAOYSA-N (fluoren-9-ylideneamino) n-naphthalen-1-ylcarbamate Chemical compound C12=CC=CC=C2C2=CC=CC=C2C1=NOC(=O)NC1=CC=CC2=CC=CC=C12 PFNQVRZLDWYSCW-UHFFFAOYSA-N 0.000 claims description 2
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims description 2
- 239000002041 carbon nanotube Substances 0.000 claims description 2
- 229910021393 carbon nanotube Inorganic materials 0.000 claims description 2
- 229910052732 germanium Inorganic materials 0.000 claims description 2
- GNPVGFCGXDBREM-UHFFFAOYSA-N germanium atom Chemical compound [Ge] GNPVGFCGXDBREM-UHFFFAOYSA-N 0.000 claims description 2
- 230000000694 effects Effects 0.000 abstract description 10
- 238000000034 method Methods 0.000 abstract description 9
- 238000010521 absorption reaction Methods 0.000 abstract description 8
- 238000005516 engineering process Methods 0.000 abstract description 4
- 239000013078 crystal Substances 0.000 abstract description 3
- 230000001427 coherent effect Effects 0.000 abstract 1
- 238000004891 communication Methods 0.000 abstract 1
- 230000007123 defense Effects 0.000 abstract 1
- 238000010586 diagram Methods 0.000 description 9
- 238000001237 Raman spectrum Methods 0.000 description 4
- 230000004907 flux Effects 0.000 description 4
- 230000008859 change Effects 0.000 description 3
- 238000002360 preparation method Methods 0.000 description 3
- 238000003466 welding Methods 0.000 description 3
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 2
- 229910002092 carbon dioxide Inorganic materials 0.000 description 2
- 239000001569 carbon dioxide Substances 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 2
- 238000001816 cooling Methods 0.000 description 2
- 230000003247 decreasing effect Effects 0.000 description 2
- 238000002474 experimental method Methods 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 230000008569 process Effects 0.000 description 2
- 238000001228 spectrum Methods 0.000 description 2
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000011247 coating layer Substances 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 230000004927 fusion Effects 0.000 description 1
- 238000007526 fusion splicing Methods 0.000 description 1
- 238000000227 grinding Methods 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 238000003384 imaging method Methods 0.000 description 1
- 230000003993 interaction Effects 0.000 description 1
- 238000002955 isolation Methods 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- 238000001000 micrograph Methods 0.000 description 1
- 238000004476 mid-IR spectroscopy Methods 0.000 description 1
- 230000010355 oscillation Effects 0.000 description 1
- 238000005498 polishing Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
Images
Landscapes
- Lasers (AREA)
Abstract
The invention discloses a micro-cavity-based intermediate infrared Raman ultrafast fiber laser oscillator, and belongs to the field of laser technology and nonlinear optics. The laser oscillator adopts a linear cavity structure and mainly comprises a mode locking element saturable absorber, a pumping source, an optical fiber beam combiner, a gain optical fiber for generating 2-5 micron laser, a dispersion compensation element, a polarization controller and a high-Q-value microcavity, wherein the high-Q-value microcavity is a whispering gallery mode optical microcavity, and the Q value of a quality factor of the microcavity is not lower than 106. The method utilizes the saturable absorption effect of the saturable absorption crystal and the Raman scattering effect of the high-Q-value microcavity to replace the traditional method of increasing nonlinearity in the cavity by using the optical fiber with the kilometer-level length, can generate coherent mode-locked pulse laser, and directly realizes long-wave Raman frequency shift by oscillating in the cavity to obtain 2-5 micron ultrafast Raman laser with high repetition rate and high power; the invention can be applied to the fields of basic research, national defense, communication sensing, biological medical treatment, material processing and the like.
Description
Technical Field
The invention belongs to the field of laser technology and nonlinear optics, and particularly relates to a micro-cavity-based mid-infrared Raman ultrafast fiber laser oscillator.
Background
Due to waveDue to the long and flexible characteristics, the raman fiber laser has been paid attention to by researchers. At present, the wavelength range of the Raman laser covers visible light to middle infrared bands, and the maximum output power in the near infrared band can exceed kilowatt. The existing development of high power raman fiber laser technology has the following characteristics: 1, amplifying power by a plurality of ultrafast seed sources to realize a high-power Raman fiber laser, wherein the method needs a plurality of pumping sources and isolators, so that the cavity structure is complex, the cost is high and the reliability is low; 2 though in the near infrared band, Yb3+Ion-doped fiber laser and Er3+The ion-doped fiber laser can form an oscillator through a kilometer-magnitude long fiber, so that Raman ultrafast laser output is directly realized in a cavity; however, the long fiber of kilometer magnitude causes the threshold value of the Raman laser to be very high, and the obtained pulse repetition frequency is in tens of kilohertz magnitude and is two magnitudes lower than that of the common mode-locked fiber laser. This is why the mid-infrared band raman ultrafast fiber laser oscillator is lacking.
At present, a 2-5 micron waveband Raman fiber laser oscillator is not reported, and two main reasons are that the nonlinear intensity of the interaction between light and a substance is inversely proportional to the wavelength of the light (the photon energy is directly proportional), so that the Raman threshold is increased along with the increase of the wavelength of the light; secondly, as the wavelength is close to 2 microns, the intrinsic loss of the quartz fiber to laser in the waveband is increased, and the Raman threshold is more difficult to achieve, so that the 2-micron-waveband Raman ultrafast laser based on the long fiber has high threshold and a complex structure. Because the repetition frequency of the pulses can be controlled by
And (6) calculating. Where f is the pulse repetition frequency, L represents the path of light once again within the cavity, and c represents the speed of light. From the above formula, it is known that the pulse repetition frequency is inversely proportional to the cavity length, and therefore, in order to obtain a high repetition frequency, the cavity length should be as short as possible.
Disclosure of Invention
In order to solve the problem of high threshold value and low repetition frequency caused by realizing output of the intermediate infrared Raman ultrafast laser through a long cavity, the invention provides an intermediate infrared Raman ultrafast fiber laser oscillator based on a microcavity.
In order to achieve the purpose, the technical scheme adopted by the invention is as follows: a middle infrared Raman ultrafast fiber laser oscillator based on a microcavity adopts a linear cavity structure and mainly comprises a mode locking element saturable absorber, a lens I, a lens II, a pump source, a fiber combiner, a gain fiber, a dispersion compensation element, a polarization controller and a microcavity with a high Q value, wherein the microcavity with the high Q value is a whispering gallery mode optical microcavity, and the Q value of a quality factor of the microcavity is not lower than 106；
Cutting an oblique angle with an angle alpha of 8-20 degrees at one side of a signal input end of an optical fiber combiner, wherein emergent light of the oblique angle vertically irradiates to the center of a lens, namely, one end of the oblique angle with an angle is focused on a saturable absorber of a mode locking element through a lens with a proper focal length, a flat angle end of the oblique angle is connected with the signal input end of the optical fiber combiner to form resonance, a pump source is connected with a pump end of the optical fiber combiner, one end of a gain optical fiber is connected with a signal output end of the optical fiber combiner, the other end of the gain optical fiber is connected with one end of a dispersion compensation element, the other end of the dispersion compensation element is connected with one end of a polarization controller, a microcavity with a high Q value is connected behind the polarization controller, or a microcavity with a high Q value is connected between the optical fiber combiner.
Preferably, the high-Q microcavity is one of a microsphere type, a micro-cylinder type, a micro-disk type, a micro-bubble type, a micro-tube type or a micro-ring type.
Preferably, the material of the microcavity with the high Q value is one of quartz with low loss at a wave band of 2 microns or silicon, germanium, calcium fluoride and zinc selenide with low loss at a wave band of 3 microns.
Preferably, the coupling mode of the microcavity with the high Q value is one of tapered fiber coupling or prism-to-free space coupling.
Preferably, the mode locking element saturable absorber is one of a semiconductor saturable absorber mirror, a graphene saturable absorber mirror, a carbon nanotube saturable absorber mirror or a graphene oxide saturable absorber mirror, the working range of the mode locking element saturable absorber mirror covers a 2-3 micron wave band, and the value range of the modulation depth delta R is more than or equal to 8% and less than or equal to 30%.
Preferably, the pumping source is a semiconductor laser pumping source, the central wavelength lambda is 793nm or 976nm, and the corresponding rare earth ion doped gain fiber is excited to generate laser with a wave band of 2-5 microns.
Preferably, the gain fiber is rare earth single-doped Tm3+Quartz fiber or rare earth ion Tm3+、Ho3+Co-doped silica fiber for generating 1.6-2.2 μm laser or Er3+The doped fluoride optical fiber is used for generating laser of about 3 microns, and then the laser is subjected to Raman frequency shift to obtain first-order Stokes laser and high-order Stokes laser, so that the intermediate infrared ultrafast laser with the wavelength of 2-5 microns can be generated.
Preferably, the dispersion compensation element is a dispersion compensation fiber or a chirped fiber grating.
Further, the micro-cavity-based mid-infrared Raman ultrafast fiber laser oscillator further comprises a band-pass filter, and the band-pass filter is connected outside the resonant cavity.
Compared with the prior art, the invention has the following beneficial effects:
1. good wavelength expansion characteristic, simple and compact structure and easy wavelength switching. By exciting rare earth single doping Tm3+Quartz fiber or rare earth ion Tm3+、Ho3+The co-doped quartz fiber provides laser with the gain of about 2 microns, the central wavelength and the gain in the cavity are changed by increasing or decreasing the length of the gain fiber, the Raman frequency shift is realized in the cavity through the Raman scattering effect of the microcavity element, the cascade Raman is realized by increasing the pumping power, and the laser is moved to the long wave direction through the Raman frequency shift, so that the Raman laser with the wavelength of 2-3 microns can be output. Likewise, Er by excitation3+The doped fluoride fiber provides laser with the gain of about 3 microns, and can generate Raman laser with the wavelength of 3-5 microns through Raman frequency shift.
2. The femtosecond laser with high repetition frequency (nearly hundred megahertz) and high power (watt level) can be realized. The present invention uses microcavities as the primary element providing the raman effect. The microcavity has an extremely high Q value and an extremely low optical nonlinear threshold, the difficulty in realizing the intermediate infrared Raman laser is greatly reduced, long-wave Raman frequency shift can be directly realized through intracavity oscillation, and high-repetition-rate and watt-level high-power 2-5 micron ultrafast Raman laser with a repetition rate of tens of megahertz is obtained. And the microcavity can be made of common materials such as quartz or silicon, so that the cost is low, the process is simple, and the practical application requirements are met.
3. And a simple linear structure is adopted, so that the damage threshold is high, and the maintainability is strong. The invention adopts the free space linear resonance structure formed by the rare earth ion doped fiber and the bevel angle, and the linear cavity structure does not need a complex isolation device, thereby reducing the cost. The resonant structure greatly improves the energy required by the Raman laser in the cavity, thereby improving the output power and efficiency of the mid-infrared Raman laser oscillator. Aiming at the damage characteristic of the saturable absorption mirror, the adopted free space structure enables the position of the saturable absorption mirror to be adjustable, so that the mid-infrared Raman laser oscillator has good maintainability and long service life.
4. The invention adopts the passive mode locking technology to generate the ultrashort pulse laser, does not need an external additional modulation source and has simple structure. The invention adopts the saturable absorber as a mode locking device, and the mode locking performance is more stable.
Drawings
FIG. 1 is a basic schematic diagram of a microcavity-based intermediate infrared Raman ultrafast fiber laser oscillator according to embodiment 1 of the present invention;
FIG. 2 is a drawing of a tapered optical fiber preparation apparatus;
FIG. 3 is a diagram of a microspherical whispering gallery mode optical microcavity fabrication apparatus;
FIG. 4 is an imaging view of the prepared microsphere-type whispering gallery mode optical microcavity microscope with an optical fiber handle;
FIG. 5 is a microscope image of coupling of a microspheric whispering gallery mode optical microcavity and a tapered fiber;
FIG. 6 is a graph of a sequence of mode-locked pulses expected to be obtained in example 1 of the present invention;
FIG. 7 is a Raman spectrum expected from example 1 of the present invention;
FIG. 8 is a basic schematic diagram of a microcavity-based mid-IR Raman ultrafast fiber laser oscillator according to embodiment 2 of the present invention;
FIG. 9 is an image of the prepared microdisk whispering gallery mode optical microcavity microscope: (a) overlook, (b) main view;
FIG. 10 is a graph of a sequence of mode-locked pulses expected from example 2 of the present invention;
FIG. 11 is a Raman spectrum expected from example 2 of the present invention.
In the figure, 1-mode locking element saturable absorber, 2-lens I, 3-lens II, 4-bevel angle, 5-pumping source, 6-optical fiber beam combiner, 7-gain optical fiber, 801-dispersion compensation optical fiber, 802-chirped fiber grating, 9-polarization controller, 101-microspheric echo wall mode optical microcavity, 102-microdisc echo wall mode optical microcavity, 11-band-pass filter, 12-single mode optical fiber, 13-stepping motor, 14-computer, 15-motor drive, 16-camera, 17-three-dimensional moving platform, 18-carbon dioxide laser, 19-focusing lens, 20-optical fiber handle and 21-tapered optical fiber.
Detailed Description
The invention is described in further detail below with reference to the figures and specific examples.
Example 1 Generation of 2-3 micron Raman mode-locked laser based on 2 micron wavelength pumping
A microcavity-based mid-infrared raman ultrafast fiber laser oscillator structure is shown in fig. 1, and includes:
the mode locking element saturable absorber 1 selects a broadband semiconductor saturable absorber mirror (SESAM) with a wave band of 2 mu m, the modulation depth range of the SESAM is more than or equal to 8% and less than or equal to 30%, and the pulse energy in the cavity is controlled by increasing the pumping power, so that when the pulse energy flux reaches 3-5 times of the saturation flux, the three-dimensional space position of the SESAM is properly adjusted to achieve mode locking;
the focal length of the lens I2 is 50 mm;
a lens II 3 with the focal length of 100 mm;
and 4, cutting an oblique angle with an angle of 8-20 degrees by using an optical fiber oblique angle cutting knife to prevent laser feedback and avoid the mode locking state from being damaged by the F-P effect.
The pumping source 5 is a semiconductor laser pumping source with the central wavelength of 793nm, the maximum output power is 30W, and the corresponding gain optical fiber can be excited to generate laser with a 2-micron wave band;
the optical fiber combiner 6 is a (2+1) × 1 quartz optical fiber combiner, and the pumping end of the combiner is connected with the LD tail fiber in a fusion mode;
a gain fiber 7, rare earth single doped Tm is selected3+Quartz fiber or rare earth ion Tm3+、Ho3+A co-doped silica optical fiber;
the dispersion compensation element selects UHNA4 dispersion compensation fiber 801 to adjust the relative balance of nonlinearity and dispersion in the resonant cavity, thereby realizing the tunability of pulse width;
the polarization controller 9 is a manual polarization controller or an electric polarization controller, and in the embodiment, the manual polarization controller is adopted, the optical fiber is pulled by rotating the polarization control sheet so as to change the non-polarization state in the cavity, so that the cost is low, the operation is flexible, and the polarization controller is convenient to fix after being adjusted to a proper polarization state, so that the stability of the system is enhanced;
a micro-spherical whispering gallery mode optical microcavity 101 is selected as the high-Q-value microcavity;
cutting an oblique angle 4 with an angle of 8-20 degrees at the signal input end of the (2+1) multiplied by 1 optical fiber beam combiner 6 to prevent laser feedback and avoid the mode locking state from being damaged by the F-P effect; one end with an angle of the bevel angle 4 sequentially passes through the lens II 3 with the focal length of 100mm and the lens I2 with the focal length of 50mm and then is focused on the semiconductor saturable absorption mirror 1, so that the energy of light spots incident on the semiconductor saturable absorption mirror 1 is larger, and the mode locking threshold value is favorably reached; the flat-angle end of the bevel angle 4 is connected with the signal input end of the (2+1) x 1 optical fiber combiner 6 to form resonance, the pumping source 5 of the semiconductor laser is connected with the pumping end of the (2+1) x 1 optical fiber combiner 6, one end of the gain optical fiber 7 is connected with the signal output end of the (2+1) x 1 optical fiber combiner 6, the other end of the gain optical fiber 7 is sequentially connected with the dispersion compensation optical fiber 801, the polarization controller 9 and the microspheric whispering gallery mode optical microcavity 101, and the output end of the microspheric whispering gallery mode optical microcavity 101 adopts a mode of directly outputting from the end face of the optical fiber, so that the mid-infrared Raman ultrafast optical fiber laser oscillator based on the microcavity outputs high-power Raman laser. A band-pass filter 11 with a wave band of 2 microns is connected outside the resonant cavity to obtain the output of the Raman laser with a specific wavelength. The optical fibers between all the optical elements are connected by means of ordinary fusion splicing.
The preparation method of the microspheric whispering gallery mode optical microcavity is a high-temperature melting cooling method, and comprises the following specific steps:
firstly, preparing a tapered optical fiber by adopting a flame tapering method: a section of single mode fiber 12 is removed of a coating layer and cleaned by alcohol, then the single mode fiber is fixed on a pair of stepping motors 13 by a clamp, the stepping motors 13 are controlled by a computer 14 to drive a motor 15, a flame nozzle is fixed under the single mode fiber 12, the flame size is adjusted when an experiment is started, the fiber is positioned in an outer flame, the stepping motors 13 are set to move away at the same speed to drive the fiber to stretch towards two ends, a conical structure is formed gradually, and a camera 16 feeds back image information to the computer 14. In the experiment, the whole process is controlled by controlling parameters such as the step length, the moving speed and the like of the stepping motor 13, and the tapered optical fibers with various structural parameters are prepared; the drawing of the tapered optical fiber preparation device is shown in FIG. 2.
The method comprises the steps of preparing a conical optical fiber by using a flame tapering method, cutting the conical optical fiber, fixing the obtained single-cone optical fiber on a three-dimensional moving platform 17, focusing laser emitted by a carbon dioxide laser 18 to one end to be cut through a focusing lens 19 for heating, automatically curling the optical fiber upwards under the action of surface tension to form a sphere, cooling to obtain a microspheric microcavity 101 with an optical fiber handle 20, and feeding image information back to a computer 14 by a camera 16. The spherical micro-cavity prepared by the method has good uniformity and smooth surface, is provided with a section of optical fiber handle 20, and is easy to operate. FIG. 3 is a diagram of a microspheric whispering gallery mode optical microcavity fabrication apparatus. FIG. 4 is an image of an experimentally prepared microspheric whispering gallery mode optical microcavity microscope with an optical fiber handle, with a diameter of 50 μm and a measured Q-value of 106。
The microsphere-type microcavity coupling mode in embodiment 1 is to couple by using a tapered fiber, draw the fiber core diameter of the tapered fiber 21 to 2 μm to ensure that enough light is coupled from the tapered fiber 21 to the microsphere-type whispering gallery mode optical microcavity 101, and control the coupling ratio by controlling the distance between the microsphere-type whispering gallery mode optical microcavity 101 and the tapered fiber, which is high in coupling efficiency and simple in operation, and a microscopic image of coupling between the microsphere and the tapered fiber is shown in fig. 5.
The microcavity-based intermediate infrared Raman ultrafast fiber laser oscillator can realize the tuning of the central wavelength by increasing and decreasing the length of the gain fiber and adjusting the rare earth ion doping concentration of the gain fiber, and the adjustment range is 1.8-2 microns; raman frequency shift can be realized in the cavity through the Raman scattering effect of the microcavity element; by increasing the coupling efficiency of the pumping power and the microsphere cavity, the control of Raman intensity can be realized, so that the conversion from first-order Raman to high-order Raman is realized, and 2-3 micron Raman laser can be obtained. A band-pass filter with a wave band of 2 microns is additionally arranged outside the cavity, and the needed Raman laser with a specific wave band can be obtained.
The microcavity-based intermediate infrared Raman ultrafast fiber laser oscillator can observe a mode-locked pulse diagram through an oscilloscope (with the detection speed of 1GHz), the mode-locked pulse diagram is shown in figure 6, the pulse mode is stable, and the repetition frequency is 16 MHz. Raman spectra can be observed by a spectrometer (measuring wavelength band from 1600nm to 3400 nm). The Raman frequency shifts generated by different optical fiber materials are different, but the Raman frequency shift value of the same material is fixed and constant, is irrelevant to the wavelength change of incident light, and can be calculated according to a formula
Calculating the ith Stokes laser output wavelength lambda of the Raman fiber laseriWherein λ isi-1As the wavelength of incident light, Δ s is the amount of Raman frequency shift of the optical fiber used, and the Raman frequency shift of the silica fiber is 13.2THz (440 cm)-1). In example 1, raman laser light is expected to be observed in the 2150nm band on the spectrometer, and a spectrum diagram expected to be obtained is shown in fig. 7. Meanwhile, the pulse width and the substructure of the obtained ultrafast pulse are further measured using an autocorrelator.
Example 2 generating 3-5 micron Raman laser based on 3 micron wavelength pump
A microcavity-based mid-infrared raman ultrafast fiber laser oscillator structure is shown in fig. 8, and includes:
the mode locking element saturable absorber 1 is characterized in that a broadband semiconductor saturable absorber mirror (SESAM) with a wave band of 3 micrometers (2000 nm-3400nm) is selected, the modulation depth range of the SESAM is more than or equal to 8% and less than or equal to 30%, and pulse energy in a cavity is controlled by increasing pumping power, so that when pulse energy flux reaches 3-5 times of saturation flux, the three-dimensional space position of the SESAM is properly adjusted to achieve mode locking;
the focal length of the lens I2 is 50 mm;
a lens II 3 with the focal length of 100 mm;
and 4, cutting an oblique angle with an angle of 8-20 degrees by using an optical fiber oblique angle cutting knife to prevent laser feedback and avoid the mode locking state from being damaged by the F-P effect.
The pumping source 5 is a semiconductor laser pumping source with the central wavelength of 976nm, the maximum output power is 30W, and the corresponding gain optical fiber can be excited to generate laser with a wave band of 3 microns;
the optical fiber combiner 6 is a (2+1) x 1 fluoride optical fiber combiner, wherein a pumping end of the combiner is connected with the LD tail fiber in a mechanical splicing mode;
the gain optical fiber 7 is made of rare earth doped Er3+Fluoride optical fiber, Er3+The doping molar concentration can range from 7% to 20%, and the molar doping concentration of 7% is selected in the embodiment;
the dispersion compensation element selects the chirped fiber grating 802 carved by the fluoride fiber to compensate the dispersion in the cavity, so as to adjust the relative balance of nonlinearity and dispersion in the resonant cavity and realize the tunability of the pulse width;
the polarization controller 9 is a manual polarization controller or an electric polarization controller, and in the embodiment, the manual polarization controller is adopted, the optical fiber is pulled by rotating the polarization control sheet so as to change the non-polarization state in the cavity, so that the cost is low, the operation is flexible, and the polarization controller is convenient to fix after being adjusted to a proper polarization state, so that the stability of the system is enhanced;
the microcavity with high Q value is a micro-disk whispering gallery mode optical microcavity prepared from calcium fluoride crystal.
Cutting an oblique angle 4 with an angle of 8-20 degrees at the signal input end of the (2+1) multiplied by 1 optical fiber beam combiner 6 to prevent laser feedback and avoid the mode locking state from being damaged by the F-P effect; one end with an angle of the bevel angle 4 sequentially passes through the lens II 3 with the focal length of 100mm and the lens I2 with the focal length of 50mm and then is focused on the semiconductor saturable absorption mirror 1, so that the energy of light spots incident on the semiconductor saturable absorption mirror 1 is larger, and the mode locking threshold value is favorably reached; the flat angle end of the bevel angle 4 is connected with the signal input end of the (2+1) × 1 optical fiber beam combiner 6 in a welding mode to form resonance, the pumping source 5 of the semiconductor laser is connected with the pumping end of the (2+1) × 1 optical fiber beam combiner 6 in a mechanical splicing mode, one end of the gain optical fiber 7 is connected with the signal output end of the (2+1) × 1 optical fiber beam combiner 6 in a welding mode, the other end of the gain optical fiber 7 is sequentially connected with the dispersion compensation chirped fiber grating 802 in a welding mode, the polarization controller 9 in a mechanical splicing mode and the microdisk whispering gallery mode optical microcavity 102 in a mechanical splicing mode, the output end of the microdisk whispering gallery mode optical microcavity 102 adopts a mode of directly outputting from the end face of the optical fiber, therefore, the micro-cavity based intermediate infrared Raman ultrafast fiber laser oscillator outputs high-power Raman laser. A band-pass filter 11 with a wave band of 3 microns is connected outside the resonant cavity to obtain the output of the Raman laser with a specific wavelength.
The calcium fluoride microdisk whispering gallery mode optical microcavity 102 is prepared by cutting, grinding, polishing and the like by using high-purity single-crystal calcium fluoride as a basic material. An image of the prepared microdisk whispering gallery mode optical microcavity 102 is shown in FIG. 9, where it can be seen that the diameter is 5 mm, the thickness is 1 mm, and the Q value is 106。
The micro-disk type microcavity coupling mode in the embodiment 2 of the microcavity-based intermediate infrared raman ultrafast fiber laser oscillator is tapered fiber coupling, wherein the tapered fiber 23 is a fluoride fiber, the diameter of the fiber core of the tapered fiber 23 is drawn to about 2 microns in the invention to ensure that enough light is coupled from the tapered fiber 23 to the micro-disk type whispering gallery mode optical microcavity 102, and the coupling ratio is controlled by controlling the distance between the micro-disk type whispering gallery mode optical microcavity 102 and the tapered fiber 23, so that the mode coupling efficiency is high, and the operation is simple.
The micro-cavity-based intermediate infrared Raman ultrafast fiber laser oscillator increases or decreases the length of the gain fiber and adjusts Er of the gain fiber3+The doping concentration can realize the tuning of the central wavelength, and the tuning range is 2.7-2.9 microns. The optical fibers made of different materials are connected in a mechanical splicing mode.
The micro-cavity-based intermediate infrared Raman ultrafast fiber laser oscillator can realize Raman frequency shift in the cavity through the Raman scattering effect of the micro-cavity element. By increasing the coupling efficiency of the pumping power and the microsphere cavity, the control of Raman intensity can be realized, so that the conversion from first-order Raman to high-order Raman is realized, and Raman laser with a wave band of 3 microns and longer can be obtained. And a band-pass filter 11 with a wave band of 3 microns is added at the output end, so that the needed Raman laser with a specific wave band can be obtained.
The microcavity-based intermediate infrared Raman ultrafast fiber laser oscillator can observe a mode-locked pulse diagram through an oscilloscope, the expected mode-locked pulse diagram is shown in figure 10, the pulse mode is stable, and the repetition frequency passes through a formula
And (6) calculating. Where f is the pulse repetition frequency, L represents the optical path length of light once back and forth in the cavity, and c represents the speed of light, 30MHz in example 2. Raman spectra were observed by a spectrometer with a fluoride fiber having a Raman frequency shift of 17.4THz (580 cm)-1). In example 2, a first-order raman laser pattern is expected to be observed around 3430nm on the spectrometer, and a spectrum expected to be obtained is shown in fig. 11. Meanwhile, the pulse width and the substructure of the obtained ultrafast pulse can be further measured using an autocorrelator.
Besides the optical micro-cavity of micro-sphere type or micro-disk type mentioned in the above embodiments, the optical micro-cavity can be one of micro-column type, micro-bubble type, micro-tube type or micro-ring type, as long as the quality factor Q value of the micro-cavity is not less than 106And (4) finishing. Wherein the diameter of the micro-ring type optical microcavity should not be less than 500 microns, so as to ensure that the microcavity has more modes in the gain bandThe number of the formula (II).
Claims (9)
1. The intermediate infrared Raman ultrafast fiber laser oscillator based on the microcavity is characterized by adopting a linear cavity structure and mainly comprising a mode locking element saturable absorber (1), a lens I (2), a lens II (3), a pumping source (5), a fiber combiner (6), a gain fiber (7), a dispersion compensation element, a polarization controller (9) and a high-Q-value microcavity, wherein the high-Q-value microcavity is a whispering-gallery-mode optical microcavity, and the Q value of a quality factor of the microcavity is not lower than 106；
Cutting an oblique angle (4) with an angle alpha of 8-20 degrees at one side of a signal input end of an optical fiber combiner (6), wherein emergent light of the oblique angle (4) vertically irradiates to the center of a lens, namely, one end with an angle of the oblique angle (4) is focused on a mode locking element saturable absorber (1) through two lenses with proper focal lengths, a flat angle end of the oblique angle (4) is connected with the signal input end of the optical fiber combiner (6) to form resonance, a pumping source (5) is connected with a pumping end of the optical fiber combiner (6), one end of a gain optical fiber (7) is connected with a signal output end of the optical fiber combiner (6), the other end of the gain optical fiber (7) is connected with one end of a dispersion compensation element, the other end of the dispersion compensation element is connected with one end of a polarization controller (9), a microcavity (10) with a high Q value is connected behind the polarization controller (9), or the microcavity (10) with a high Q value is connected between the optical fiber combiner, or a high-Q microcavity (10) is connected between the gain fiber (7) and the dispersion compensating element.
2. The microcavity-based mid-infrared raman ultrafast fiber laser oscillator according to claim 1, wherein the high-Q microcavity is one of a microsphere type, a micro-column type, a micro-disk type, a micro-bubble type, a micro-tube type, or a micro-ring type.
3. The microcavity-based mid-infrared raman ultrafast fiber laser oscillator according to claim 1 or 2, wherein the material of the microcavity with a high Q value is one of 2-micron band low-loss quartz or 3-micron band low-loss silicon, germanium, calcium fluoride, zinc selenide mid-infrared low-loss material.
4. The microcavity-based mid-infrared raman ultrafast fiber laser oscillator according to claim 1 or 2, wherein the high-Q microcavity coupling is one of a tapered fiber coupling or a prism-to-free space coupling.
5. The microcavity-based mid-infrared raman ultrafast fiber laser oscillator according to claim 1 or 2, wherein the mode-locking element saturable absorber (1) is one of a semiconductor saturable absorber mirror, a graphene saturable absorber mirror, a carbon nanotube saturable absorber mirror or a graphene oxide saturable absorber mirror, the working range thereof covers a 2-3 μm band, and the modulation depth R is in a range of 8% to 30%.
6. A microcavity-based mid-infrared raman ultrafast fiber laser oscillator according to claim 1 or 2, wherein the pump source (3) is a semiconductor laser pump source with a central wavelength λ of 793nm or 976 nm.
7. The microcavity-based mid-infrared raman ultrafast fiber laser oscillator according to claim 1 or 2, wherein the gain fiber (4) is a rare earth single doped Tm3+Quartz fiber or rare earth ion Tm3+ 、Ho3+Codoped silica optical fibers, or Er3+A doped fluoride optical fiber.
8. A microcavity-based mid-infrared raman ultrafast fiber laser oscillator according to claim 1 or 2, wherein the dispersion compensating element is a dispersion compensating fiber (801) or a chirped fiber grating (802).
9. A microcavity-based mid-infrared raman ultrafast fiber laser oscillator according to claim 1 or 2, further comprising a band-pass filter (11), the band-pass filter (11) being connected outside the resonator.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201910174040.0A CN109755850B (en) | 2019-03-08 | 2019-03-08 | Intermediate infrared Raman ultrafast fiber laser oscillator based on micro-cavity |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201910174040.0A CN109755850B (en) | 2019-03-08 | 2019-03-08 | Intermediate infrared Raman ultrafast fiber laser oscillator based on micro-cavity |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN109755850A CN109755850A (en) | 2019-05-14 |
| CN109755850B true CN109755850B (en) | 2020-01-03 |
Family
ID=66407007
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201910174040.0A Active CN109755850B (en) | 2019-03-08 | 2019-03-08 | Intermediate infrared Raman ultrafast fiber laser oscillator based on micro-cavity |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN109755850B (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111555109B (en) * | 2020-04-16 | 2021-07-06 | 清华大学 | Dissipative gain coupled microcavity system |
| CN113507039B (en) * | 2021-05-13 | 2022-07-08 | 华东师范大学 | Single-mode micro-laser based on single whispering gallery mode optical microcavity and implementation method |
Family Cites Families (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7532656B2 (en) * | 2005-02-16 | 2009-05-12 | The Trustees Of Columbia University In The City Of New York | All-silicon raman amplifiers and lasers based on micro ring resonators |
| US20150314134A1 (en) * | 2014-05-02 | 2015-11-05 | Krzysztof Slawomir Nowicki | Method of generating life sustaining energy in the terminal and respiratory bronchioles system (trbs) |
| CN204927802U (en) * | 2015-07-03 | 2015-12-30 | 安徽大学 | Tunable optical microcavity Raman laser and tunable optical microcavity doped laser |
| CN105024269B (en) * | 2015-07-10 | 2018-08-10 | 北京大学 | A kind of Free Space Optics micro-cavity Raman laser sensor arrangements and its method for sensing |
| CN105731785B (en) * | 2016-04-26 | 2018-08-21 | 江苏师范大学 | A kind of atmosphere protection type chalcogenide glass fiber prick-drawing device and application method |
| CN107046221A (en) * | 2017-02-24 | 2017-08-15 | 南京邮电大学 | A kind of single-frequency narrow band fiber laser based on the high symmetrical microcavity of circularity three-dimensional rotation |
| CN106785861A (en) * | 2017-03-01 | 2017-05-31 | 太原理工大学 | Gao Zhongying ultra-short pulse generation method and device based on Graphene microcavity locked mode |
-
2019
- 2019-03-08 CN CN201910174040.0A patent/CN109755850B/en active Active
Also Published As
| Publication number | Publication date |
|---|---|
| CN109755850A (en) | 2019-05-14 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| Liu et al. | On-chip erbium-doped lithium niobate microcavity laser | |
| Li et al. | Recent progress on mid-infrared pulsed fiber lasers and the applications | |
| Dvoyrin et al. | Efficient bismuth-doped fiber lasers | |
| US9787051B2 (en) | Compact optical frequency comb systems | |
| Peng et al. | Fiber-taper-coupled L-band Er 3+-doped tellurite glass microsphere laser | |
| Kirsch et al. | Short-wave IR ultrafast fiber laser systems: Current challenges and prospective applications | |
| CN108429126B (en) | Thulium-doped microsphere cavity laser and preparation method thereof | |
| WO2012146912A1 (en) | Laser with a tailored axially symmetric pump beam profile by mode conversion a waveguide | |
| Cleff et al. | Femtosecond OPO based on LBO pumped by a frequency-doubled Yb-fiber laser-amplifier system for CARS spectroscopy | |
| CN109755850B (en) | Intermediate infrared Raman ultrafast fiber laser oscillator based on micro-cavity | |
| Jheng et al. | Broadly tunable and low-threshold Cr 4+: YAG crystal fiber laser | |
| Martial et al. | Er: YAG fiber-shaped laser crystals (single crystal fibers) grown by micro-pulling down: Characterization and laser operation | |
| Ren et al. | Ti: Sapphire micro-structures by femtosecond laser inscription: Guiding and luminescence properties | |
| CN113594842A (en) | Device and method for generating ultrashort pulse of erbium-doped laser | |
| CN102332676A (en) | Mid-infrared fiber laser | |
| US20230187894A1 (en) | Tunable microwave source based on dual-wavelength lasing of single optical whispering gallery microcavity | |
| Li et al. | Erbium-ytterbium co-doped lithium niobate single-mode microdisk laser with an ultralow threshold of 1 µW | |
| Singh et al. | Chip-scale, CMOS-compatible, high energy passively Q-switched laser | |
| Sen et al. | High power fiber lasers: Fundamentals to applications | |
| US9341781B2 (en) | Laser machining and mechanical control of optical microresonators | |
| Bae et al. | Er: LiYF4 planar waveguide laser at 2.8 μm | |
| CN108039638B (en) | Low-threshold two-stage spectrum shaping flexible optical fiber high-power mode-locked laser | |
| Wang et al. | Few-mode Cr-doped crystalline core fibers for fiber amplifier | |
| Vukovic et al. | Fast and controllable beam switching in a pulsed fiber laser | |
| CN118315908B (en) | Passive mode-locked fiber laser with polymorphic solitons |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| GR01 | Patent grant | ||
| GR01 | Patent grant | ||
| TR01 | Transfer of patent right | ||
| TR01 | Transfer of patent right |
Effective date of registration: 20240103 Address after: No. 1, Floor 1, Unit 1, Building 9, No. 1, Chengfei Avenue, Qingyang District, Chengdu, Sichuan 610000 Patentee after: Chengdu Liyuan Optoelectronic Technology Co.,Ltd. Address before: 221116 No. 101, Shanghai Road, Copper Mt. New District, Jiangsu, Xuzhou Patentee before: Jiangsu Normal University |