CN105790052A - Method of improving mid-infrared supercontinuum light source slope efficiency and output power - Google Patents
Method of improving mid-infrared supercontinuum light source slope efficiency and output power Download PDFInfo
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/05—Construction or shape of optical resonators; Accommodation of active medium therein; Shape of active medium
- H01S3/06—Construction or shape of active medium
- H01S3/063—Waveguide lasers, i.e. whereby the dimensions of the waveguide are of the order of the light wavelength
- H01S3/067—Fibre lasers
- H01S3/06708—Constructional details of the fibre, e.g. compositions, cross-section, shape or tapering
- H01S3/06716—Fibre compositions or doping with active elements
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/05—Construction or shape of optical resonators; Accommodation of active medium therein; Shape of active medium
- H01S3/06—Construction or shape of active medium
- H01S3/063—Waveguide lasers, i.e. whereby the dimensions of the waveguide are of the order of the light wavelength
- H01S3/067—Fibre lasers
- H01S3/06708—Constructional details of the fibre, e.g. compositions, cross-section, shape or tapering
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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
- H01S3/06754—Fibre amplifiers
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/09—Processes or apparatus for excitation, e.g. pumping
- H01S3/091—Processes or apparatus for excitation, e.g. pumping using optical pumping
- H01S3/094—Processes or apparatus for excitation, e.g. pumping using optical pumping by coherent light
- H01S3/0941—Processes or apparatus for excitation, e.g. pumping using optical pumping by coherent light of a laser diode
Abstract
The invention discloses a method of improving mid-infrared supercontinuum light source slope efficiency and output power, so as to solve the problems of low slope efficiency and low power for a mid-infrared supercontinuum generated in a soft glass fiber amplifier. Through designing the mid-infrared supercontinuum light source based on the soft glass fiber amplifier, working wavelengths of two signal sources are selected to be the same as two cascaded radiation transition wavelengths of doped rare earth ions respectively, power amplification is carried out on the signal light of two wavelengths, and the mid-infrared supercontinuum is generated. Through building the mid-infrared supercontinuum based on the soft glass fiber amplifier, the signal light of two wavelengths is amplified at the same time in the mid-infrared supercontinuum light source to generate supercontinuum output, energy between two adjacent energy levels corresponding to three energy levels is released in a radiation transition form, heat generation can be reduced, and the slope efficiency and the output power of the mid-infrared supercontinuum light source can be improved.
Description
Technical field
The invention discloses a kind of method improving mid-infrared super continuum source slope efficiency and output, belong to laser technology field.
Background technology
Directly producing super continuous spectrums in fiber amplifier is the effective way realizing high power super continuum source.nullAlthough visible light wave range and near infrared band super continuum source technology based on silica-based optical fiber amplifier are comparatively ripe，But it is limited to quartz material in the strong absorption loss of 2.4 μm of band above，The existing long wave limit based on the super continuum source output spectrum of silica-based optical fiber amplifier is difficult to surmount 2.6 μm (referring to W.Yang,B.Zhang,J.Hou,R.Xiao,Z.Jiang,Z.Liu.Mid-IRsupercontinuumgenerationinTm/Hocodopedfiberamplifier[J].LaserPhysicsLetters,2013,10 (5): 055107. (Yang Wei is strong，Tm Ho co doped fiber amplifier produces mid-infrared super continuous spectrums，Laser physics bulletin，2013，10th phase the 5th volume))，Therefore the realization of middle-infrared band super continuum source depends on and adopts phonon energy relatively low、At the relatively low soft glass optical fiber of middle-infrared band absorption loss (such as fluoride glass fiber、Tellurides (includes tellurite) glass optical fiber、Chalcogenide glass optical fiber).Developing the most ripe in current soft glass optical fiber is ZBLAN optical fiber (ZBLAN, i.e. ZrF4-BaF2-LaF3-AlF3-NaF, the one of fluoride fiber component).It addition, when realizing the mid-infrared super continuum source based on soft glass fiber amplifier, must adopt and there is, at 2-5 mu m waveband, the doped fiber that the rare earth ion of radiation transistion is constituted, be erbium doped ion (Er the most widely as currently used3+) or holmium ion (Ho3+) etc. ZBLAN optical fiber, i.e. Er3+: ZBLAN optical fiber and Ho3+: ZBLAN optical fiber.
Relatively immature due to soft glass fiber optic materials technology, and the bad mechanical property of soft glass optical fiber, fusing point is low, intractability is bigger reason, only have one section of open report based on the mid-infrared super continuum source of soft glass fiber amplifier at present, namely at the Er that 976nm is laser diode-pumped3+: repetition rate is by ZBLAN fiber amplifier 2kHz, wavelength 2.75 μm, pulse width 400ps flashlight be amplified, produce the mid-infrared super continuous spectrums of 2.6-4.1 μm (referring to J.Gauthier, V.Fortin, S.Duval, etal.In-amplifiermid-infraredsupercontinuumgeneration [J] .OpticsLetters, 2015,40 (22): 5247-5250. (J.Gauthier etc., fiber amplifier mid-infrared super continuous spectrums produces, optics letter, 2015, the 40th phase the 22nd volume)).But its slope efficiency when the spectrum of super continuous spectrums of output is the widest is only 4.5%, although can pass through to sacrifice spectral width and promote slope efficiency further, but slope efficiency is the highest is also only 7.5%, and power extensibility is poor.In this report, relatively low slope efficiency, while the lifting of restriction super continuous spectrums output, bring serious problem to the heat management of system, stability and reliability.Therefore the slope efficiency of boost amplifier, stability and reliability for promoting the power of the super continuous spectrums of output, the heat load reducing system and then the system of lifting are most important.
The method based on the super continuum source of soft glass fiber amplifier in above-mentioned report is, by designing the super continuum source based on soft glass fiber amplifier, the flashlight of single wavelength is carried out power amplification by soft glass fiber amplifier and realizes the non-linear broadening of spectrum, thus realizing super continuous spectrums output.It is to be noted, for soft glass doped fiber conventional at present, the rare earth ion of its doping may participate in the energy level of radiation transistion and generally have three, and between three energy levels, there is the radiation transistion of two cascades, thus, only the flashlight of single wavelength being amplified and produce super continuous spectrums, one is to cause the super continuous spectrums slope efficiency of the waste of pump energy and amplifier output not high；Two is the energy overwhelming majority form dissipation with multi-phonon decay of waste, produces substantial amounts of heat, and heat management and stability to system cause serious threat.Above-mentioned two aspects limit the lifting of the output of the super continuum source being currently based on soft glass fiber amplifier.
Disclosed technical data is from numerical simulation and the results show, Er3+: ZBLAN optical fiber and Ho3+: ZBLAN fiber optic applications slope efficiency when cascade lasing laser instrument reaches the feasibility of 60%.T.Sumiyoshi et al. reports at Ho3+null: ZBLAN optical fiber produces the experiment of 2.93 μm and 2.06 μm continuous wave cascade laser，The slope efficiency of Output of laser is 52% (referring to T.Sumiyoshi,H.Sekita.Dual-wavelengthcontinuous-wavecascadeoscillationat3and2μmwithaholmium-dopedfluoride-glassfiberlaser[J].OpticsLetters,1998,23 (23): 1837-1839. (TetsumiSumiyoshi etc.，3 μm and 2 μm of continuous wave cascade dual wavelengths mix holmium fluoride fiber laser instrument，Optics letter，1998，23rd phase the 23rd volume))；The slope efficiency of this experiment was promoted to again 65% (referring to T.Sumiyoshi, H.Sekita, T.Arai, etal.High-powercontinuous-wave3-and2-μm of cascadeHo by this group later3+: ZBLANfiberlaseranditsmedicalapplications [J] .IEEEJournalofSelectedTopicsinQuantumElectronics, 1999,5 (4): 936-943. (T.Sumiyoshi etc., 3 μm and 2 μm cascade dual wavelength Ho of High power CW3+: ZBLAN optical fiber laser, high power quantum electronics offprint, 1999, the 5th phase the 4th volume))；J.Li et al. passes through numerical simulation, demonstrates theoretically, at Er3+: ZBLAN optical fiber and Ho3+null: in the optical fiber laser that ZBLAN optical fiber is constituted，Adopt the mode of cascade operating，The slope efficiency of laser instrument all up to more than 60% (referring to J.Li,H.Luo,Y.Liu,etal.Modelingandoptimizationofcascadederbiumandholmiumdopedfluoridefiberlasers[J].SelectedTopicsinQuantumElectronics,IEEEJournal,2014,20 (5): 15-28. (Li Jianfeng etc.，Based on er-doped and cascaded laser numerical simulation and the optimization of mixing holmium fluoride fiber，2014，20th phase the 5th volume)).But the method being at present reported in the amplifier that soft glass doped fiber is constituted still without disclosed technical data to be amplified by the flashlight of dual wavelength and produce super continuous spectrums.
Summary of the invention
The technical problem to be solved in the present invention is the problem that slope efficiency is low, power is low producing mid-infrared super continuous spectrums in soft glass fiber amplifier.The present invention proposes a kind of method improving mid-infrared super continuum source slope efficiency and output, by designing the mid-infrared super continuum source based on soft glass fiber amplifier, the operation wavelength choosing two signal sources respectively is identical with the radiation transistion wavelength of the two of the rare earth ion adulterated cascades, respectively the flashlight of two wavelength is carried out power amplification and produces mid-infrared super continuous spectrums, heat production can be reduced, improve slope efficiency and the output of mid-infrared super continuum source.
Technical scheme comprises the following steps:
The first step, builds a kind of mid-infrared super continuum source based on soft glass fiber amplifier.Described light source is made up of doped fiber, the first signal source, secondary signal source, pumping source, optical coupling assembly, cladding mode stripper.Cladding mode stripper is arranged in doped fiber.Described the first signal source, secondary signal source and pumping source export the first flashlight, secondary signal light, pumping light respectively, first flashlight, secondary signal light, pumping light are coupled in doped fiber through optical coupling assembly, and doped fiber exports super continuous spectrums through cladding mode stripper.
Doped fiber is the double clad soft glass optical fiber doped with rare earth ion.The rare earth ion of doped fiber doping requires there are three energy levels that may participate in radiation transistion under pump wavelength, energy level from low to high respectively the first energy level, the second energy level, three-level, and the transition between three-level and the second energy level, between the second energy level and the first energy level all can realize with the form of radiation transistion；The wavelength that radiation transistion between three-level with the second energy level is corresponding is first wave length λ1, the wavelength that radiation transistion between the second energy level with the first energy level is corresponding is second wave length λ2, the first energy level is wavelength lambda to the absorptive transition wavelength of three-level3, and naturally meet 1/ λ3≥1/λ1+ 1/ λ2.Doped fiber cuts flat with angle near one end of the first signal source and secondary signal source, and doped fiber is away from 8 ° of oblique angles of an end-grain cutting in the first signal source and secondary signal source, the feedback that the Fresnel reflection to eliminate fiber end face brings.The end face processing of doped fiber ensures the Single-end output of super continuum source and suppresses lasing.Doped fiber is the first end near one end of pumping source, and the other end is the second end.
First signal source is single mode pulse optical fiber or the electrical modulation single mode pulsed laser diode with tail optical fiber, and operation wavelength i.e. the first flashlight and λ1Identical, the laser pulse width of transmitting is ns～ps magnitude, and pulse recurrence frequency is kHz～GHz magnitude.First signal source is positioned at one end of doped fiber.First signal source exports the first flashlight, collimates through optical coupling assembly, focuses on, transmits with the form of total reflection and amplify in the fibre core in doped fiber.
Secondary signal source is single mode pulse optical fiber or the electrical modulation single mode pulsed laser diode with tail optical fiber, operation wavelength and secondary signal light and λ2Identical, the laser pulse width of transmitting is ns～ps magnitude, and pulse recurrence frequency is kHz～GHz magnitude.Secondary signal source and the first signal source are positioned at same one end of doped fiber.Secondary signal source output secondary signal light, collimates through optical coupling assembly, focuses on, transmit with the form of total reflection and amplify in the fibre core in doped fiber.
Pumping source is continuous wave multimode laser or the continuous wave multimode laser diode with tail optical fiber, operation wavelength and pumping light and λ3Identical.Pumping source may be located at doped fiber that one end near the first signal source Yu place, secondary signal source, it is also possible to is positioned at the other end of doped fiber.Pumping source output pumping light, collimates through optical coupling assembly, focuses on, and with the form transmission of total reflection in the inner cladding in doped fiber, and is being absorbed through doped fiber fibre core.
Optical coupling assembly is made up of the first collimating lens, the second collimating lens, the 3rd collimating lens, the first dichroscope, the second dichroscope, the first coupled lens, the second coupled lens.Optical coupling assembly receive the first flashlight, secondary signal light, pumping light one end be input, outgoing the first flashlight, secondary signal light, pumping light one end be outfan.First signal source, secondary signal source and pumping source are respectively positioned on the input of optical coupling assembly.The outfan of optical coupling assembly is just right with doped fiber.The output tail optical fiber of the first signal source is just placed by the first collimating lens, and makes the output tail optical fiber end face of the first signal source be positioned at the focal point of the first collimating lens；The output tail optical fiber in secondary signal source is just placed by the second collimating lens, and makes the output tail optical fiber end face in secondary signal source be positioned at the focal point of the second collimating lens；The output tail optical fiber of pumping source is just placed by the 3rd collimating lens, and makes the output tail optical fiber end face of pumping source be positioned at the focal point of the 3rd collimating lens.First wave length is had the absorbance of more than 98% by the first collimating lens, by the first flashlight collimation of the first signal source output.First wave length and second wave length are had the absorbance of more than 98% by the second collimating lens, the secondary signal light collimation exported in secondary signal source.3rd wavelength is had the absorbance of more than 98% by the 3rd collimating lens, pumping light collimation pumping source exported.First collimating lens and the second collimating lens are mutually perpendicular to placement, thus through the first flashlight light beam of the first collimating lens collimation and the secondary signal light beam orthogonal through the second collimating lens collimation.First dichroscope in the optical path with collimation after the first flashlight light beam and secondary signal light beam path angle all at 45 ° place.First wave length is had the reflectance of more than 98% by the first dichroscope, and second wave length has the absorbance of more than 98%；The first flashlight after collimation and secondary signal light are merged into light beam by the first dichroscope.3rd collimating lens is vertical with the second collimating lens to be placed, thus the pumping light light beam through the 3rd collimating lens collimation and the first flashlight through the first dichroscope conjunction bundle and secondary signal light beam orthogonal.Second dichroscope in the optical path with collimation after pumping light light beam and close the first flashlight of bundle and secondary signal light light beam angle all at 45 ° is placed through the first dichroscope.3rd wavelength is had the reflectance of more than 98% by the second dichroscope, and the first flashlight and secondary signal light have the absorbance of more than 98%；Pumping light after collimation is merged into light beam with the first flashlight closed through the first dichroscope after restrainting and secondary signal light by the second dichroscope.First coupled lens just to the second collimating lens, and the second parallel placement of collimating lens, and make doped fiber be positioned at the focal point of the first coupled lens near the fiber end face of the first signal source and one end, secondary signal source；First flashlight, secondary signal light, pumping light are had the absorbance of more than 98% by the first coupled lens；The light of the above three wavelength closed after restrainting is focused on, is coupled in doped fiber by the first coupled lens.Second coupled lens is just to one end away from the first signal source and secondary signal source of doped fiber, and makes doped fiber be positioned at the focal point of the second coupled lens away from the fiber end face of the first signal source and one end, secondary signal source；The light of pump light wavelength and 2-5 mu m waveband is had the absorbance of more than 98% by the second coupled lens；The super continuous spectrums collimation output that second coupled lens will produce.In optical coupling assembly the position relationship of all parts ensure that light from the first signal source, secondary signal source, pumping source to the coupling efficiency of doped fiber more than 90%.
Cladding mode stripper is the second end at doped fiber, and one section of doped fiber divests coat and surrounding layer, and is coated with refractive index match cream and makes, and wherein, the doped fiber length divesting coat and surrounding layer is n centimetre, 1≤n≤5.Refractive index match cream to the refractive index of pumping light lower than refractive index to pumping light of the inner cladding of doped fiber.Cladding mode stripper makes doped fiber the second end not absorb pumping light completely and leaks out doped fiber, it is ensured that without pumping light component in the super continuous spectrums of output.It is above the basic scheme (forward direction pumping scheme) of light source.
In order to improve the output of super continuum source further, the present invention also can adopt the scheme of backward pump, namely pumping light is coupled into doped fiber away from one end of signal source through optical coupling assembly from doped fiber, first and second flashlight and pumping light reverse transfer in doped fiber.Therefore, pumping source in this programme, the 3rd collimating lens, the second dichroscope should be positioned at doped fiber one end away from the first signal source and secondary signal source, and the relative position between pumping source, the 3rd collimating lens, the second dichroscope is identical with relative position between pumping source, the 3rd collimating lens, the second dichroscope in basic scheme；3rd collimating lens and the second coupled lens are mutually perpendicular to placement so that the pumping light collimated through the 3rd collimating lens is coupled into doped fiber through the second coupled lens.It addition, be positioned at the definition of doped fiber the second end according to cladding mode stripper, namely it be positioned at doped fiber one end away from pumping source, thus in this programme, cladding mode stripper is positioned at doped fiber one end near the first signal source and secondary signal source.In this programme, the super continuous spectrums collimation that the second coupled lens will produce, the super continuous spectrums coupling output that the second coupled lens and the second dichroscope will produce jointly.
In order to reduce the use of space device in super continuum source, and improving the stability that super continuum source works, the first collimating lens, the first dichroscope by the scheme with wavelength division multiplexer, namely can also be substituted by the present invention with optical fibre wavelength division multiplexer.The first input end of optical fibre wavelength division multiplexer is operated in first wave length λ1, the second input of optical fibre wavelength division multiplexer is operated in second wave length λ2, the outfan of optical fibre wavelength division multiplexer is operated in first wave length λ1With second wave length λ2。
In order to both improve the output of super continuum source, reduce again the use of space device in super continuum source, improve the stability of super continuum source work, the present invention can also adopt backward pump the scheme with optical fibre wavelength division multiplexer, namely, while adopting backward pump, with optical fibre wavelength division multiplexer, the first collimating lens, the first dichroscope are substituted.
Second step, the mid-infrared super continuum source based on soft glass fiber amplifier produces super continuous spectrums:
2.1 produce the first flashlight, secondary signal light and pumping light.First signal source and secondary signal source export the first flashlight and secondary signal light respectively；Pumping source output pumping light, pumping light is collimated by the 3rd collimating lens；
First flashlight, secondary signal light are entered doped fiber with pumping optical coupling by 2.2.The difference of the structure according to super continuum source, is divided into following four situation:
2.2.1 when adopting basic scheme (forward direction pumping scheme), the first flashlight collimate by the first collimating lens, and the second collimating lens is to secondary signal light collimation, the first flashlight after the first dichroscope collimation and secondary signal combiner；Second dichroscope is by the pumping light after collimation and closes the first flashlight after restrainting and secondary signal combiner through the first dichroscope.The first flashlight closed after restrainting, secondary signal light, pumping light are focused on and are coupled into doped fiber by the first coupled lens.Turn 2.3.
2.2.2 when adopting backward pump scheme, the first flashlight collimate by the first collimating lens, and the second collimating lens is to secondary signal light collimation, the first flashlight after the first dichroscope collimation and secondary signal combiner；The first flashlight closed after restrainting, secondary signal light are focused on and are coupled into doped fiber by the first coupled lens.Second dichroscope is by the pumping luminous reflectance after collimation, and the pumping light of reflection is focused on and is coupled into doped fiber by the second coupled lens.Turn 2.3.
2.2.3, when adopting with the scheme of optical fibre wavelength division multiplexer, optical fibre wavelength division multiplexer is by the first flashlight and secondary signal combiner and is exported by the output tail optical fiber of optical fibre wavelength division multiplexer；First flashlight and the secondary signal light of output are collimated by the second collimating lens；Second dichroscope by through second collimating lens collimation after the first flashlight and secondary signal light and through the 3rd collimating lens collimation after pumping combiner；The first flashlight closed after restrainting, secondary signal light, pumping light are focused on and are coupled into doped fiber by the first coupled lens.Turn 2.3.
2.2.4, when adopting backward pump and with the scheme of optical fibre wavelength division multiplexer, optical fibre wavelength division multiplexer is by the output tail optical fiber of the first flashlight and secondary signal combiner to optical fibre wavelength division multiplexer and exports；First flashlight and the secondary signal light of output are collimated by the second collimating lens；The first flashlight after collimation, secondary signal light are focused on and are coupled into doped fiber by the first coupled lens；Second dichroscope is by the pumping luminous reflectance after the 3rd collimating lens collimation, and the pumping light of reflection is focused on and is coupled into doped fiber by the second coupled lens.Turn 2.3.
2.3 power amplifications, produce and output super continuous spectrums.
2.3.1 power amplification.The inner cladding of doped fiber is with the form transmission pumping light of total reflection；The fibre core of doped fiber absorbs the pumping light through fibre core, and transmits with the form of total reflection and amplify the first flashlight and secondary signal light.The power (mean power and peak power) of the first flashlight and secondary signal light is constantly amplified by doped fiber.Detailed process is: the pumping light that pumping source produces will be in the rare earth ion pumping of the first energy level to three-level by excited absorption, and forms population inversion between three-level and the second energy level；Owing to wavelength and the three-level of the first flashlight are identical to the radiation transistion wavelength of the second energy level, thus the first flashlight when transmitting in doped fiber, stimulated radiation will be there is, namely one is in the rare earth ion of three-level under the induction of a first flashlight photon to the second energy level transition, gives off one and the identical photon of this photon simultaneously；Therefore when the first flashlight transmits in doped fiber, power will be continuously available amplification, peak power constantly promotes, and the rare earth ion of three-level constantly transits to the second energy level by stimulated radiation process simultaneously, and forms population inversion between the second energy level and the first energy level.Equally, owing to wavelength and second energy level of secondary signal light are identical to the radiation transistion wavelength of the first energy level, thus secondary signal light when transmitting in doped fiber, stimulated radiation will be there is, namely one is in the rare earth ion of the second energy level under the induction of a secondary signal light photon to the first energy level transition, gives off one and the identical photon of this photon simultaneously；Therefore when secondary signal light transmits in doped fiber, power will be continuously available amplification, and peak power constantly promotes, and the rare earth ion of the second energy level constantly transits to the first energy level by stimulated radiation process simultaneously.And the rare earth ion of the first energy level is constantly by pumping optical pumping to three-level, the gain population of three-level is constantly replenished, thus the process of power amplification is continued.
2.3.2 produce and output super continuous spectrums.When the peak power of the first flashlight and secondary signal light is amplified to more than the threshold power of nonlinear effect by doped fiber, the pulse of the first flashlight and secondary signal light is due to the strong effect of nonlinear effect in doped fiber, and spectrum respectively obtains broadening；Due to the alternating action of power amplification and nonlinear effect in doped fiber, the power of the light producing in doped fiber and transmitting improves constantly, and the continuous broadening of spectrum ultimately forms high-power mid-infrared super continuous spectrums.Cladding mode stripper will not absorb after pumping light filters completely in inner cladding, mid-infrared super continuous spectrums is exported by one end (namely away from one end of the first signal source and secondary signal source) of the sharping of doped fiber.
2.4 collimation mid-infrared super continuous spectrums.The difference of the organization plan according to super continuum source, is divided into following four situation:
2.4.1 when adopting basic scheme (forward direction pumping scheme), the mid-infrared super continuous spectrums collimation that one end of the sharping of doped fiber is exported by the second coupled lens.
2.4.2, when adopting backward pump scheme, the mid-infrared super continuous spectrums collimation that one end of the sharping of doped fiber is exported by the second coupled lens, the second dichroscope is by the mid-infrared super continuous spectrums transmission of collimation.
2.4.3 when adopting the scheme with optical fibre wavelength division multiplexer, the mid-infrared super continuous spectrums collimation that one end of the sharping of doped fiber is exported by the second coupled lens.
2.4.4 when adopting backward pump and with the scheme of optical fibre wavelength division multiplexer, the mid-infrared super continuous spectrums collimation that one end of the sharping of doped fiber export by the second coupled lens, the mid-infrared super continuous spectrums transmission that the second dichroscope will collimate.
Adopt the present invention can reach techniques below effect:
The present invention is by building a kind of mid-infrared super continuum source based on soft glass fiber amplifier, this mid-infrared super continuum source amplifies the flashlight of two wavelength simultaneously and produces super continuous spectrums output, energy between two corresponding for three energy levels adjacent energy levels is all passed through the form release of radiation transistion, compared with the flashlight of single wavelength being amplified in soft glass fiber amplifier at present and then produce the method for mid-infrared super continuous spectrums, the present invention can improve slope efficiency and the output of mid-infrared super continuum source.
Accompanying drawing explanation
Fig. 1 is overview flow chart of the present invention.
Fig. 2 is the schematic diagram of basic scheme (forward direction pumping scheme) of what the first step built mid-infrared super continuum source.
Fig. 3 is simplification level structure and excited absorption, the stimulated radiation transition schematic diagram of mid-infrared super continuum source Rare Earth Ion provided by the invention.
Fig. 4 is the schematic diagram of backward pump scheme of what the first step built mid-infrared super continuum source.
Fig. 5 is the schematic diagram of the scheme with optical fibre wavelength division multiplexer of what the first step built mid-infrared super continuum source.
Fig. 6 is the schematic diagram of what the first step built the backward pump of mid-infrared super continuum source scheme with optical fibre wavelength division multiplexer.
Specific embodiments
Fig. 1 is for being overview flow chart of the present invention.The first step is to build a kind of mid-infrared super continuum source based on soft glass fiber amplifier.Second step is based on the mid-infrared super continuum source of soft glass fiber amplifier and produces super continuous spectrums.Second step comprises four sub-steps, is respectively as follows: 2.1 generation the first flashlights, secondary signal light and pumping light；First flashlight, secondary signal light are entered doped fiber with pumping optical coupling by 2.2；2.3 power amplifications and generation and output mid-infrared super continuous spectrums；2.4 collimation mid-infrared super continuous spectrums.
Fig. 2 is the schematic diagram of basic scheme (forward direction pumping scheme) of what the first step of the present invention built mid-infrared super continuum source.Described light source is made up of doped fiber the 1, first signal source 2, secondary signal source 3, pumping source 4, optical coupling assembly 5, cladding mode stripper 6.Cladding mode stripper 6 is arranged in doped fiber 1.Described the first signal source 2, secondary signal source 3 and pumping source 4 export the first flashlight, secondary signal light, pumping light respectively, first flashlight, secondary signal light, pumping light are coupled in doped fiber 1 through optical coupling assembly 5, and doped fiber 1 exports super continuous spectrums through cladding mode stripper 6.
Doped fiber 1 can be selected for the Er of double clad3+: ZBLAN optical fiber or Ho3+: ZBLAN optical fiber.The Er of doping3+Or Ho3+Three energy levels that may participate in radiation transistion are had under pump wavelength, energy level from low to high respectively the first energy level, the second energy level, three-level, and the transition between three-level and the second energy level, between the second energy level and the first energy level all can realize with the form of radiation transistion；The wavelength that radiation transistion between three-level with the second energy level is corresponding is first wave length λ1, the wavelength that radiation transistion between the second energy level with the first energy level is corresponding is second wave length λ2, the first energy level is wavelength lambda to the absorptive transition wavelength of three-level3, and naturally meet 1/ λ3≥1/λ1+1/λ2.Doped fiber cuts flat with angle near one end of the first signal source 2 and secondary signal source 3, and doped fiber is away from 8 ° of oblique angles of an end-grain cutting in the first signal source 2 and secondary signal source 3, the feedback that the Fresnel reflection to eliminate doped fiber 1 end face brings.The end face processing of doped fiber 1 ensures the Single-end output of super continuum source and suppresses lasing.Doped fiber 1 is the first end near one end of pumping source 4, and the other end is the second end.
First signal source 2 can be selected for single mode pulse optical fiber or the electrical modulation single mode pulsed laser diode with tail optical fiber, and pulse width is ns～ps magnitude, and pulse recurrence frequency is kHz～GHz magnitude, and operation wavelength i.e. the first signal light wavelength and λ1Identical.First signal source 2 launches the first flashlight, collimates through optical coupling assembly 5, focuses on, and transmits with the form of total reflection and amplifies in the fibre core of doped fiber 1.
Secondary signal source 3 can be selected for single mode pulse optical fiber or the electrical modulation single mode pulsed laser diode with tail optical fiber, and pulse width is ns～ps magnitude, and pulse recurrence frequency is kHz～GHz magnitude, operation wavelength and secondary signal optical wavelength and λ2Identical.Secondary signal light is launched in secondary signal source 3, collimates through optical coupling assembly 5, focuses on, and transmits with the form of total reflection and amplifies in the fibre core of doped fiber 1.
Pumping source 4 can be selected for continuous wave multimode laser or the continuous wave multimode laser diode with tail optical fiber, operation wavelength and pump light wavelength and λ3Identical.Pumping source 4 emission pumping light, collimates through optical coupling assembly 5, focuses on, and with the form transmission of total reflection in the inner cladding of doped fiber 1, and is absorbed at the fibre core through doped fiber 1.
Optical coupling assembly 5 is made up of first collimating lens the 51, second collimating lens the 52, the 3rd collimating lens the 53, first dichroscope the 54, second dichroscope the 55, first coupled lens the 56, second coupled lens 57.Optical coupling assembly 5 receive the first flashlight, secondary signal light, pumping light one end be input, outgoing the first flashlight, secondary signal light, pumping light one end be outfan.First signal source 2, secondary signal source 3 and pumping source 4 are respectively positioned on the outfan of optical coupling assembly 5.The outfan of optical coupling assembly 5 is just right with doped fiber 1.The output tail optical fiber of the first signal source 2 is just placed by the first collimating lens 51, and makes the output tail optical fiber end face of the first signal source 2 be positioned at the focal point of the first collimating lens 51；The output tail optical fiber in secondary signal source 3 is just placed by the second collimating lens 52, and makes the output tail optical fiber end face in secondary signal source 3 be positioned at the focal point of the second collimating lens 52；The output tail optical fiber of pumping source 4 is just placed by the 3rd collimating lens 53, and makes the output tail optical fiber end face of pumping source 4 be positioned at the focal point of the 3rd collimating lens 53.First wave length is had the absorbance of more than 98% by the first collimating lens 51, the first flashlight collimation the first signal source 2 exported.Second wave length is had the absorbance of more than 98% by the second collimating lens 52, the secondary signal light collimation exported in secondary signal source 3.3rd wavelength is had the absorbance of more than 98% by the 3rd collimating lens 53, pumping light collimation pumping source 4 exported.First collimating lens 51 and the second collimating lens 52 are mutually perpendicular to placement, thus through the first flashlight light beam of the first collimating lens 51 collimation and the secondary signal light beam orthogonal through the second collimating lens 52 collimation.First dichroscope 54 in the optical path with collimation after the first flashlight light beam and secondary signal light beam path angle all at 45 ° place.First wave length is had the reflectance of more than 98% by the first dichroscope 54, and second wave length has the absorbance of more than 98%；The first flashlight after collimation and secondary signal light are merged into light beam by the first dichroscope 54.3rd collimating lens 53 is vertical with the second collimating lens 52 to be placed, thus the pumping light light beam through the 3rd collimating lens 53 collimation and the first flashlight through the first dichroscope 54 conjunction bundle and secondary signal light beam orthogonal.Second dichroscope 55 in the optical path with collimation after pumping light light beam and close the first flashlight of bundle and secondary signal light light beam angle all at 45 ° is placed through the first dichroscope 54.3rd wavelength is had the reflectance of more than 98% by the second dichroscope 55, and the first flashlight and secondary signal light have the absorbance of more than 98%；Pumping light after collimation is merged into light beam with the first flashlight after the first dichroscope 54 closes bundle and secondary signal light by the second dichroscope 55.First coupled lens 56 just to the second collimating lens 52, and with the second parallel placement of collimating lens 52, and make doped fiber 1 be positioned at the focal point of the first coupled lens 56 near the fiber end face of the first signal source 2 and one end, secondary signal source 3；First flashlight, secondary signal light, pumping light are had the absorbance of more than 98% by the first coupled lens 56；The optical coupling of the above three wavelength closed after restrainting is entered in doped fiber 1 by the first coupled lens 56.Second coupled lens 57 is just to one end away from the first signal source 2 and secondary signal source 3 of doped fiber 1, and makes doped fiber 1 be positioned at the focal point of the second coupled lens 57 away from the fiber end face of the first signal source 2 and one end, secondary signal source 3；The light of 2-5 mu m waveband is had the absorbance of more than 98% by the second coupled lens 57；The super continuous spectrums collimation output that second coupled lens 57 will produce.In optical coupling assembly 5 position relationship of all parts ensure that light from the first signal source 2, secondary signal source 3, pumping source 4 to the coupling efficiency of doped fiber more than 90%.
Cladding mode stripper 6 is by the second end of doped fiber 1, divests one section of coat and surrounding layer, and the refractive index match cream being coated with low-refraction is made.Cladding mode stripper makes doped fiber the second end not absorb pumping light completely and leaks out doped fiber, it is ensured that without pumping light component in the super continuous spectrums of output.
The work process of the mid-infrared super continuum source that the first step of the present invention builds is: described the first signal source 2, secondary signal source 3 and pumping source 4 export the first flashlight, secondary signal light, pumping light respectively, it is coupled in doped fiber 1 through optical coupling assembly 5, doped fiber 1 is to the first flashlight, secondary signal light and is produced mid-infrared super continuous spectrums by nonlinear effect effect, doped fiber 1 exports mid-infrared super continuous spectrums through cladding mode stripper 6, and optical coupling assembly 5 is by the mid-infrared super continuous spectrums collimation of output.
Fig. 3 is simplification level structure and excited absorption, the stimulated radiation transition schematic diagram of the rare earth ion of doping in doped fiber 1 fibre core in the mid-infrared super continuum source that the first step of the present invention builds.It is described in more detail below in conjunction with the physical process in Fig. 3 mid-infrared super continuum source that the first step of the present invention is built.The pumping light that pumping source produces will be in the first energy level E by excited absorption1Rare earth ion pumping to three-level E3(process a), and at three-level E3With the second energy level E2Between formed population inversion；Wavelength and three-level E due to the first flashlight3To the second energy level E2Radiation transistion wavelength identical, thus when the first flashlight transmits in doped fiber 1, stimulated radiation will be there is, namely one is in three-level E3Rare earth ion under the induction of a first flashlight photon to the second energy level E2Transition, gives off one and the identical photon (process b) of this photon simultaneously；Therefore when the first flashlight transmits in doped fiber 1, power will be continuously available amplification, and peak power constantly promotes, simultaneously three-level E3Rare earth ion constantly transit to the second energy level E by stimulated radiation process2, and at the second energy level E2With the first energy level E1Between formed population inversion.Similarly, since the wavelength of secondary signal light and the second energy level E2To the first energy level E1Radiation transistion wavelength identical, thus when secondary signal light transmits in doped fiber 1, stimulated radiation will be there is, namely one is in the second energy level E2Rare earth ion under the induction of a secondary signal light photon to the first energy level E1Transition, gives off one and the identical photon (process c) of this photon simultaneously；Therefore when secondary signal light transmits in doped fiber 1, power will be continuously available amplification, and peak power constantly promotes, simultaneously the second energy level E2Rare earth ion constantly transit to the first energy level E by stimulated radiation process1.And the first energy level E1Rare earth ion again constantly by pumping optical pumping to three-level E3, three-level E3Gain population be constantly replenished, thus the process of power amplification is continued.In the process that first flashlight and secondary signal light peak power constantly promote, when reaching the threshold value of various nonlinear effect (including Self-phase modulation, Cross-phase Modulation, modulational instability, four-wave mixing, stimulated Raman scattering etc.), the very big broadening of spectrum will be produced by nonlinear effect.Power amplification and nonlinear effect constantly interact, and ultimately form high-power super continuous spectrums.By above-mentioned physical process it can be seen that, one pumping light photon can produce the flashlight photon (a first flashlight photon and a secondary signal light photon) of two different wave lengths, and the energy sum of above-mentioned two flashlight photon is little with pumping light photon energy difference, achieve the conversion of pump energy most possibly, thus high slope efficiency can be realized.Simultaneously because the transition between energy level all realizes with the form of radiation transistion, thus the nonradiative transitions such as the multi-phonon decay of generation heat are inhibited, thus the heat production of system greatly reduces.Energy conversion efficiency is high, heat production is few, is all conducive to improving the output of mid-infrared super continuum source.
Fig. 4 is the backward pump scheme of the mid-infrared super continuum source of the first step structure of the present invention.Compared with basic scheme, the present embodiment adopts the mode of backward pump, namely the pumping light of pumping source 4 output is coupled into doped fiber 1 away from one end of the first signal source 2 and secondary signal source 3 through optical coupling assembly 5 from doped fiber 1, first and second flashlight and pumping light reverse transfer in doped fiber 1.Therefore, in this programme, pumping source the 4, the 3rd collimating lens the 53, second dichroscope 55 is positioned at doped fiber 1 one end away from the first signal source 2 and secondary signal source 3, and the relative position between pumping source the 4, the 3rd collimating lens the 53, second dichroscope 55 is identical with Fig. 1, pumping source the 4, the 3rd collimating lens the 53, the 3rd collimating lens 53 and the second coupled lens 57 are mutually perpendicular to placement simultaneously so that the pumping optical coupling that the 3rd collimating lens 53 collimates is entered doped fiber 1 by the second coupled lens 57.Additionally, the definition of the second end of doped fiber 1 it is positioned at according to cladding mode stripper 6, namely it is positioned at doped fiber 1 one end away from pumping source 4, thus in this programme, cladding mode stripper 6 is positioned at doped fiber 1 one end near the first signal source 2 and secondary signal source 3.In this programme, the second coupled lens 57 and the common super continuous spectrums coupling that will produce of the second dichroscope 55 export.Compared with basic scheme, this programme can improve the output of super continuum source further.
The difference of this programme and basic scheme: in basic scheme, owing to adopting forward direction pumping, doped fiber 1 is from the one end near the first signal source 2 and secondary signal source 3 to the one end away from the first signal source 2 and secondary signal source 3, gain coefficient tapers into, signal light power is gradually increased, but it is more and more slower to gather way；In this programme, owing to adopting backward pump, doped fiber 1 is from the one end near the first signal source 2 and secondary signal source 3 to the one end away from the first signal source 2 and secondary signal source 3, and gain coefficient becomes larger, signal light power is gradually increased, but it is more and more faster to gather way.Consider the various losses such as scattering loss when flashlight transmits in doped fiber 1, adopt this programme of backward pump to be more prone to the output of high-power super continuous spectrums compared with basic scheme, the power of the super continuous spectrums of present invention output can be promoted further.
Fig. 5 is the scheme with optical fibre wavelength division multiplexer of the mid-infrared super continuum source of the first step structure of the present invention.Compared with basic scheme, in optical coupling assembly 5, the present embodiment optical fibre wavelength division multiplexer 58 replaces first collimating lens the 51, first dichroscope 54, first flashlight and secondary signal light close bundle output through optical fibre wavelength division multiplexer 58 respectively, then collimate through the second collimating lens 52, and after through the second dichroscope 55 transmission, be coupled into doped fiber 1 through the first coupled lens 56 after.
The difference of this programme and basic scheme: this programme decreases the use of Space Coupling device, simpler compact, is conducive to the stability of raising system.
Fig. 6 is the backward pump of the mid-infrared super continuum source that the first step of the present invention builds with the scheme of optical fibre wavelength division multiplexer.In order to both improve the output of super continuum source, reduce again the use of space device in super continuum source, improve the stability of super continuum source work, compared with scheme described in Fig. 2, the present invention can also replace first collimating lens the 51, first dichroscope 54 with optical fibre wavelength division multiplexer 58 while adopting backward pump mode.
The difference of this programme and basic scheme: this programme had both adopted backward pump, it is more prone to the output of high-power super continuous spectrums, the power of the super continuous spectrums of present invention output can be promoted further, decrease again the use of Space Coupling device, simpler compact, be conducive to the stability of raising system.
Owing to, compared with the basic scheme (Fig. 1) of the mid-infrared super continuum source that the first step of the present invention builds, the scheme representated by Fig. 4 to Fig. 6 is only structurally different, and ultimate principle is identical, and therefore work process repeats no more.
Claims (11)
1. the method improving mid-infrared super continuum source slope efficiency and output, it is characterised in that comprise the following steps:
The first step, build the mid-infrared super continuum source based on soft glass fiber amplifier: described light source is made up of doped fiber (1), the first signal source (2), secondary signal source (3), pumping source (4), optical coupling assembly (5), cladding mode stripper (6), and cladding mode stripper (6) is arranged in doped fiber (1)；First signal source (2), secondary signal source (3) and pumping source (4) launch the first flashlight, secondary signal light, pumping light respectively, first flashlight, secondary signal light, pumping light are coupled in doped fiber (1) through optical coupling assembly (5), export super continuous spectrums through cladding mode stripper (6)；
Doped fiber (1) is the double clad soft glass optical fiber doped with rare earth ion；The rare earth ion that doped fiber (1) adulterates requires there are three energy levels that may participate in radiation transistion under pump wavelength, energy level from low to high respectively the first energy level, the second energy level, three-level, and the transition between three-level and the second energy level, between the second energy level and the first energy level all can realize with the form of radiation transistion；The wavelength that radiation transistion between three-level with the second energy level is corresponding is first wave length λ1, the wavelength that radiation transistion between the second energy level with the first energy level is corresponding is second wave length λ2, the first energy level is wavelength lambda to the absorptive transition wavelength of three-level3, and meet 1/ λ1≥1/λ2+1/λ3；Doped fiber (1) is the first end near one end of pumping source (4), and the other end is the second end；
First signal source (2) is single mode pulse optical fiber or the electrical modulation single mode pulsed laser diode with tail optical fiber, and operation wavelength i.e. the first flashlight and λ1Identical, first signal source (2) is positioned at one end of doped fiber (1), first signal source (2) launches the first flashlight, collimate through optical coupling assembly (5), focus on, the fibre core in doped fiber (1) transmits with the form of total reflection and amplifies；
Secondary signal source (3) is single mode pulse optical fiber or the electrical modulation single mode pulsed laser diode with tail optical fiber, operation wavelength and secondary signal light and λ2Identical, secondary signal source (3) and the first signal source (2) are positioned at same one end of doped fiber (1), secondary signal light is launched in secondary signal source (3), collimate through optical coupling assembly (5), focus on, the fibre core in doped fiber (1) transmits with the form of total reflection and amplifies；
Pumping source (4) is continuous wave multimode laser or the continuous wave multimode laser diode with tail optical fiber, operation wavelength and pumping light and λ3Identical；Pumping source (4) is positioned at doped fiber (1) near that one end at the first signal source (2) and secondary signal source (3) place or the other end being positioned at doped fiber (1), the pumping light that pumping source (4) is launched, collimate through optical coupling assembly (5), focus on, with the form transmission of total reflection in inner cladding in doped fiber (1), and absorbed through doped fiber (1) fibre core；
Optical coupling assembly (5) is made up of the first collimating lens (51), the second collimating lens (52), the 3rd collimating lens (53), the first dichroscope (54), the second dichroscope (55), the first coupled lens (56), the second coupled lens (57)；Optical coupling assembly (5) receive the first flashlight, secondary signal light, pumping light one end be input, outgoing the first flashlight, secondary signal light, pumping light one end be outfan；First signal source (2), secondary signal source (3) and pumping source (4) are respectively positioned on the input of optical coupling assembly (5), and the outfan of optical coupling assembly (5) is just right with doped fiber (1)；The output tail optical fiber of the first signal source (2) is just placed by the first collimating lens (51), and makes the output tail optical fiber end face of the first signal source (2) be positioned at the focal point of the first collimating lens (51)；The output tail optical fiber of secondary signal source (3) is just placed by the second collimating lens (52), and makes the output tail optical fiber end face in secondary signal source (3) be positioned at the focal point of the second collimating lens (52)；The output tail optical fiber of pumping source (4) is just placed by the 3rd collimating lens (53), and makes the output tail optical fiber end face of pumping source (4) be positioned at the focal point of the 3rd collimating lens (53)；The first flashlight collimation that first signal source (2) is exported by the first collimating lens (51)；The secondary signal light collimation that secondary signal source (3) are exported by the second collimating lens (52)；The pumping light collimation that pumping source (4) is exported by the 3rd collimating lens (53)；First collimating lens (51) and the second collimating lens (52) are mutually perpendicular to placement, through the first collimating lens (51) the first flashlight light beam collimated and the secondary signal light beam orthogonal collimated through the second collimating lens (52)；First dichroscope (54) in the optical path with collimation after the first flashlight light beam and secondary signal light beam path angle all at 45 ° place, the first flashlight after collimation and secondary signal light are merged into light beam by the first dichroscope (54)；3rd collimating lens (53) is vertical with the second collimating lens (52) to be placed, through the 3rd collimating lens (53) the pumping light light beam collimated and the first flashlight and the secondary signal light beam orthogonal that close bundle through the first dichroscope (54)；Second dichroscope (55) in the optical path with collimation after pumping light light beam and close the first flashlight of bundle and secondary signal light light beam angle all at 45 ° is placed through the first dichroscope (54), the second dichroscope (55) by the pumping light after collimation with close bundle through the first dichroscope (54) after the first flashlight and secondary signal light be merged into light beam；First coupled lens (56) is just to the second collimating lens (52), and placement parallel with the second collimating lens (52), and doped fiber (1) is made to be positioned at the focal point of the first coupled lens (56) near the fiber end face of the first signal source (2) and secondary signal source (3) one end；The optical coupling of the above three wavelength closed after restrainting is entered in doped fiber (1) by the first coupled lens (56)；Second coupled lens (57) is just to one end away from the first signal source (2) and secondary signal source (3) of doped fiber (1), and makes doped fiber (1) be positioned at the focal point of the second coupled lens (57) away from the fiber end face of the first signal source (2) and secondary signal source (3) one end；The super continuous spectrums collimation output that second coupled lens (57) will produce；
Cladding mode stripper (6) is the second end at doped fiber (1), one section of doped fiber (1) is divested coat and surrounding layer, and be coated with refractive index match cream and make, refractive index match cream to the refractive index of pumping light lower than refractive index to pumping light of the inner cladding of doped fiber (1)；Cladding mode stripper (6) makes doped fiber (1) second end not absorb pumping light completely and leaks out doped fiber (1), it is ensured that without pumping light component in the super continuous spectrums of output；
Such light source is the mid-infrared super continuum source based on soft glass fiber amplifier of forward direction pumping scheme；
Second step, the mid-infrared super continuum source based on soft glass fiber amplifier produces super continuous spectrums:
2.1 produce the first flashlight, secondary signal light and pumping light: the first signal source (2) and secondary signal source (3) export the first flashlight and secondary signal light respectively；Pumping source (4) output pumping light, pumping light is collimated by the 3rd collimating lens (53)；
First flashlight, secondary signal light are entered doped fiber (1) with pumping optical coupling by 2.2, and method is:
First flashlight is collimated by the first collimating lens (51), and secondary signal light is collimated by the second collimating lens (52), the first flashlight after the first dichroscope (54) collimation and secondary signal combiner；Second dichroscope (55) is by the pumping light after collimation and closes the first flashlight after restrainting and secondary signal combiner through the first dichroscope (54)；The first flashlight closed after restrainting, secondary signal light, pumping light are focused on and are coupled into doped fiber (1) by the first coupled lens (56)；
2.3 power amplifications, produce and output super continuous spectrums:
2.3.1 power amplification: the inner cladding of doped fiber (1) is with the form transmission pumping light of total reflection；The fibre core of doped fiber (1) absorbs the pumping light through fibre core, and transmits with the form of total reflection and amplify the first flashlight and secondary signal light；The power of the first flashlight and secondary signal light is constantly amplified by doped fiber (1)；Detailed process is: the pumping light that pumping source (4) produces will be in the rare earth ion pumping of the first energy level to three-level by excited absorption, and forms population inversion between three-level and the second energy level；When first flashlight transmits in doped fiber (1), there is stimulated radiation, namely one is in the rare earth ion of three-level under the induction of a first flashlight photon to the second energy level transition, give off one and the identical photon of this photon simultaneously, when first flashlight transmits in doped fiber (1), power will be continuously available amplification, peak power constantly promotes, the rare earth ion of three-level constantly transits to the second energy level by stimulated radiation process simultaneously, and forms population inversion between the second energy level and the first energy level；Equally, when secondary signal light transmits in doped fiber (1), stimulated radiation occurs, and namely one is in the rare earth ion of the second energy level under the induction of a secondary signal light photon to the first energy level transition, gives off one and the identical photon of this photon simultaneously；Secondary signal light is in doped fiber (1) during transmission, and power will be continuously available amplification, and peak power constantly promotes, and the rare earth ion of the second energy level constantly transits to the first energy level by stimulated radiation process simultaneously；And the rare earth ion of the first energy level is constantly by pumping optical pumping to three-level, the gain population of three-level is constantly replenished, and the process of power amplification is continued；
2.3.2 produce and output super continuous spectrums: when the peak power of the first flashlight and secondary signal light is amplified to more than the threshold power of nonlinear effect by doped fiber (1), the pulse of the first flashlight and secondary signal light is due to the strong effect of nonlinear effect in doped fiber (1), and spectrum respectively obtains broadening；Due to the alternating action of power amplification and nonlinear effect in doped fiber (1), the power of the light producing in doped fiber (1) and transmitting improves constantly, and the continuous broadening of spectrum ultimately forms high-power mid-infrared super continuous spectrums；Cladding mode stripper (6) will not absorb after pumping light filters completely in inner cladding, mid-infrared super continuous spectrums is exported by one end of the sharping of doped fiber (1)；
2.4 collimation mid-infrared super continuous spectrums: the mid-infrared super continuous spectrums collimation that one end of the sharping of doped fiber (1) is exported by the second coupled lens (57).
2. the method improving mid-infrared super continuum source slope efficiency and output as claimed in claim 1, it is characterized in that the mid-infrared super continuum source based on soft glass fiber amplifier that the first step builds adopts backward pump scheme, described pumping source (4), 3rd collimating lens (53), second dichroscope (55) is positioned at doped fiber (1) one end away from the first signal source (2) and secondary signal source (3), 3rd collimating lens (53) and the second coupled lens (57) are mutually perpendicular to placement, the pumping light collimated through the 3rd collimating lens (53) is made to be coupled into doped fiber (1) through the second coupled lens (57)；Cladding mode stripper (6) is positioned at doped fiber (1) one end near the first signal source (2) and secondary signal source (3)；Pumping light is coupled into doped fiber (1) away from one end of signal source through optical coupling assembly (5) from doped fiber (1), first and second flashlight and the common super continuous spectrums coupling output that will produce of pumping light reverse transfer in doped fiber (1), the second coupled lens (57) and the second dichroscope (55)；Now the method that the first flashlight, secondary signal light enter doped fiber (1) with pumping optical coupling is by 2.2 steps: the first flashlight is collimated by the first collimating lens (51), second collimation: secondary signal light is collimated by mirror, the first flashlight after the first dichroscope (54) collimation and secondary signal combiner；The first flashlight closed after restrainting, secondary signal light are focused on and are coupled into doped fiber (1) by the first coupled lens (56)；Second dichroscope (55) is by the pumping luminous reflectance after collimation, and the pumping light of reflection is focused on and be coupled into doped fiber (1) by the second coupled lens (57)；The method of 2.4 step collimation mid-infrared super continuous spectrums is: the mid-infrared super continuous spectrums collimation that one end of the sharping of doped fiber (1) is exported by the second coupled lens (57), the second dichroscope (55) is by the mid-infrared super continuous spectrums transmission of collimation.
3. the method improving mid-infrared super continuum source slope efficiency and output as claimed in claim 1, it is characterized in that the mid-infrared super continuum source forward direction pumping scheme based on soft glass fiber amplifier that the first step builds, adopt optical fibre wavelength division multiplexer (58) to replace the first collimating lens (51), the first dichroscope (54)；Now the first flashlight, secondary signal light and pumping optical coupling are entered the method for doped fiber (1) and are by 2.2 steps: optical fibre wavelength division multiplexer (58) is by the first flashlight and secondary signal combiner and is exported by the output tail optical fiber of optical fibre wavelength division multiplexer (58)；First flashlight and the secondary signal light of output are collimated by the second collimating lens (52)；Second dichroscope (55) will through the second collimating lens (52) collimate after the first flashlight and secondary signal light and through the 3rd collimating lens (53) collimation after pumping combiner；The first flashlight closed after restrainting, secondary signal light, pumping light are focused on and are coupled into doped fiber (1) by the first coupled lens (56)；The method of 2.4 step collimation mid-infrared super continuous spectrums is: the mid-infrared super continuous spectrums collimation that one end of the sharping of doped fiber (1) is exported by the second coupled lens (57).
4. the method improving mid-infrared super continuum source slope efficiency and output as claimed in claim 2, it is characterised in that adopt optical fibre wavelength division multiplexer (58) to replace the first collimating lens (51), the first dichroscope (54)；Now the first flashlight, secondary signal light and pumping optical coupling are entered the method for doped fiber (1) and are by 2.2 steps: optical fibre wavelength division multiplexer (58) is by the output tail optical fiber of the first flashlight and secondary signal combiner to optical fibre wavelength division multiplexer (58) and exports；First flashlight and the secondary signal light of output are collimated by the second collimating lens (52)；The first flashlight after collimation, secondary signal light are focused on and are coupled into doped fiber (1) by the first coupled lens (56)；Second dichroscope (55) will through the pumping luminous reflectance after the 3rd collimating lens (53) collimation, and the pumping light of reflection is focused on and be coupled into doped fiber (1) by the second coupled lens (57)；The method of 2.4 step collimation mid-infrared super continuous spectrums is: the mid-infrared super continuous spectrums collimation that one end of the sharping of doped fiber (1) is exported by the second coupled lens (57), the second dichroscope (55) is by the mid-infrared super continuous spectrums transmission of collimation.
5. the method improving mid-infrared super continuum source slope efficiency and output as claimed in claim 1, it is characterized in that described doped fiber (1) cuts flat with angle near one end of the first signal source (2) and secondary signal source (3), doped fiber (1) is away from 8 ° of oblique angles of an end-grain cutting of the first signal source (2) and secondary signal source (3).
6. the method improving mid-infrared super continuum source slope efficiency and output as claimed in claim 1, it is characterized in that described first signal source (2) and secondary signal source (3) require that the laser pulse width launched is ns～ps magnitude, pulse recurrence frequency is kHz～GHz magnitude.
7. the method improving mid-infrared super continuum source slope efficiency and output as claimed in claim 1, it is characterized in that first wave length is had the absorbance of more than 98% by the first collimating lens (51) in described optical coupling assembly (5), second wave length is had the absorbance of more than 98% by the second collimating lens (52), and the 3rd wavelength is had the absorbance of more than 98% by the 3rd collimating lens (53).
8. the method improving mid-infrared super continuum source slope efficiency and output as claimed in claim 1, it is characterized in that first wave length is had the reflectance of more than 98% by the first dichroscope (54) in described optical coupling assembly (5), second wave length is had the absorbance of more than 98%；3rd wavelength is had the reflectance of more than 98% by the second dichroscope (55), and the first flashlight and secondary signal light have the absorbance of more than 98%；First flashlight, secondary signal light, pumping light are had the absorbance of more than 98% by the first coupled lens (56)；The light of 2-5 mu m waveband is had the absorbance of more than 98% by the second coupled lens (57).
9. the method improving mid-infrared super continuum source slope efficiency and output as claimed in claim 1, it is characterized in that the doped fiber (1) divesting coat and surrounding layer is long for n centimetre, to make cladding mode stripper (6), 1≤n≤5.
10. the method improving mid-infrared super continuum source slope efficiency and output as claimed in claim 1, it is characterised in that described doped fiber (1) selects the Er of double clad3+: ZBLAN optical fiber or Ho3+: ZBLAN optical fiber.
11. raising mid-infrared super continuum source slope efficiency as described in claim 3 or 4 and the method for output, it is characterised in that the first input end of optical fibre wavelength division multiplexer (58) is operated in first wave length λ1, the second input of optical fibre wavelength division multiplexer (58) is operated in second wave length λ2, the outfan of optical fibre wavelength division multiplexer (58) is operated in first wave length λ1With second wave length λ2。
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