Tshwj xeeb nta ntawm Ultrafast Lasers
Lub sijhawm luv luv mem tes ntev ntawm ultrafast lasers muab cov tshuab no tshwj xeeb uas paub qhov txawv ntawm cov mem tes ntev lossis nruam nthwv dej (CW) lasers. Txhawm rau tsim cov pulses luv luv, yuav tsum muaj qhov dav spectral bandwidth. Cov duab mem tes thiab nruab nrab wavelength txiav txim siab qhov tsawg kawg nkaus bandwidth xav tau los tsim cov mem tes ntawm lub sijhawm tshwj xeeb. Feem ntau, qhov kev sib raug zoo no tau piav qhia los ntawm lub sijhawm khoom siv bandwidth (TBP), uas yog muab los ntawm cov ntsiab lus tsis meej. TBP ntawm Gaussian faib mem tes yog muab los ntawm.
TBPGaussian{{0}}ΔτΔν≈0.441
Δτ yog lub sijhawm mem tes thiab Δv yog qhov zaus bandwidth. Qhov tseem ceeb, qhov sib npaug qhia tau hais tias muaj kev sib raug zoo ntawm cov spectral bandwidth thiab mem tes ntev, uas txhais tau hais tias thaum lub sij hawm mem tes txo qis, bandwidth yuav tsum tau ua kom cov mem tes nce. Daim duab 1 qhia txog qhov tsawg kawg nkaus bandwidth xav tau los txhawb ntau lub sijhawm sib txawv ntawm cov mem tes.
Daim duab 1: Yam tsawg kawg nkaus spectral bandwidth yuav tsum tau txhawb 10 ps (ntsuab), 500 fs (xiav) thiab 50 fs (liab) laser pulses
Daim duab 2: Depiction ntawm nruab nrab lub zog Pavg thiab ncov zog Ppeak rau lub laser nrog mem tes ntev t
Kev sib tw ntawm ultrafast lasers
Qhov dav spectral bandwidth, siab ncov lub zog thiab lub sijhawm luv luv ntawm ultrafast lasers yuav tsum tau tswj kom zoo hauv koj lub cev. Feem ntau, ib qho ntawm qhov yooj yim tshaj plaws ntawm cov teeb meem no los daws qhov teeb meem yog lub laser broad-spectrum output. Yog tias koj tau siv lub sijhawm ntev dua los yog txuas ntxiv yoj lasers yav dhau los, koj cov khoom muag ntawm optics yuav tsis muaj peev xwm xav txog lossis xa tag nrho bandwidth ntawm ultrafast pulses.
Laser Damage Threshold
Ultrafast optics kuj tseem muaj qhov sib txawv thiab nyuaj-rau-nrhiav kev puas tsuaj ntawm laser (LDT) ntau dua li cov khoom siv laser ntau dua (Daim duab 3). Thaum muab optics rau nanosecond pulsed lasers, LDT qhov tseem ceeb feem ntau yog nyob ntawm qhov kev txiav txim ntawm 5-10 J/cm2. Rau ultrafast optics, qhov tseem ceeb ntawm qhov loj no yog xyaum tsis tau hnov dua, vim LDT qhov tseem ceeb yuav muaj feem ntau ntawm qhov kev txiav txim.<1 J/cm2, usually closer to 0.3 J/cm2.
Qhov kev hloov pauv tseem ceeb hauv LDT amplitude rau lub sijhawm sib txawv ntawm cov mem tes yog qhov tshwm sim ntawm lub laser puas mechanism raws li lub sijhawm mem tes. Rau nanosecond lasers los yog ntev pulsed lasers, lub ntsiab mechanism ua rau kev puas tsuaj yog thermal cua sov. Cov txheej txheej thiab cov khoom siv substrate ntawm optics nqus cov xwm txheej photons thiab ua kom sov. Qhov no tuaj yeem ua rau distortion ntawm cov ntaub ntawv lattice. Cov teebmeem xws li thermal expansion, cracking, melting thiab lattice strain yog cov thermal puas mechanisms rau hom laser qhov chaw.
Daim duab 3: Laser kev puas tsuaj rau qhov chaw kho qhov muag, raws li qhia ntawm no, tuaj yeem txo qhov kev ua haujlwm ntawm lub tshuab laser, ua rau nws tsis muaj txiaj ntsig lossis tsis txaus ntshai. Vim lub sijhawm luv luv, cov txheej txheem kev puas tsuaj thaum siv cov lasers ultrafast yog qhov txawv ntawm cov neeg thaum siv cov lasers ntev dua.
Txawm li cas los xij, nrog ultrafast lasers, lub sijhawm mem tes nws tus kheej yog nrawm dua li lub sijhawm ntsuas kub ntawm lub laser mus rau cov khoom siv lattice, thiab yog li ntawd cov teebmeem thermal tsis yog thawj qhov ua rau kev puas tsuaj ntawm laser (Daim duab 4). Hloov chaw, lub ncov lub hwj chim ntawm ultrafast laser hloov cov kev puas tsuaj rau hauv cov txheej txheem nonlinear xws li multiphoton absorption thiab ionization. Qhov no yog vim li cas nws tsis tuaj yeem yooj yim ntsuas LDT qhov ntsuas ntawm nanosecond pulse rau ntawm lub plawv dhia ceev ceev, vim tias lub cev lub cev ntawm kev puas tsuaj txawv. Yog li ntawd, nyob rau hauv tib yam kev mob ntawm kev siv (xws li, wavelength, mem tes ntev, thiab repetition zaus), ib tug optic nrog ib tug txaus siab LDT ntsuam xyuas yuav yog qhov zoo tshaj plaws optic rau koj tej daim ntawv thov. Optics kuaj nyob rau hauv cov xwm txheej sib txawv tsis yog tus sawv cev ntawm qhov ua tau zoo ntawm tib lub optics hauv ib qho system.
Daim duab 4: Laser-induced puas mechanisms rau txawv mem tes ntev
Dispersion thiab Pulse Extension: Pab Pawg Delay Dispersion
Ib qho kev sib tw nyuaj tshaj plaws uas tau ntsib thaum siv ultrafast lasers yog tswj lub sijhawm ntawm ultrashort pulse pib tawm los ntawm lub laser. Ultrafast pulses yog qhov cuam tshuam rau lub sij hawm aberrations, uas ua rau cov mem tes ntev. Qhov no tshwm sim zuj zus thaum lub sijhawm pib mem tes luv luv. Thaum lub lasers ultrafast tuaj yeem tso cov pulses nrog lub sijhawm ntawm 50 vib nas this, nws muaj peev xwm nthuav cov mem tes hauv lub sijhawm los ntawm kev siv cov iav thiab lo ntsiab muag kom xa cov mem tes mus rau qhov chaw lub hom phiaj, lossis tsuas yog xa cov mem tes los ntawm huab cua.
Lub sij hawm no distortion yog suav hais tias siv ib tug metric hu ua pab pawg ncua dispersion (GDD), kuj hu ua thib ob-order dispersion. Qhov tseeb, kuj tseem muaj cov lus txiav txim siab dua uas yuav cuam tshuam rau lub sijhawm ntawm kev faib tawm ntawm ultrafast laser pulses, tab sis hauv kev xyaum nws feem ntau txaus los tshuaj xyuas cov nyhuv ntawm GDD. GDD yog ib tug zaus-nyob ntawm tus nqi uas ntsuas linearly nrog lub thickness ntawm ib tug muab. Kev sib kis optics zoo li lub lens, qhov rais, thiab lub hom phiaj lub rooj sib tham feem ntau muaj qhov zoo GDD qhov tseem ceeb, qhia tias ib zaug compressed lub mem tes tuaj yeem muab qhov kev sib txuas lus optics ntev ntev dua li cov mem tes tawm los ntawm lub tshuab laser. Tsawg zaus (piv txwv li, ntev wavelength) Cheebtsam propagate sai dua cov zaus siab dua (ie, luv wavelength) Cheebtsam. Raws li cov mem tes mus los ntawm ntau thiab ntau qhov teeb meem, lub wavelengths nyob rau hauv mem tes yuav txuas ntxiv mus nyob rau hauv lub sij hawm. Rau luv luv mem tes ntev, thiab yog li ntawd wider bandwidths, cov nyhuv no yog ntxiv exaggerated thiab tuaj yeem ua rau lub sijhawm pulse tseem ceeb distortion.
Rau ntev pulses nrog nanosecond lossis txawm tias picosecond mem tes ntev, GDD tsis yog qhov teeb meem loj. Txawm li cas los xij, rau luv luv femtosecond pulses, txawm tias muab 10 hli tuab daim N-BK7 hauv txoj kab nqaj tuaj yeem nthuav dav 50 fs pulse nyob nruab nrab ntawm 800 nm los ntawm ntau dua 12%, uas yog kwv yees sib npaug rau tso ob lub qhov rais lossis lim hauv beam txoj kev.
Qhov cuam tshuam ntawm GDD ntawm ib daim ntawv thov yog nyob ntawm ntau yam, suav nrog lub sijhawm siv mem tes (τ input), qhov nruab nrab zaus (lossis wavelength), thiab cov khoom siv los ntawm cov mem tes propagates.
Qhov sib npaug (2) qhia meej meej tias rau tib tus nqi ntawm GDD, lub sijhawm luv luv ntawm pulse yuav nthuav dav dua li lub sijhawm ntev ntawm cov khoom siv mem tes. Qhov no yog vim li cas GDD tsis tau tham hauv cov ntsiab lus ntawm nanosecond lossis picosecond pulses. Piv txwv li, GDD tsuas yog 20,000 fs2 tuaj yeem nthuav dav 1ps mem tes los ntawm 0.2%. Cov piv txwv hauv cov kab lus hauv qab no qhia tau hais tias qhov no sib npaug rau kev nthuav tawm 1030 nm mem tes rau ntau tshaj 1 m ntawm fused silica.
Lub refractive Performance index ntawm ib yam khoom nyob ntawm seb qhov zaus ntawm lub teeb mus los ntawm nws, thiab GDD muaj qhov zoo sib xws ntawm qhov ntsuas qhov taw qhia. Thaum xaiv cov kis tau tus mob thiab refraction optics rau ultrafast systems, fused silica feem ntau pom zoo vim nws muaj ib qho ntawm qhov qis tshaj GDD qhov tseem ceeb nyob rau hauv qhov pom thiab ze-infrared wavelength ranges. Piv txwv li, propagating ib 1030 nm mem tes los ntawm 1 hli ntawm fused silica yuav tsim ib tug GDD ntawm txog 19 fs2, tab sis nyob rau tib lub wavelength, 1 hli ntawm SF11 yuav ua rau GDD ntau tshaj 125 fs2 Refractive index databases, xws li refractivendex. .info, yog ib qho khoom siv tau zoo rau kev txiav txim siab cov khoom siv twg yog qhov zoo tshaj plaws optics siv rau hauv kev xaiv beam, thiab koj cov GDD sau tau yog qhov muaj txiaj ntsig zoo.
Vim tias qhov sib txawv ntawm qhov zoo ntawm GDD thiab lub sijhawm warping, nws tau pom zoo kom siv tshwj xeeb ultrafast optics uas tsim me ntsis kom tsis muaj GDD ntxiv, yog li txo lub sijhawm rau ncua sij hawm mem tes.
Koj yuav paub li cas yog tias koj xav tau mem tes compression?
Thaum twg koj xav tau (re) compress lub laser mem tes? Nyob rau hauv daim ntawv thov ultrafast imaging xws li multiphoton microscopy, qhov muag plooj dluab qhia tau hais tias lub mem tes yuav stretched nyob rau hauv lub sij hawm. Hauv kev ua laser ultrafast, pulse stretching tuaj yeem ua rau txo qhov raug thiab precision. Stretched mem tes ntev txo qhov tshwm sim ntawm multiphoton kev sib cuam tshuam, uas txo cov efficiency ntawm ultrafast system. Txawm hais tias nws tsis tuaj yeem muab cov cai nruj thiab ceev rau txhua qhov xwm txheej, cov piv txwv hauv qab no suav nrog pab qhia qee qhov kev coj ua zoo tshaj plaws rau kev txiav txim siab seb puas yuav tsum tau siv cov mem tes compression.
Xav txog kev teeb tsa multiphoton microscope nrog txoj kab nqaj raws li pom hauv daim duab 5.
Daim duab 5: Piv txwv schematic ntawm txoj kab nqaj hauv kev sim multiphoton microscopy
Qhov kev txiav txim thawj zaug ntawm kev nthuav dav ntawm cov mem tes tuaj yeem tau txais los ntawm kev suav cov GDD kev koom tes ntawm tag nrho cov ntsiab lus hauv lub cev ua ntej lub laser mus txog tus qauv. Cia peb xav tias lub ntsiab contributors rau dispersion yog lub beam expander, lub dichroic lim thiab lub hom phiaj tsom. Peb yuav tsis quav ntsej cov txiaj ntsig ntawm daim iav tsom iav vim lawv feem ntau ua los ntawm cov hlau tsis tshua muaj GDD. Yog tias cov mem tes nyob nruab nrab ntawm lub wavelength ntawm 1030 nm, lub kaw lus tuaj yeem yooj yim ntxiv ntau dua 600 fs2 ntawm GDD.
Seb puas los yog tsis tus mem tes hauv lub cev yuav tsum tau compressed nyob ntawm lub sij hawm input mem tes thiab cov kev xav tau tshwj xeeb ntawm daim ntawv thov. Yog tias koj pib nrog 150fs mem tes, kev sib kis los ntawm optics yuav muaj qhov cuam tshuam tsis zoo rau lub sijhawm mem tes. Txawm li cas los xij, yog tias koj daim ntawv thov xav tau qhov kev daws teeb meem ntawm lub cev uas tuaj yeem ua tiav nrog 10 fs laser pulse, ces qhov nyiaj ntawm GDD yuav ua rau koj pib mem tes nthuav dav mus txog 167 fs. Hauv qhov no, recompression yog yuav tsum tau. Cov ntsiab lus meej no yog nyob ntawm koj txoj kev teeb tsa tshwj xeeb thiab daim ntawv thov.
Ultrafast Laser Daim Ntawv Thov
Spectroscopy
Spectroscopy tau yog ib qho ntawm cov ntawv thov tseem ceeb ntawm ultrafast laser teeb qhov chaw txij li thaum lawv qhia. Los ntawm kev txo cov mem tes ntev mus rau femtoseconds lossis txawm attoseconds, cov txheej txheem dynamic hauv physics, chemistry thiab biology uas keeb kwm tsis tuaj yeem soj ntsuam tam sim no ua tau. Ib qho ntawm cov txheej txheem tseem ceeb yog atomic motion, kev soj ntsuam uas tau txhim kho kev nkag siab txog kev tshawb fawb ntawm cov txheej txheem tseem ceeb xws li molecular vibration, molecular dissociation thiab lub zog hloov pauv hauv cov proteins photosynthetic.
Bioimaging
Ultrafast lasers nrog lub siab ncov lub zog txhawb cov txheej txheem nonlinear thiab txhim kho kev daws teeb meem rau bioimaging, xws li multiphoton microscopy (Fig. 12). Nyob rau hauv ib tug multiphoton system, ob photons yuav tsum sib tshooj nyob rau hauv qhov chaw thiab lub sij hawm nyob rau hauv thiaj li yuav tsim ib tug nonlinear teeb liab los ntawm ib tug lom nruab nrab los yog fluorescent lub hom phiaj. Cov txheej txheem nonlinear no txhim kho cov duab daws teeb meem los ntawm kev txo cov teeb liab fluorescence keeb kwm yav dhau los uas cuam tshuam kev tshawb fawb ntawm ib leeg-photon txheej txheem. Daim duab 13 qhia txog qhov yooj yim teeb liab keeb kwm yav dhau. Qhov me me excitation cheeb tsam ntawm multiphoton microscopy kuj tiv thaiv phototoxicity thiab minimizes kev puas tsuaj rau cov qauv.
Daim duab 6: Multiphoton lossis nonlinear microscopy siv lub laser ultrafast laser los ntes cov duab peb-dimensional (3D) high-resolution nrog txo photobleaching thiab phototoxicity piv rau cov pa confocal microscopy cov tswv yim.
Daim duab 7: Teeb pom kev zoo ntawm ob-photon ob-photon (sab saum toj) thiab ib-photon (hauv qab) microscopy system. Qhov sib tshooj tsim los ntawm ob lub photons ua rau lub ntim me me, thaum lub teeb liab ib leeg-photon cuam tshuam los ntawm cov teeb liab keeb kwm yav dhau los ntawm sab nraum lub dav hlau focal.
Laser cov khoom ua
Ultrafast laser qhov chaw kuj tau hloov kho laser micromachining thiab cov ntaub ntawv ua haujlwm vim yog txoj hauv kev tshwj xeeb uas ultrashort pulses cuam tshuam nrog cov ntaub ntawv. Raws li tau hais ua ntej, thaum tham txog LDT, lub sijhawm ntev ntawm cov mem tes ultrafast sai dua li lub sijhawm ntsuas ntawm thermal diffusion rau hauv cov khoom lattice. Ultrafast lasers tsim ib cheeb tsam me me uas cuam tshuam ntau dua li nanosecond pulsed lasers, ua rau qis kerf poob thiab ua tiav ntau dua. Lub hauv paus ntsiab lus no tseem siv tau rau daim ntawv thov kev kho mob, qhov twg qhov kev txiav txim siab ntawm ultrafast laser yuav pab txo qis kev puas tsuaj rau cov ntaub so ntswg thiab txhim kho cov neeg mob kev paub thaum lub sijhawm phais laser.
Attosecond pulses: yav tom ntej ntawm ultrafast lasers
Raws li kev tshawb fawb mus rau kev nce qib ultrafast lasers txuas ntxiv, tshiab thiab txhim kho lub teeb pom kev zoo nrog lub sijhawm luv luv tau tsim. Txhawm rau kom nkag siab txog cov txheej txheem ntawm lub cev sai dua, ntau tus kws tshawb fawb tau tsom mus rau tiam ntawm attosecond pulses - nyob rau hauv huab cua ultraviolet (XUV) wavelength range, attosecond pulses yog txog 10-18 s. Attosecond pulses tso cai rau kev taug qab ntawm electron motion thiab txhim kho peb txoj kev nkag siab ntawm cov qauv hluav taws xob thiab quantum mechanics. Thaum kev koom ua ke ntawm XUV attosecond lasers rau hauv cov txheej txheem kev lag luam tseem tsis tau txais txiaj ntsig tseem ceeb, kev tshawb fawb tsis tu ncua thiab kev nce qib hauv thaj chaw yuav luag yeej thawb cov thev naus laus zis no tawm ntawm lub chaw sim thiab mus rau hauv kev tsim khoom, raws li tau hais nrog femtosecond thiab picosecond laser qhov chaw.
