Txoj kev ncaj tshaj plaws ntawm kev tsim cov pulses laser yog ntxiv ib qho modulator sab nraud rau lub laser txuas ntxiv. Txoj kev no ua rau cov pulses sai npaum li picoseconds, uas yog qhov yooj yim tab sis pov tseg lub zog kho qhov muag, thiab lub zog siab tsis tuaj yeem tshaj lub zog kho qhov muag txuas ntxiv. Yog li ntawd, ib txoj kev ua tau zoo dua ntawm kev tsim cov laser pulses yog intracavity modulation, qhov twg lub zog yog khaws cia ntawm lub sijhawm tawm ntawm qhov tawg thiab tso tawm ntawm lub sijhawm.
Plaub txoj kev siv los tsim cov pulses los ntawm kev hloov kho nyob rau hauv lub laser kab noj hniav yog nce kev hloov, Q-hloov (tsis hloov), kab noj hniav inversion, thiab hom-locking.
Tau txais switching generates luv pulses los ntawm modulating lub twj tso kua mis zog. Piv txwv li, diode nce-hloov lasers muaj peev xwm tsim cov pulses nyob rau hauv thaj tsam ntawm ob peb nanoseconds mus rau ib puas picoseconds los ntawm kev hloov kho tam sim no. Txawm hais tias lub zog pulse tsawg, txoj kev no yog qhov hloov tau yooj yim, piv txwv li, muab cov zaus re-frequency thiab pulse dav. Cov kws tshawb fawb ntawm University of Tokyo tau tshaj tawm txog femtosecond nce-switched semiconductor laser hauv xyoo 2018, qhia txog kev ua tiav hauv 40-xyoo thev naus laus zis bottleneck.
Lub zog nanosecond pulses feem ntau yog tsim los ntawm Q-hloov lasers, qhov twg lub laser yog tawm nyob rau hauv ob peb lub voj voog nyob rau hauv kab noj hniav, nrog rau cov mem tes energies nyob rau hauv ntau ntawm ob peb millijoules mus rau ob peb joules, nyob ntawm seb qhov loj ntawm lub system.
Lub zog nruab nrab (feem ntau hauv qab 1 μJ) picosecond thiab femtosecond pulses yog tsim los ntawm hom-locked lasers, nrog ib lossis ntau dua ultrashort pulses tam sim no nyob rau hauv ib lub voj nruam nyob rau hauv lub laser resonant kab noj hniav, nrog rau cov intracavity pulses emitted ib tug ntawm ib lub sij hawm los ntawm cov zis. coupling daim iav, thiab nrog ib tug rov zaus uas yog feem ntau nyob rau hauv qhov ntau ntawm 10 MHz txog 100 GHz. Daim duab hauv qab no qhia tau hais tias tag nrho-ib txwm dispersion (ANDi) dissipative soliton femtosecond fiber ntau laser teeb, uas tuaj yeem tsim nrog feem ntau ntawm Thorlabs 'tus qauv cov khoom (fiber, lens, mount, thiab hloov chaw).
Cavity inversion cov tswv yim tuaj yeem siv tau ob qho tib si rau Q-hloov lasers kom tau txais luv luv pulses thiab rau hom-locked lasers kom nce lub zog mem tes ntawm qis dua zaus.
Sijhawm thiab Zaus Domain Pulses
Cov duab linear ntawm tus mem tes dhau lub sij hawm feem ntau yooj yim thiab tuaj yeem qhia tau tias yog Gaussian thiab sech² muaj nuj nqi. Pulse duration (tseem hu ua mem tes dav) feem ntau yog qhia raws li ib nrab-dav-high-magnitude (FWHM) tus nqi, piv txwv li, qhov dav spanned los ntawm optical hwj chim ntawm tsawg kawg yog ib nrab ntawm lub ncov hwj chim; luv nanosecond pulses yog tsim los ntawm Q-hloov lasers, thiab ultrashort pulses (USPs) ntawm ob peb kaum ntawm picoseconds rau femtoseconds yog tsim los ntawm hom-locked lasers. Cov khoom siv hluav taws xob siab ceev tuaj yeem ntsuas tsuas yog ob peb kaum ntawm picoseconds ntawm qhov ceev tshaj plaws, thiab luv luv pulses tsuas yog ntsuas tau nrog kev pab los ntawm cov txheej txheem kho qhov muag xws li autocorrelators, FROGs, thiab Kab laug sab.
Yog tias cov duab mem tes paub, kev sib raug zoo ntawm lub zog mem tes (Ep), lub zog siab (Pp), thiab mem tes dav (𝜏p) raug xam raws li qhov sib npaug hauv qab no:
qhov twg fs yog tus coefficient ntsig txog cov duab ntawm cov mem tes, uas yog kwv yees li {{0}}.94 rau Gaussian pulses thiab 0.88 rau sech² pulses tab sis feem ntau yog kwv yees li 1.
Lub bandwidth ntawm tus mem tes tuaj yeem qhia tau raws li qhov zaus, wavelength, lossis angular zaus. Yog tias qhov bandwidth me me, lub wavelength thiab zaus bandwidths hloov dua siab tshiab siv cov kab zauv hauv qab no, qhov twg λ thiab ν yog qhov nruab nrab wavelength thiab zaus, raws li, thiab Δλ thiab Δν yog bandwidth nyob rau hauv wavelength thiab zaus, feem.
Bandwidth Limit Pulse
Rau ib qho tshwj xeeb pulse zoo, lub mem tes muaj qhov tsawg tshaj plaws spectral dav hauv qhov tsis muaj chirp, uas yog hu ua bandwidth-limited los yog Fourier-transform-limited pulse, qhov khoom ntawm lub sij hawm mem tes thiab zaus bandwidth yog qhov tas li, uas yog hu ua time-bandwidth product (TBP). Cov khoom ntawm lub sij hawm mem tes thiab zaus bandwidth yog qhov tsis tu ncua hu ua lub sij hawm-bandwidth khoom (TBP). Lub sij hawm-bandwidth khoom ntawm bandwidth-limited Gaussian thiab sech² pulses yog hais txog 0.441 thiab 0.315, ntsig txog; qhov tseeb chirp ntawm cov mem tes thiab cov pab pawg sib txuas-qhib dispersion tuaj yeem xam los ntawm qhov no.
Yog li ntawd, cov mem tes dav dav yuav tsum tau dav dua Fourier spectra. Piv txwv li, 10 fs mem tes yuav tsum muaj qhov bandwidth tsawg kawg yog qhov kev txiav txim ntawm 30 THz, thaum lub sij hawm attosecond mem tes muaj qhov bandwidth ntau dua, thiab nws qhov nruab nrab zaus yuav tsum zoo tshaj qhov pom lub teeb zaus.
Yam cuam tshuam rau pulse dav
Thaum nanosecond los yog ntev pulses propagate nrog me me los yog tsis muaj kev hloov nyob rau hauv mem tes dav, txawm nyob deb deb, ultrashort pulses tuaj yeem cuam tshuam los ntawm ntau yam:
Chromatic dispersion tuaj yeem ua rau lub plawv dhia loj, txawm hais tias lawv tuaj yeem rov ua dua nrog qhov sib txawv dispersion, raws li qhia hauv daim duab hauv qab no, uas qhia txog kev ua haujlwm ntawm Thorlabs Femtosecond Pulse Compressor los them nyiaj rau microscope dispersion.
Nonlinearities feem ntau tsis cuam tshuam ncaj qha rau lub mem tes dav, tab sis lawv tuaj yeem ua rau cov bandwidths dav dua thiab ua rau cov mem tes muaj kev cuam tshuam rau kev tawg hauv kev nthuav tawm.
Txhua hom fiber ntau (nrog rau lwm qhov kev tshaj tawm nrog kev txwv bandwidth) tuaj yeem cuam tshuam rau lub bandwidth lossis cov duab ntawm ultrashort mem tes, thiab kev txo qis hauv bandwidth tuaj yeem ua rau lub sijhawm nthuav dav; tseem muaj cov xwm txheej uas muaj zog chirped pulses muaj luv luv pulse widths raws li lub spectrum narrows.
