Cov plaub thev naus laus zis no tau tham ua ke vim tias lawv txhua tus cuam tshuam ncaj qha rau cov txiaj ntsig ntawm laser resonance.
1. Hom xaiv:
Kev xaiv hom yog qhov kev xaiv zaus. Feem ntau cov lasers siv ntev resonant kab noj hniav kom tau txais lub zog tso zis ntau dua, uas ua rau laser tso zis ntau hom. Txawm li cas los xij, piv nrog cov qauv kev txiav txim siab dua, cov hom kev hloov pauv tseem ceeb (TEM00 hom) muaj cov yam ntxwv ntawm qhov ci ntsa iab, me me divergence lub kaum ntse ntse, tsis sib xws radial lub teeb siv sib faib, thiab ib leeg oscillation zaus, thiab muaj qhov zoo tshaj plaws spatial thiab cuam tshuam lub cev. Yog li ntawd, ib qho tseem ceeb transverse hom laser yog qhov zoo tshaj plaws coherent lub teeb, uas yog ib qho tseem ceeb heev rau kev siv xws li laser interferometry, spectral tsom xam, thiab laser ua. Txhawm rau ua kom tau raws li cov xwm txheej no, kev ntsuas los txwv cov laser oscillation hom yuav tsum tau txais kev pom zoo los txwv kev ua haujlwm ntawm feem ntau resonant zaus hauv ntau hom lasers, thiab siv hom kev xaiv tshuab kom tau txais ib hom ib zaug ib zaug laser tso zis.
Kev xaiv hom yog muab faib ua ob txoj kev: ib qho yog xaiv ntawm laser longitudinal hom, thiab lwm yam yog xaiv ntawm laser transverse hom. Lub qub muaj kev cuam tshuam ntau dua ntawm cov zis ntau zaus ntawm lub laser thiab tuaj yeem txhim kho kev sib raug zoo ntawm lub laser: tom kawg feem ntau cuam tshuam rau qhov sib xws ntawm lub teeb siv ntawm lub laser tso zis thiab txhim kho qhov ci ntawm lub laser.
Longitudinal hom xaiv: Txhawm rau txhim kho cov monochromaticity thiab coherence ntev ntawm lub teeb beam, nws yog ib qho tsim nyog yuav tsum ua kom lub laser ua haujlwm nyob rau hauv ib hom longitudinal. Txawm li cas los xij, ntau lub lasers feem ntau muaj ntau hom longitudinal oscillating tib lub sijhawm. Yog li ntawd, txhawm rau tsim ib hom ntev ntev laser, yuav tsum siv txoj kev xaiv zaus. Cov txheej txheem muaj xws li: txoj kev luv luv, Fabry-Pulloff etalon method, peb-reflector method, thiab lwm yam.
2) Transverse hom xaiv: Cov xwm txheej rau laser oscillation yog tias qhov nce coefficient yuav tsum ntau dua qhov poob coefficient. Qhov poob tuaj yeem muab faib ua qhov tsis sib xws cuam tshuam nrog kev txiav txim siab hloov pauv thiab lwm yam kev poob tsis cuam tshuam rau hom oscillation. Lub ntsiab ntawm qhov tseem ceeb ntawm kev xaiv hom transverse yog ua kom TEM00 hom mus txog qhov oscillation mob, thaum lub oscillation ntawm lub siab dua-order transverse hom yog suppressed. Yog li ntawd, lub hom phiaj ntawm kev xaiv hom transverse tuaj yeem ua tiav los ntawm kev tswj cov kev sib kis ntawm txhua hom kev txiav txim siab dua. Feem ntau hais lus, tsuav yog TEM01 hom thiab TEM10 hom oscillations uas yog ib qho kev txiav txim siab dua li qhov tseem ceeb hloov pauv tuaj yeem raug txwv, qhov oscillation ntawm lwm hom kev txiav txim siab dua tuaj yeem raug txwv. Cov txheej txheem muaj xws li: aperture method, tsom aperture method thiab concave-convex kab noj hniav, xaiv hom siv Q-switching, thiab lwm yam. Intracavity telescope method,
2. Zaus stabilization:
Tom qab lub laser tau txais ib zaus oscillation los ntawm kev xaiv hom, vim muaj kev hloov pauv hauv cov xwm txheej sab hauv thiab sab nraud, qhov zaus resonant tseem yuav txav mus rau hauv tag nrho cov kab dav. Qhov tshwm sim no hu ua "frequency drift". Vim lub hav zoov ntawm drift, qhov teeb meem ntawm laser zaus stability tshwm sim. Lub hom phiaj ntawm kev ruaj khov zaus yog los sim tswj cov kev tswj tau qhov no kom txo tau lawv qhov cuam tshuam nrog cov zaus oscillation, yog li txhim kho qhov ruaj khov ntawm laser zaus.
Frequency stability muaj ob yam: zaus stability thiab zaus reproducibility. Frequency stability yog hais txog qhov sib piv ntawm qhov zaus drift ntawm lub laser mus rau oscillation zaus thaum lub sij hawm ua hauj lwm tsis tu ncua. Qhov sib piv me me, qhov ntau zaus stability. Frequency reproducibility yog qhov sib txawv ntawm qhov zaus thaum lub laser siv nyob rau hauv ntau qhov chaw. Txoj kev ruaj khov zaus muab faib ua hom passive thiab nquag. Qhov tshwj xeeb zaus stabilization txoj kev yog: Lamb sag method thiab saturation absorption method.
3. Q-hloov:
Feem ntau, lub teeb pulses tso zis los ntawm solid-state mem tes lasers tsis yog ib tug du pulses, tab sis ib theem ntawm me me spike pulses nrog sib txawv siv nyob rau hauv microsecond theem. Lub teeb mem tes ua ntu no kav ntev txog ntau pua microseconds lossis txawm tias ob peb feem kaum ntawm ib thib ob, thiab nws lub zog siab tshaj plaws tsuas yog kaum ntawm kilowatts, uas yog deb ntawm kev ua tau raws li qhov xav tau ntawm cov kev siv tswv yim xws li laser radar thiab laser ntau yam. Vim li no, qee cov neeg tau thov lub tswv yim ntawm Q-hloov, uas tau txhim kho cov txiaj ntsig ntawm laser pulses los ntawm ntau qhov kev txiav txim ntawm qhov loj, compressed lub mem tes dav mus rau qib nanosecond, thiab lub ncov lub zog yog siab li gigawatts.
Q yog hais txog qhov zoo tshaj plaws ntawm lub laser resonant kab noj hniav. Cov qauv qhia tshwj xeeb yog Q=2n * lub zog khaws cia hauv cov kab noj hniav resonant / lub zog poob ib lub voj voog oscillation.
Q-hloov txoj cai: Ib txoj hauv kev yog siv los ua kom lub resonant kab noj hniav nyob rau hauv ib tug high-poob thiab qis-Q tus nqi xeev thaum pib ntawm kev siv. Lub sijhawm no, qhov pib ntawm Laser Oscillation yog ntau heev, nws yuav tsis tsim oscillation tus lej: thaum tus lej inversion tus lej, nws yuav tsis muaj nuj nqis rau lub ncov yog dheev nce, uas yuav ua rau qhov nce ntawm lub laser nruab nrab kom zoo heev tshaj qhov pib thiab tsim oscillations sai heev. Lub sijhawm no, lub zog ntawm cov khoom khaws cia hauv lub xeev metastable yuav hloov mus rau hauv lub zog ntawm photons. Lub photons nce ntawm tus nqi siab heev, thiab lub laser tuaj yeem tso tawm lub laser pulse nrog lub siab ncov lub zog thiab nqaim dav.
Vim tias qhov poob ntawm qhov resonant kab noj hniav muaj xws li kev xav tsis zoo, kev nqus tsis zoo, qhov tsis sib xws, tawg tawg thiab kev sib kis tsis zoo, cov txheej txheem sib txawv yog siv los tswj ntau hom kev poob los tsim cov Q-switching technologies sib txawv. Tam sim no, Q-switching thev naus laus zis yog: acousto-optic Q-switching, electro-optic Q-switching thiab zas Q-switching.
4. Hom xauv:
Q-switching tuaj yeem nthuav dav lub laser pulse dav kom tau txais laser pulses nrog lub mem tes dav ntawm qhov kev txiav txim ntawm microseconds thiab lub zog siab tshaj plaws ntawm qhov kev txiav txim ntawm gigawatts. Hom locking tshuab yog ib qho cuab yeej uas txuas ntxiv hloov kho lub laser nyob rau hauv ib txoj kev tshwj xeeb, yuam cov theem ntawm txhua hom longitudinal oscillating nyob rau hauv lub laser yuav tsum tau kho, kom txhua hom yog coherently superimposed kom tau ib tug ultrashort mem tes. Siv hom xauv tshuab, ultrashort laser pulses nrog lub mem tes dav ntawm qhov kev txiav txim ntawm femtoseconds thiab lub zog siab tshaj qhov kev txiav txim ntawm T watts tuaj yeem tau txais. Hom xauv tshuab ua rau lub zog laser muaj zog heev hauv lub sijhawm thiab tam sim no yog cov thev naus laus zis tshaj plaws kom tau txais lub zog siab tshaj plaws lasers.
Hom-locking txoj cai: Feem ntau, cov lasers uas tsis yog-uniformly broadened ib txwm tsim ntau hom longitudinal. Txij li thaum tsis muaj kev sib raug zoo ntawm zaus thiab thawj theem ntawm txhua hom, cov qauv tsis sib haum xeeb, yog li lub teeb siv hluav taws xob los ntawm ntau hom longitudinal yog incoherent ntxiv ntawm txhua hom longitudinal. Lub teeb pom kev siv hluav taws xob hloov pauv tsis tu ncua raws sijhawm. Hom kev kaw cia tso cai rau ntau hom longitudinal uas yuav muaj nyob rau hauv lub resonant kab noj hniav kom oscillate synchronously, ua kom lub zaus ntawm txhua oscillation hom sib npaug thiab ua rau lawv thawj theem tsis tu ncua, thiaj li hais tias lub laser outputs ib tug luv luv mem tes sib lawv liag nrog tsis tu ncua thiab sib npaug ntawm lub sij hawm.
Mode-locking technology is divided into active mode locking and passive mode locking. Active mode locking: insert a modulator with a modulation frequency v=c/2L into the resonance to modulate the amplitude and phase of the laser output to achieve synchronous vibration of each longitudinal mode. Passive mode locking: insert a dye box with saturated absorption characteristics into the laser cavity. The absorption coefficient of the dye box with saturable absorption characteristics will decrease with the increase of light intensity. In the laser, as the optical pump excites the working material, each longitudinal mode will occur randomly, and the light field will fluctuate in intensity due to their superposition. When some longitudinal modes are coherently enhanced by chance, parts with stronger light intensity appear, while other parts are weaker. These stronger parts are less absorbed by the dye and have little loss. The weaker parts are absorbed more by the dye and become weaker. As a result of the light field passing through the dye many times, the strong and weak parts are clearly distinguished, and eventually these longitudinal mode coherently enhanced parts are selected in the form of narrow pulses. Passive mode locking has certain requirements for the optical properties of the dye box: the absorption line of the dye must be very close to the laser wavelength; the line width of the absorption line must be >= laser kab dav; lub sij hawm so yuav tsum luv dua li lub sij hawm nws yuav siv sij hawm rau lub plawv dhia rov qab mus rau ib zaug.
