[PDF]  https://doi.org/10.3952/physics.v60i4.4357

Open access article / Atviros prieigos straipsnis
Lith. J. Phys. 60, 217–224 (2020)
 

LiSAF: AN EFFICIENT AND DURABLE NONLINEAR MATERIAL FOR SUPERCONTINUUM GENERATION IN THE ULTRAVIOLET
Agnė Šuminienė, Vytautas Jukna, Rosvaldas Šuminas, Gintaras Tamošauskas, Mikas Vengris, and Audrius Dubietis
  Laser Research Center, Vilnius University, Saulėtekio 10, 10223 Vilnius, Lithuania
Email: audrius.dubietis@ff.vu.lt

Received 9 September 2020; accepted 11 September 2020

We have experimentally studied supercontinuum generation in an undoped LiSAF crystal using ultraviolet, visible and near infrared pump pulses provided by fundamental and second harmonics of amplified femtosecond Ti:sapphire and Yb:KGW lasers. We have found that the optical degradation of the crystal, manifested by gradual narrowing of the supercontinuum spectrum, starts much faster using infrared pump pulses. This is attributed to the role of impact ionization, which increases with increasing the pump wavelength. The most reliable operation is achieved with the shortest pump wavelength of 400 nm (the second harmonic of a Ti:sapphire laser), where LiSAF produces a stable, almost 1.3 octave-spanning supercontinuum spectrum with a short-wavelength cut-off at 252 nm and shows no apparent optical degradation for one hour of continuous operation at 500 Hz repetition rate without crystal translation.
Keywords: supercontinuum generation, femtosecond filamentation, ultraviolet
PACS: 42.65.Re, 42.65.Jx, 42.70.-a

LiSAF: EFEKTYVI IR PATVARI MEDŽIAGA SUPERKONTINUUMUI GENERUOTI ULTRAVIOLETINĖJE SPEKTRO SRITYJE
Agnė Šuminienė, Vytautas Jukna, Rosvaldas Šuminas, Gintaras Tamošauskas, Mikas Vengris, Audrius Dubietis

Vilniaus universiteto Lazerinių tyrimų centras, Vilnius, Lietuva
Eksperimentiškai ištirtas superkontinuumo generavimas nelegiruotame LiSAF kristale žadinant ultravioletiniais, regimaisiais ir infraraudonaisiais femtosekundiniais pirmosios ir antrosios Ti:safyro ir Yb:KGW lazerių harmonikų impulsais. Parodyta, kad naudojant infraraudonuosius žadinimo impulsus kristalo optinė degradacija, pasireiškianti kaip laipsniškas superkontinuumo spektro siaurėjimas, prasideda daug sparčiau. Tai vyksta dėl smūginės jonizacijos, kuri didėja didėjant žadinimo bangos ilgiui. Patikimiausias veikimas stebėtas naudojant trumpiausio bangos ilgio (400 nm) žadinimo impulsus (antroji Ti:safyro lazerio harmonika), kai LiSAF kristale generuojamas stabilus, beveik 1,3 optinės oktavos pločio superkontinuumo spektras su trumpabangiu nukirtimu ties 252 nm, o netransliuojamas kristalas optiškai nedegraduoja vieną valandą esant 500 Hz impulsų pasikartojimo dažniui.
 
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