Use of Cr:LiSGaF and CKIJSAF for cw diode-pumped Q-switched operation (original) (raw)

CLEO '97., Summaries of Papers Presented at the Conference on Lasers and Electro-Optics

Abstract

Recently, Ce:LiCAF’ and Ce:LiSAF* were found to be tunable UV laser materials suitable for pumping in an all-solid-state approach using the 4th harmonic of diode-pumped Nd lasers. The progress made with the Ce:LiCAF/Ce:LiSAF materials offers numerous advantages3 with respect to all other traditional sources of tunable UV radiation. These include conversion efficiency up to -50%: wide continuous tunability -280-315 nm,5 and high potential for immediate tunable W ultrashort pulse application^.^ This is a strong incentive for further aimed searches for new materials capable of lasing with wide W tunability using solid-state (nonexcimer) direct W pumping. Here we report some empirical criteria worked out for the mentioned searches. Spectroscopic features of Ce3+activated SrAIF,-the crystal (hitherto known as an active medium for tunable NIR laser when activated by Ce3+ ions6) chosen for our investigation based on the above criteria-are described in relevance to its potential as an active medium for an all-solid-state tunable UV laser with direct W pumping. The Ce3+-doped tetragonal SAF (Ce:SAF) crystals were grown from carbon crucibles in an inert (Ar) atmosphere using the BridgmanStockbarger technique. The Ce3+ content (in the melt) varied from 0.05 to 0.8 at .Yo. The polarized absorption spectra for a Ce:SAF sample with doping concentration of -0.5 at .% are indicated in Fig. 1. They display, within the 220-300 nm spectral region, a three-band absorption feature centered around 250 nm with the essentially .Ti.-polarized first Ce3+ 4f-5d absorption band nearly centered at 266 nm. This is ideal for direct solid-state W pumping by the 4th harmonic of a Nd laser. Ce3+ room-temperature, polarized fluorescence spectra for the same Ce:SAF sample excited by frequency-quadrupled output of a Q-switched Nd:YAG laser are shown in Fig. 2. The observed Ce3+ fluorescence lifetime was found to be 31 2 5 ns. Fluorescence spans the spectral region of 280-370 nm; it is practically structureless and centered at 316 nm. The Tand u-polarized components have approxi-

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