Signature of the Raman self-frequency shift on the autocorrelation of sub-20-fs pulses from Colquiriite lasers

摘要

Summary form only given. A general, dispersion independent result for ultrashort pulses from Colquiriite fs-lasers is a frequency downshifted and asymmetric spectrum. This observation was accounted for by the Raman effect in the laser crystal. Contrary to fiber spectra the Raman spectrum of crystals shows only few narrow lines, thus some initial bandwidth is required to excite the phonons with a resonant beat frequency. According to recent measurements of the Raman spectrum of Cr:LiSGaF, the onset of the frequency shift is possible for a bandwidth exceeding about 40 nm, which agrees with experimental observations. Experimental data were recorded with a standard diode-pumped KLM-LiSAF laser, which was dispersion compensated with LaKL21 prisms.