Highly efficient stimulated Raman scattering of sub-picosecond laser pulses in BaWO₄ for 10.6  µm difference frequency generation

Abstract

Transient stimulated Raman scattering (SRS) of 0.3 ps 515 nm laser pulses in B a W O 4 crystal was experimentally demonstrated with efficiency up to ∼ 20 % for the Stokes component with a wavenumber of ∼ 925 c m − 1 in a simple single-pass geometry. This anomalous high efficiency was obtained due to the laser pulse self-phase modulation resulting in spectral broadening and seeding the SRS. The applicability of seed pulse production for a high-pressure sub-picosecond C O 2 laser amplifier via difference frequency generation in L i G a S 2 crystal was numerically verified.

Highly efficient transient stimulated Raman scattering on secondary vibrational mode of BaWO4 crystal due to its constructive interference with self-phase modulation

“…This efficiency is much higher than that for the strongest ν 1 (925 cm −1 ) Raman mode (by ∼2.3 times following from the data in the present work and by ∼1.5 times that in Ref. [13]). A reason for this is clear from the spectra for E p = 1.8 μJ: a much higher part of the incident pump energy is transformed into the SPM-broadened radiation, which does not contribute to seeding the SRS on the ν 1 Raman mode.…”

“…Based on the presented above results and gained knowledge in Refs. [12,13], we propose the following scenario for the information presented above and observed earlier in Refs. [12,13] experimental data.…”

“…[12,13], we propose the following scenario for the information presented above and observed earlier in Refs. [12,13] experimental data. Figure 5 illustrates this scenario.…”

“…All these features look very similar to those observed in Refs. [12,13] for SRS on ν 1 mode. Except for decay of the peaks with increase of E p , these features were accounted for as a result of seeding SRS by the pump spectrally broadened via self phase modulation (SPM).…”

“…Second, the anti-Stokes SRS components were observed neither in this work, nor in Refs. [12,13] because a deviation Δν to the anti-Stokes side (Δν > 0) exists at the trailing part of the pump pulse. Regarding the Stokes side (Δν < 0), when the amplitude of Δν is about the wavenumber of Raman modes ν 2 & ν 1 (curves 1 and 3), the intensity of incident pump pulse is near its maximum and time Δt 1 for interaction of the corresponding seeding signal with the pump pulse (the distance between the vertical dashed lines) is the longest.…”