Thermal lensing effect of CS₂ studied with femtosecond laser pulses

Abstract

By chopping 820 nm 18 femtosecond (fs)-laser pulses, continuously generated by a self-mode locked Ti:Al2O3 laser at 82 MHz, into trains with both train-width and train-to-train separation considerably longer than the thermal diffusivity time constant τth of CS2, we conducted Z-scan measurements on it at various times relative to the leading pulse of each train (T's). As a result, we observed negative nonlinear refraction strengthening with T within τth and gradually stabilizing with T exceeding τth. We quantitatively explain the experimental results in terms of the thermal lensing effect. In particular, we attribute the heat generation to non-radiative relaxation of libration excited by individual 18 fs-pulses via stimulated Raman scattering. In contrast to the commonly held view of multi-photon excitation, we propose and verify a new heat-generating mechanism for the thermal lensing effect in CS2.

Generation of infrared photon pairs by spontaneous four-wave mixing in a CS2-filled microstructured optical fiber

“…In the non-degenerate case, generated photon pairs are well separated from both the residual pump photons and the spontaneous Raman scattering (SpRS). Raman lines of CS 2 (656 cm and 800 cm ) 59 for different pump wavelengths are shown in Fig. 2 c. Furthermore, guiding light in the CS 2 core contributes to a reduction of the Raman noise in photon-pair generation.…”

“…By adequately choosing the pump wavelength for the SFWM process, we avoid the two Raman lines of CS 2 (656 cm and 800 cm ) 59 . Raman lines of CS 2 for different pump wavelengths are shown in Fig.…”