Thermally-induced nonlinear spatial shaping of infrared femtosecond pulses in nematic liquid crystals

TL;DR

This study demonstrates how thermal nonlinear effects in nematic liquid crystals can be used to control the spatial profile of infrared femtosecond pulses, enabling potential applications in ultrafast optical shaping.

Contribution

It reveals the thermal nonlinear response of nematic liquid crystals to femtosecond pulses and explores its potential for spatial beam shaping and device applications.

Findings

Strong spatial self-phase modulation observed

Nonlinearity sign depends on laser polarization

Temperature approaches nematic phase transition

Abstract

An optically-induced thermal non-linear effect in a nematic liquid-crystal (E7) cell is evidenced through weak light-absorption by the ITO coating of an infrared pulsed femtosecond laser (m). Strong spatial self-phase modulation is generated, thus a multiple-ring pattern is observed in the far-field. The sign of the nonlinearity is changed depending on the laser polarization. The refractive index and thermal gradients are measured as a function of the laser intensity and we observe that the temperature can increase close to the nematic phase transition. The fidelity and stability of the process open new prospects for spatial shaping devices and delimits the operating wavelength range for ultrafast liquid-crystal based electro-optic application.