Liquid crystals (LC) offer numerous prospects in photonics, for instance, nematics LC-based electro-optical devices enables tunable phase-shifting of optical and THz radiations, or phase-sensing. Indium-Tin-Oxide (ITO) is one of the most employed electrode coating for this applications, thanks to its good transmission in the visible part of the optical spectrum. However, extension towards infrared wavelengths finds some difficulties, such as ITO strong absorption and nonlinear behavior around 1.55µm. Although some optimized versions of ITO are available in this spectral range, with a remaining weak absorption might have a significant impact on the LC optical answer. We demonstrate that an infrared femtosecond oscillator focalized up to 7.6kW/cm2, undergoes strong spatial self-phase modulation in a 180µm thick E7 nematic mixture cell, due to partial laser light absorption (20%) in the yet optimized ITO coating. The heat absorption in the ITO layer is transferred to the nematic layer and a well-confined thermal gradient is established due to the different heat transfer coefficients.

© 2019 IEEE

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