Thermal Characterization of the Birefringence of Nematic Liquid Crystals for the Design of Widely-tunable LC-VCSELs

In this work, the thermo-optical properties of nematic liquid crystals are investigated through localized reflectance spectra measurements performed on a tunable LC-filter. The final aim is to insert such LC in the cavity of a tunable VCSEL device, in which local self-heating due to optical or electrical pumping must be taken into account. We demonstrate that, whereas standard LC E7 is not suited for real device operation, the maximal operating temperature of QYDPLC-36 LC is 95°C, with a birefringence at 1.55 μm higher than 0.18 at 60°C.