Electro-optical control of polarization in femtosecond-laser written waveguides using an embedded liquid crystal cell

By incorporating a liquid crystal layer into waveguides created through direct laser writing, a tunable waveplate in a fused silica waveguide is successfully realized. In the experiment, a voltage is applied to the birefringent liquid crystal layer, inducing changes in the internal molecular arrangement of the nematic liquid crystal (NLC). Owing to the voltage-induced rotation of the NLC molecules, the polarization of the transmitted light becomes dependent on the applied external electric field. This novel approach to polarization manipulation paves the way for a new family of reconfigurable devices and complex photonic circuits based upon femtosecond-written waveguides.