Polarization independent liquid crystal waveguides on flexible PDMS substrates

Liquid crystals (LC) and LC-composites can be successfully used in the fabrication of photonic devices to be employed in several applications including sensors, optical communications and imaging systems. Components in guided-wave microstructures operating at low optical and electric powers can be engineered and produced exploiting their excellent electro-optic, thermo-optic and nonlinear optical responses [1]. We have investigated different technological processes to make liquid crystal photonics devices based on silica on silicon [2-5] and glass [6,7] in order to obtain new photonic components for optofluidics circuits [8]. Our latest research activity was focused on light propagation in polydimethylsiloxane (PDMS) channels with LC infiltrated core. Both simulation and experimental results confirmed the presence in such waveguides of a polarization independent light transmission. As a matter of fact, notwithstanding LC typical optical anisotropy, the measure of transmission variation descending from LC molecules reorientation was found less than 0.3 dB, this result being consistent with the simulations and the observations made under a polarizing microscope. This result together with the flexibility of the PDMS channels substrate and the absence of an alignment layer makes the proposed LC waveguides a basic structure for low cost devices, which can be used for optical interconnections or integrated with microfluidic circuits for lab on chip and sensing applications.