Abstract

Optical 2 × 2 exchange switches can be utilized as routing elements for optical computing and fiber optic based networking systems. Here we demonstrate a 2 × 2, polarization independent ferroelectric liquid crystal (FLC) optical exchange switch, which can be used for these applications. Based on the nematic liquid crystal switch of Wagner and Cheng,¹ it operates by separating the input beam into two orthogonal polarizations with a polarizing beam splitter. The beams are then directed through a surface stabilized, parallely aligned FLC cell. By applying ±15 V across the cell the optical polarization is either switched or left unaltered. Using a further polarizing beam splitter, the beams are recombined to produce a single unpolarized beam; its direction is determined by whether the FLC was switched or not. Due to its symmetry, this device can operate as a 2 × 2 exchange switch. Preliminary measurements indicate switching speeds of <30 µs at ±15 V with <−16-dB crosstalk primarily as a result of the beam splitter performance. Device component specifications suggest an operational bandwidth of 30 nm either side of the designed wavelength. Better results are expected with faster FLC cells and improved beam splitters. Other novel total internally reflecting FLC switch designs are being investigated that are polarization independent and have extinction ratios similar to the device of Meadows et al.²

© 1989 Optical Society of America