Polarization selective hologram-based photonic delay lines

The use of polarization selective holograms as optical signal routing eleme nts for the implementation of photonic delay lines (PDLs) is proposed. A si ngle bit PDL using ferroelectric liquid crystal (FLC) devices as active pol arization switches and polymer dispersed liquid crystal (PDLC) devices as p olarization selective holograms for optical path routing is experimentally demonstrated and characterized. Different within-channel leakage noise filt ers for improved PDL performance are discussed and experimentally demonstra ted. Record high optical signal-to-leakage noise ratios (> 45 dB) are obtai ned for both PDL settings using a combination of the proposed noise filters . An alternative reflective PDL architecture is also proposed. This reflect ive architecture requires half the physical length for each path compared w ith the transmissive design to obtain the same time delays. Other polarizat ion dependent optical router designs based on birefringent-mode nematic liq uid crystal (NLC) devices are also proposed. (C) 1998 Elsevier Science B.V. All rights reserved.