LIQUID CRYSTAL-BASED OPTICAL-TIME DELAY UNITS FOR PHASED-ARRAY ANTENNAS

Novel two-dimensional (2-D) spatial light modulator (SLM)-based optica l time delay units (OTDU's) using free-space/solid optics and fiber de lays are introduced for phased array antenna and wideband signal proce ssing applications. In particular, the mature nematic liquid crystal ( NLC) SLM technology is considered for the proposed architectures. A 1x 2 optical switch is demonstrated using a parallel-rub birefringent-mod e NLC cell, a bulk optics cube polarizing beamsplitter, and a sheet po larizer. Switch measurements taken at 633 nm show a > 3400: 1 or > 35 dB output port optical isolation. The 1x2 NLC switch is used to build a 1-bit, 3.33-ns-duration, free-space OTDU using mirrors and total int ernal reflection corner prisms. The unit demonstrated a > 30 dB optica l (or > 60 dB electrical) signal-to-noise ratio for both delay and no- delay positions. A 1500 pixel NLC SLM is built, and a 128: 1 or 21 dB on/off isolation is demonstrated limited by the digital drive electron ics of thin-film transistor (TFT)-based pixel control.