Todd L. Harris

Spatial-spectral holographic correlator at 1536 nm using 30-symbol quadriphase- and binary-phase-shift keyed codes.

Optical 30-symbol quadriphase-shift keyed (QPSK) and binary-phase-shift keyed (BPSK) codes were processed in a spatial-spectral holographic correlator with the Er(3+): Y(2)SiO(5) spectral hole-burning material operating at 1536 nm in the important 1550-nm communications band. The results demonstrate the ability of spatial-spectral holographic correlators to process QPSK codes and BPSK codes with the same apparatus. The high-fidelity correlations produced by this optical coherent transient device exhibit the low sidelobe characteristics expected for the codes used.

Multigigahertz range-Doppler correlative signal processing in optical memory crystals

Analog optical signal processing of complex radio-frequency signals for range-Doppler radar information is theoretically described and experimentally demonstrated using crystalline optical memory materials and off-the-shelf photonic components. A model of the range-Doppler processing capability of the memory material for the case of single-target detection is presented. Radarlike signals were emulated and processed by the memory material; they consisted of broadband (> 1 GHz), spread-spectrum, pseudorandom noise sequences of 512 bits in length, which were binary phase-shift keyed on a 1.9 GHz carrier and repeated at 100 kHz over 7.5 ms. Delay (range) resolution of 8 ns and Doppler resolution of 130 Hz over 100 kHz were demonstrated.

Demonstration of real-time address header decoding for optical data routing at 1536??nm

We have demonstrated real-time decoding of 20-bit biphase-coded address header pulses, using stimulated photon echoes in a phase-matched crossed-beam configuration. This decoding is one of the functions required for coherent transient optical data routing, packet switching, and processing. The active medium used was single-crystal Y(2)SiO(5) doped with Er(3+), which provides an operating wavelength of 1536 nm.

Chirped excitation of optically dense inhomogeneously broadened media using Eu 3+ :Y 2 SiO 5

Novel pump-probe experiments provide practical, sensitive diagnostics of media inversion by linearly chirped optical pulses. Maxwell-Bloch simulations and Landau-Zener calculations support the experiments and provide a general prescription for inversion of hole-burning media by chirps.

Analog optical signal processing of baseband codes in Tm:YAG up to 10 Gb/s

Aspects of analog signal processing are explored using baseband codes from 1 to 10 Gb/s modulated onto a 378 THz optical carrier and processed by spectral holographic techniques in Tm:YAG. Results include processing of signals buried in additive noise, variation of time delays over 5 /spl mu/s, and material signal losses as low as /spl sim/1 dB//spl mu/s.

Multigigahertz range-Doppler correlative processing in crystals

Spectral-spatial holographic crystals have the unique ability to resolve fine spectral features (down to kilohertz) in an optical waveform over a broad bandwidth (over 10 gigahertz). This ability allows these crystals to record the spectral interference between spread spectrum waveforms that are temporally separated by up to several microseconds. Such crystals can be used for performing radar range-Doppler processing with fine temporal resolution. An added feature of these crystals is the long upper state lifetime of the absorbing rare earth ions, which allows the coherent integration of multiple recorded spectra, yielding integration gain and significant processing gain enhancement for selected code sets, as well as high resolution Doppler processing. Parallel processing of over 10,000 beams could be achieved with a crystal the size of a sugar cube. Spectral-spatial holographic processing and coherent integration of up to 2.5 Gigabit per second coded waveforms and of lengths up to 2047 bits has previously been reported. In this paper, we present the first demonstration of Doppler processing with these crystals. Doppler resolution down to a few hundred Hz for broadband radar signals can be achieved. The processing can be performed directly on signals modulated onto IF carriers (up to several gigahertz) without having to mix the signals down to baseband and without having to employ broadband analog to digital conversion.

A spatial-spectral holographic correlator at 1536 nm using 30-symbol BPSK and QPSK codes optimized for secure communications

Summary form only given. Spatial-spectral holographic devices combine spectral hole burning with conventional holography to perform correlations and other signal processing and memory functions in real time and are ideally suited to process multi-phase encoded information. Such devices can operate at bandwidths greater than 10 GHz, have time-bandwidth products of 10/sup 3/ to 10/sup 5/ and can potentially enhance optical telecommunications capabilities. Employing Er/sup 3+/:Y/sub 2/SiO/sub 5/, we demonstrate excellent signal fidelity in the important telecommunications band around 1550 nm. We further believe this to be the maximum number of symbols yet achieved for correlations with optimized codes.