April 2000 Meeting

The Optical Society of San Diego and this evening's host, Maurice Pessot, are pleased to present a talk by Professor Shaya Fainman, with the Electrical and Computer Engineering department at UCSD entitled "Nonlinear Spatio-Temporal Processing."

Nonlinear Spatio-Temporal Processing
Professor Shaya Fainman

Optical information processing, traditionally employed in the spatial domain, has been experiencing a renaissance with femtosecond laser pulse technology. Temporal optical information can now be manipulated via linear and nonlinear processes, and stored and retrieved, by converting optical signals between the spatial and temporal domains. We will review the activities in spatio-temporal optical signal processing techniques for information data coding, data conversion, signal recording, as well as signal characterization. Applications of these techniques for future computing, communication, storage, and signal processing systems will be discussed.

Biography: Shaya Y. Fainman received the Ph. D. degree from Technion-Israel Institute of Technology in 1983. He is a Professor of Electrical and Computer Engineering at the University of California, San Diego. His current research interests are in programmable and multifunctional diffractive and nonlinear optics, artificial dielectrics and near field optical interactions, space-time processes using femtosecond laser pulses for quantum cryptography and communication. He contributed over 90 manuscripts in referred journals and over 170 presentations and conference proceedings. He is a Fellow of the Optical Society of America and recipient of the Miriam and Aharon Gutvirt Prize. He served on several conferences program committees, organized symposium and workshops. Currently, he is a Topical Editor of the Journal of the Optical Society of America:A on Optical Signal Processing and Imaging Science.

April OSSD Meeting Review
by Maurice Pessot

Our speaker at the April OSSD meeting was Dr. Shaya Fainman of the UCSD School of Electrical and Computer Engineering. Dr. Fainman's topic for the evening was "Nonlinear Spatio-Temporal Processing" (NSTP). NSTP is an optical signal processing technique which utilizes femtosecond pulse sources to enable the conversion of spatial and temporal information form one domain to the other.

Dr. Fainman's talk opened with a discussion of the unique properties of femtosecond lasers and the variety of areas to which they are being applied, including biomedical optics, micromachining, and optical signal processing. Within the context of optical communications, Dr. Fainman noted that the paradigm in favor at the moment is wavelength division multiplexing (WDM), whereby each user is connected by a dedicated wavelength of narrow bandwidth, as opposed to time division multiplexing, in which spectral allocation is broad and the data rates are high. This is dictated by the inability to multiplex many high speed data streams. Nonlinear spatio-temporal processing solves this last problem, enabling the coding of many parallel data channels into a sequence of pulses, and vice-versa.

The space-to-time encoding process is accomplished with a 4F lens arrangement similar to conventional optical signal processing, but with diffraction grating s at the input and output planes. An input pulse is spectrally decomposed and interacts with a filter in the intermediate spatial plane to produce a sequence of ouptut pulses. The produces a space-to-time conversion. To produce a time-to-space conversion a data stream and a reference pulse again enter the processor, but now a nonlinear material in the filter plane encodes the data stream onto the sum frequency generated by the nonlinear crystal. Because this interaction occurs in the plane where the pulse trains are spectrally and spatially decomposed, a time-to-space encoding occurs.

An interesting communications application of this technology is optical code division multiple access (OCDMA) networks. In conjunction with other faculty at UCSD, Dr. Fainman showed how NSTP lends itself naturally to an OCDMA network architecture, and that an OCDMA network provides an intrinsically higher level of security than traditional WDM or TDM optical networks.

Anyone interested in learning more about Dr. Fainman's work, please visit the Ultrafast and Nanoscale Optics website at http://topaz.ucsd.edu.