Characteristics of photonic time shifters based on switched gratings

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Abstract
A cascade of n independently controlled gratings can be used to route an optical carrier through one of 2 inch evenly spaced time delay paths. The resulting optical systems include digital time shifters for phased arrays with the potential for improving attainable performance in terms of insertion loss, crosstalk, and compactness. We describe results from an effort in which these characteristics of free-space optical time delay system based on switched- volume-diffraction gratings were modeled and investigated experimentally. In one experiment, a 1 by 4 router, which constitutes the front end of a 2-bit photonic time delay circuit, was used to validate the low insertion loss and miniaturization capabilities of this technology. We fabricated electrically switched gratings which demonstrated 20 dB contrast and a response time of 15 microseconds. Realistic loss and crosstalk parameters were used in detailed systems modeling to show that practical system can be built using this technology with very low insertion loss and crosstalk. Various configurations are described, including a multi-pass device that may replace many single channel time shifters with a single optical system.© (1998) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

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