A proof-of-concept technique has been developed for measuring and controlling the individual phases of array elements. Electro-optic steering and beam-forming of laser beams is an emerging field with devices such as optical phased arrays that are capable of steering with significantly reduced noise floors and that are faster by orders of magnitude.

One of the most difficult aspects of realizing an optical phased array is the phasing of the individual elements that make up the array. The path length of each individual element must be controlled with accuracy on the order of a nanometer. For a multi-element array, this becomes increasingly complex and bulky as the size of the array increases.

Digitally enhanced interferometry (DI) achieves phase measurement and control of each array element using a single detector. Instead of individually sensing the phase of each element on a separate detector, DI separates out each of the element phases digitally by employing pseudo-random codes to separate the elements. In this way, the complexity is shifted from the optical and mechanical hardware to the digital software processing domain where the main limitation is computing capability.

This work was done by Glenn de Vine and Danielle M. Wuchenich of Caltech, and Daniel A. Shaddock for NASA’s Jet Propulsion Laboratory. NPO-49135

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Optical Phased Array with Digitally Enhanced Interferometry

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This article first appeared in the May, 2014 issue of NASA Tech Briefs Magazine.

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