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Proceedings Paper

Characterization of a multilayered dielectric transmissive phase modulator
Author(s): Andrew S. Keys; Richard Lynn Fork; Thomas R. Nelson Jr.; James E. Ehret; Joseph E. Van Nostrand
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Paper Abstract

We describe a multilayered dielectric stack configuration designed specifically for use as a transmissive phase modulator for broadband optical signals. Applications for this device range from full aperture wavefront correction to nonmechanical beam steering arrays for free space optical communication links. Our implementation employs alternating GaAs and AlAs layers of varying thickness on a GaAs substrate to create a bandpass region of high average transmission in the near infrared. Within this transmission bandpass, the phase component of the complex transmission coefficient varies in a near-linear fashion with respect to wavelength. The transmission bandpass is designed to have a bandwidth of 21.0 nm (or 6.3THz frequency bandwidth) and to have an edge-to-edge relative phase change of greater than 4p radians. Modification of the stack materials' optical properties causes the transmission profile to shift spectrally, resulting in a phase modulation for specific bands of transmitted frequencies. Our broadband phase modulator imparts nearly a full-cycle of phase modulation with low loss and low group velocity dispersion. A sample comprising 91 alternating layers has been fabricated to exhibit the bandpass properties required for optical signal phase modulation. We experimentally characterize the sample using an interferometer and spectrometer to measure the spectral transmission and relative phase profiles and to assess the relative phase modulation in response to a variable angle of incidence. We compare the experimental data to computational predictions and discuss the results.

Paper Details

Date Published: 26 December 2001
PDF: 12 pages
Proc. SPIE 4438, Physics, Theory, and Applications of Periodic Structures in Optics, (26 December 2001); doi: 10.1117/12.451482
Show Author Affiliations
Andrew S. Keys, NASA Marshall Space Flight Ctr. (United States)
Richard Lynn Fork, Univ. of Alabama in Huntsville (United States)
Thomas R. Nelson Jr., Air Force Research Lab. (United States)
James E. Ehret, Air Force Research Lab. (United States)
Joseph E. Van Nostrand, Air Force Research Lab. (United States)

Published in SPIE Proceedings Vol. 4438:
Physics, Theory, and Applications of Periodic Structures in Optics
Philippe Lalanne, Editor(s)

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