Adaptive Compensation of Atmospheric Turbulence in Ground-to-Ground Laser Communication Systems
Abstract
Two silicon based devices were investigated for use as an optical wave-front sensor to provide error signal inputs to an adaptive optic wave-front control system intended to reduce the effects of atmospheric turbulence in ground-to-ground laser communication systems. One device was an active sensor array fabricated in CMOS. The other was a silicon photoconductive optical detector with surface electrodes expected to produce PEMF photocurrents in response to spatial motion of an optical interference pattern that illuminates the region between the surface electrodes. Instead, the predominant photo-response mechanism in silicon was found to be due to the Dember effect, namely photocurrents that flow through the device in short circuit configuration that arise from photoexcited charge carrier concentration gradients formed between the illuminated regions of the semiconductor and the dark, shadowed region directly below the surface metal contact electrodes. The Dember photocurrents depend in a complicated way on fringe position relative to the contact electrodes, fringe spacing, and temporal frequency of sinusoidal phase modulation impressed on one beam. The Dember photo-response characteristics of this type of photodetector were mathematically characterized and experimentally verified for the first time, to the best of our knowledge, by the work performed under this award.
Document Details
- Document Type
- Technical Report
- Publication Date
- Dec 01, 2003
- Accession Number
- ADA419179
Entities
People
- Frederic M. Davidson
Organizations
- Johns Hopkins University