So-called "free-space" laser communication systems working near the surface of the Earth must operate in the
presence of atmospheric turbulence. The effects of the atmospheric turbulence on the laser beam which are
relevant to optical communications are a broadening of the laser footprint, random jitter of the laser beam, and
high spatial frequency intensity fluctuations referred to as scintillation. The overall goal of our program is to
improve performance and extend the range of optical communications systems by exploring the use of adaptive
optics and channel coding. To better model the performance of a real system operating in the real world, we have
developed an outdoor turbulence-measurement and monitoring system. In this paper we describe an atmospheric
turbulence monitoring system for three kilometers, partially over water path. The laser transmitter operates
at 808 nm with a source power of 2mW. The receiver consists of relay optics, a Hartmann wave front sensor
(WFS), and a CCD camera. The WFS is used to monitor atmospheric turbulence-induced phase aberrations,
and the camera is used for both conventional imaging studies and measurements of anisoplanatic effects. In this
paper we describe this system and present some preliminary results obtained from the measurements.
The IR antenna-pair coupled micro-bolometers has demonstrated its unique power response features compared to the single antenna coupled micro-bolometers. The response pattern is determined by that of the single antenna and an interference oscillation term of the antenna-pair with respective to the angle of incidence of the radiation field, and can be steered by shifting the location of the bolometer. This paper explores the potential application of antenna-pair coupled detector in beam synthesis. It describes an array configuration based upon these micro-bolometers, and discusses the corresponding coherent data processing method for the purpose of obtaining response pattern narrowing effects from such an array. This directional gain enhancement, together with the beam steering control, could potentially lead to an array capable of providing a novel IR lensless imaging technique.
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