
Proceedings Paper
An investigation of stair mode in optical phased arrays using tiled aperturesFormat | Member Price | Non-Member Price |
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Paper Abstract
With an optical phased array, the individual phases of a multi-fiber laser source can be manipulated by exploiting high-bandwidth
phase loops to correct for aero-optical flow over the turret and free-stream atmospheric effects along the line
of sight; however, rough surface scatter through laser-target interaction adds the additional constraints of speckle and
depolarizing effects. In particular, speckle phenomena can cause unobservable modes to arise in the beam control
system of optical phased arrays. One such unobservable mode is termed stair mode and is appropriately identified by a
stair-step pattern of piston phase across the individual subapertures that comprise a tiled aperture. This paper
investigates the effects of stair mode using wave-optics simulations. To represent different array fill factors in the source
plane, both seven and 19 element hexagonal close-packed tiled apertures are used in the simulations along with both
Gaussian and flat-top outgoing beamlets. Peak Strehl ratio and power in the bucket are calculated in the target plane for
all simulation setups and are then averaged for multiple random realizations of stair mode step sizes. In addition, the
stair mode target irradiance patterns are imaged with cameras which have decreasing aperture stop diameters. Initial
results show that low resolution imaging conditions, i.e. an aperture stop on the order of a subaperture diameter, makes it
difficult to distinguish between different realizations of stair mode using a separate camera sensor.
Paper Details
Date Published: 15 October 2012
PDF: 15 pages
Proc. SPIE 8520, Unconventional Imaging and Wavefront Sensing 2012, 852006 (15 October 2012); doi: 10.1117/12.942634
Published in SPIE Proceedings Vol. 8520:
Unconventional Imaging and Wavefront Sensing 2012
Jean J. Dolne; Thomas J. Karr; Victor L. Gamiz, Editor(s)
PDF: 15 pages
Proc. SPIE 8520, Unconventional Imaging and Wavefront Sensing 2012, 852006 (15 October 2012); doi: 10.1117/12.942634
Show Author Affiliations
Mark F. Spencer, Air Force Institute of Technology (United States)
Milo W. Hyde IV, Air Force Institute of Technology (United States)
Published in SPIE Proceedings Vol. 8520:
Unconventional Imaging and Wavefront Sensing 2012
Jean J. Dolne; Thomas J. Karr; Victor L. Gamiz, Editor(s)
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