In a one-dimensional liquid crystal optical phased array
(LCOPA), a liquid crystal layer is electrically addressed by an
array of long, narrow electrodes. A spatially periodic voltage
profile can be applied to the liquid crystals in order to induce a
sawtooth-shaped index of refraction variation in the liquid
crystal layer that will steer an optical beam in a fashion
analogous to that of a blazed diffraction grating. In reality, an
LCOPA is a thick, periodic, anisotropic structure with complicated
polarization properties. The changes in polarization as a beam
passes through an LCOPA can have negative practical effects,
particularly in optical systems where LCOPAs and other
polarization-sensitive optical elements are cascaded. This paper
presents experimental measurements of the polarization state of
the light diffracted by an LCOPA as well as a discussion of the
origin of these effects.
In a one-dimensional liquid crystal optical phased array (LCOPA), a liquid crystal layer is electrically addressed by an array of long, narrow electrodes. A spatially periodic voltage profile can be applied to the electrodes in order to induce a sawtooth-shaped index of refraction variation in the liquid crystal layer that will steer an optical beam in a fashion analogous to that of a blazed diffraction grating. Because of non-ideal device behavior, measured phase vs. voltage data cannot be used to predict the control voltages necessary to achieve efficient steering. This paper presents a simple application of optimization to determine the appropriate voltages for every electrode in order to optimize the steering efficiency. Experimental results show that this approach can quickly determine optimal voltages for a desired far field diffraction pattern. Steering efficiency improvements of over 100 percent are obtained as compared to open loop device calibration.
Here we investigate a novel approach to steering broadband imagery with a Liquid Crystal Optical Phased Array (LCOPA). Our approach overcomes the deleterious blurring and echoing effects inherent in the use of such a device. We develop a model for the LCOPA and formulate a method in which a steered, graybody scene may be restored through the application of a Wiener filter. We also show this approach may be extended to scenes that are not strictly composed of graybodies but instead are only spectrally smooth over an appropriate bandwidth. Experimental results are presented that demonstrate the effectiveness of this approach.
Optical Phased Array technology promises to reduce the
size, weight, and power consumption of optical pointing and
steering systems by replacing complex mechanically gimballed
mirrors with small, lightweight, nonmechanical devices. This paper
develops and describes several diagnostic techniques that can be
used to evaluate the performance of Optical Phased Arrays (OPAs)
and demonstrates their use by applying them to the evaluation of a
commercially available liquid crystal device. Finally, the
operation of this device is demonstrated by integrating it into a
steered imaging system.