Boulder Nonlinear Systems, Inc.

United States of America As Represented by the Secretary of the Air Force

North Carolina State University

Martin Marietta Corporation

Steven A Serati

Gary Dean Sharp

Chulwoo Oh

Douglas J McKnight

Paul Francis McManamon

Michael James Escuti

Jihwan Kim

Darren M Simon

Michael S Salisbury

Teresa Kaye Ewing

Systems, methods, and apparatus are disclosed for attenuating an incident polarized light beam using a plurality of Liquid Crystal Polarization Gratings ('LCPGs') and one or more switchable liquid crystal layers. When four LCPGs are used, a spacing between first and second LCPGs can be equal to a spacing between third and fourth LCPGs. Pi and FCL cells can also be used in place of more traditional LC switches. Switching of the LC switch can be imparted via an AC bias.

Compact liquid crystal beam steering devices including multiple polarization gratings

A beam steering apparatus includes a first beam steering stage and at least a second beam steering stage arranged in-line with the first beam steering stage. The first beam steering stage includes a first polarization grating comprising a uniaxial birefringent material having a first periodic director pattern, and the second beam steering stage includes a second polarization grating comprising a uniaxial birefringent material having a second periodic director pattern. In nonmechanical embodiments, a polarization selector may be arranged to provide a circularly polarized input beam incident on the first polarization grating. In mechanical embodiments, at least one of the first polarization grating and the second polarization grating may be operable to be independently rotated about an azimuth thereof. Related methods of operation are also discussed.

Beam steering devices including stacked liquid crystal polarization gratings and related methods of operation

The present invention provides a polarizing interferometer multiplex spectrometer using a zero-order switch, a multi-order switch and an output polarizer to multiplex the recovery of an entire input spectrum. The zero-order switch and multi-order switch require input light of a fixed polarization; thus the present invention provides a preferred embodiment that uses a zero-order switch and a multi-order switch positioned between an input polarizer and an output polarizer. For a sequence of time delays incremented by the multi-order and zero-order switches, the total transmitted power at all wavelengths is measured. From these, the coefficients of a Fourier series representation of the input spectrum are obtained, and the entire spectrum is mathematically reconstructed. Although the structure is similar to a tunable interference filter, the PIMS does not function as a filter, and more particularly, does not scan the transmission wavelength and measure power as a function of wavelength. The present invention further provides a multi-order switch that uses an active LC device to switch between summing and differencing the retardances of two fixed retarders. The present invention further provides a method of obtaining a Fourier series representation of a spectrum of input light.

Polarizing interferometer using multiorder and zero order birefringence

To greatly increase the sensitivity of a Heterodyne Ladar System, the receiver incorporates an optical preamplifier to amplify the ladar return signal prior to detection. This results in an increase in return signal power on the order of 25 dB. Spontaneous emission noise added by the fiber amplifier counters this gain in a normal scheme. The proposed receiver, however, incorporates a Polarization Optical Mixer to perform balanced mixing, thus rejecting added spontaneous emission beat noise terms and resulting in a large increase in system sensitivity.

Ladar receiver incorporating an optical amplifier and polarization

An optical correlator uses ferroelectric liquid crystal spatial light modulators (FLC-SLM's) in both the reference and filter planes. The SLM's include an electrically addressable memory to store images in the form a two-dimensional array of reflective pixels beneath the FLC layer. The SLM's selectively rotate the polarization of the light reflected by each pixel in accordance with the stored image. In particular, a laser produces a polarized beam that is directed through a first polarizing beamsplitter and onto the reference SLM. This beamsplitter blocks unmodulated light reflected by the reference SLM and transmits modulated light through a set of Fourier tranform lenses. The resulting beam is directed through a second polarizing beam splitter onto a filter SLM that has been programmed with the complex conjugate of the Fourier transform of a desired target image. Unmodulated light reflected from the filter SLM is blocked by the second polarizing beamsplitter and modulated light is reflected by the second polarizing beamsplitter through a set of inverse Fourier transform lenses. A CCD camera detects any correlation peak produced by the inverse Fourier transform lenses. A computer system downloads images to the SLM's and analyzes the correlation peaks detected by the camera. A half-wave plate can be included between both sets of SLM's and polarizing beamsplitters to allow manual adjustment of the polarization of the incident beam entering the SLM.

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Golden, CO, United States of America

Steven A Serati