Montana State University

Tiejun Chang

Kristian D Merkel

William Randall Babbitt

Krishna Rupavatharam

Zachary Cole

Mingzhen Tian

Randy Ray Reibel

Kelvin Wagner

Techniques for detecting optical spectral properties of a target are described. The technique includes providing an optical carrier which has an optical frequency bandwidth which is narrow compared to the width of the narrowest spectral feature of the target to be determined. This optical carrier is then electro-optically modulated with an RF frequency chirp, creating an optical chirp probe beam with a frequency chirped optical spectrum having upper and lower frequency chirped sidebands that have amplitudes sufficient to be detected at a detector. The sidebands are frequency bands arranged symmetrically around the optical carrier frequency. The attributes of a sideband include a start frequency, bandwidth and chirp rate. A probe beam is generated with the sidebands and directed onto a target having a physical property with optical frequency dependence. An optical response signal resulting from an interaction between the probe beam and the target is detected. The optical frequency dependence of the physical property of the target is determined based on the optical response signal and the attributes of the sidebands.

Method and apparatus for detecting optical spectral properties using optical probe beams with multiple sidebands

Techniques for reconfiguring spectral features stored in a medium based on a two-state atomic system with transition dipole moment &#x3bc; includes causing a chirp to pass into the medium. The chirp includes a monochromatic frequency that varies in time by a chirp rate &#x3ba; over a frequency band Bduring a time interval T. The amplitude Aof the chirp is constant over Band equal to=(bar/&#x3bc;&#x3c0;)&#x221a;{square root over ((&#x3ba; ln [2/&#x3b5;]))},The term hbar is reduced Plank's constant, ln is a natural logarithm function, and &#x3c0; is a ratio of a circumference of a circle to a diameter of the circle. For &#x3b5;&#x3c;&#x3c;1, the atomic-state populations in the two states are inverted. For &#x3b5;=1, prior atomic-state populations are erased, with final populations equal in the two states, regardless of populations before erasure.

Techniques for using chirped fields to reconfigure a medium that stores spectral features

Techniques for analog processing of high time-bandwidth-product (TBP) signals use a material with an inhomogeneously broadened absorption spectrum including multiple homogeneously broadened absorption lines. A first set of signals on optical carriers interact in the material during a time on the order of a phase coherence time of the homogeneously broadened absorption lines to record an analog interaction absorption spectrum. Within a time on the order of a population recovery time for a population of optical absorbers it the material, the interaction absorption spectrum in the material is read to produce a digital readout signal. The readout signal represents a temporal map of the interaction absorption spectrum, and includes frequency components that relate to a processing result of processing the first set of signals. The techniques allow processing of RADAR signals for improved range resolution to a target, as well as speed of the target, among other uses.

Method and apparatus for processing high time-bandwidth signals using a material with inhomogeneously broadened absorption spectrum

Techniques for recovering optical spectral features include receiving a detected time series that represents a temporally varying intensity of an optical signal. The optical signal is formed in response to an interaction between a target optical spectrum and a chirped optical field. The chirped optical field is an optical field that has a monochromatic frequency that varies in time. The target optical spectrum is an optical frequency dependent optical property of a material or device. A phase correction factor is determined based only on one or more properties of the chirped optical field. The detected time series is corrected based on the phase correction factor to produce an output time series that reproduces in time a shape of the target spectrum in frequency. These techniques allow for fast measurement of spectral features and eliminate the need for prior knowledge of the target optical spectrum to adjust the chirp rate.

Growing community of inventors

Bozeman, MT, United States of America

Tiejun Chang