Abstract: Techniques for producing an optical broadband frequency sweep or chirp, include generating a narrowband frequency chirp and a frequency-shifted replica. The narrowband chirp has an optical carrier frequency, a pulse duration and a pulse bandwidth. A frequency-shifted replica is generated by frequency shifting the narrowband chirp by a frequency shift. Adding the frequency-shifted replica after a start of the narrowband chirp by a delay generates a broadband frequency chirp. Alternatively, the frequency-shifted replica is generated by frequency shifting a constant frequency pulse, and modulating the frequency-shifted pulse to generate narrowband chirps that are added to form the broadband chirp.

Abstract: Techniques for reconfiguring spectral features stored in a medium based on a two-state atomic system with transition dipole moment ? includes causing a chirp to pass into the medium. The chirp includes a monochromatic frequency that varies in time by a chirp rate ? over a frequency band BR during a time interval TR. The amplitude AR of the chirp is constant over BR and equal to AR=(hbar/??)?{square root over ((? ln [2/?]))}, The term hbar is reduced Plank's constant, ln is a natural logarithm function, and ? is a ratio of a circumference of a circle to a diameter of the circle. For ?<<1, the atomic-state populations in the two states are inverted. For ?=1, prior atomic-state populations are erased, with final populations equal in the two states, regardless of populations before erasure.

Abstract: A method and apparatus for converting an analog waveform to a series of digital values includes receiving an input analog waveform to be digitized over a particular frequency band. A phase-sensitive frequency-domain representation of the input analog waveform is recorded. The phase-sensitive frequency-domain representation is read out and digitized to produce a spectral series of digital values. An output series of digital values that represent the analog waveform digitized over the particular frequency band is determined based on the spectral series. In some embodiments, the spectral series of digital values is produced with a conventional high dynamic range, low bandwidth digitizer that has a bandwidth at least a factor of two less than a width of the particular frequency band for digitizing the target analog waveform.

Abstract: 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.

Abstract: 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.

Abstract: Techniques for reading the spectral content of a spatial-spectral grating in an inhomogeneously broadened transition (IBT) material include directing multiple probe waveforms to probe a spatial mode of the IBT material. Each probe waveform is a linear frequency modulated chirp; each probe waveform partially overlaps in frequency with a different probe waveform; and multiple output signals are detected from the IBT material in response. Based on the multiple output signals, a readout signal is determined that represents a complete or nearly complete temporal map of the spectral content of the spatial-spectral grating. Calibration of the frequency content can be achieved by simultaneously reading out calibration spectral features. These techniques allow high-bandwidth spectral content to be read with segmented narrow bandwidth chirp probe waveforms and low-bandwidth high-dynamic-range detectors and digitizers.

Abstract: 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.

Abstract: Techniques for producing an optical broadband frequency sweep or chirp, include generating a narrowband frequency chirp and a frequency-shifted replica. The narrowband chirp has an optical carrier frequency, a pulse duration and a pulse bandwidth. A frequency-shifted replica is generated by frequency shifting the narrowband chirp by a frequency shift. Adding the frequency-shifted replica after a start of the narrowband chirp by a delay generates a broadband frequency chirp. Alternatively, the frequency-shifted replica is generated by frequency shifting a constant frequency pulse, and modulating the frequency-shifted pulse to generate narrowband chirps that are added to form the broadband chirp.

Abstract: 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.

Abstract: 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.

Abstract: Techniques for reading the spectral content of a spatial-spectral grating in an inhomogeneously broadened transition (IBT) material include directing multiple probe waveforms to probe a spatial mode of the IBT material. Each probe waveform is a linear frequency modulated chirp; each probe waveform partially overlaps in frequency with a different probe waveform; and multiple output signals are detected from the IBT material in response. Based on the multiple output signals, a readout signal is determined that represents a complete or nearly complete temporal map of the spectral content of the spatial-spectral grating. Calibration of the frequency content can be achieved by simultaneously reading out calibration spectral features. These techniques allow high-bandwidth spectral content to be read with segmented narrow bandwidth chirp probe waveforms and low-bandwidth high-dynamic-range detectors and digitizers.

Abstract: Techniques for continuously programming a coherent transient spatial-spectral optical signal processor involve the repeated application of two or more spatially distinct optical programming pulses to a non-persistent hole-burning material to write an accumulated, spatial-spectral population grating with low intensity optical pulses as compared to single shot programming. An optical data stream is introduced on a processing beam, resulting in a processor output signal spatially distinct from all the processing pulses. Programming and processing take place simultaneously, asynchronously and continuously. For accumulated gratings, the frequency stability of the optical source is an important consideration.