Abstract: An optical pulse shaping device and methhod of shaping an optical pulse involves the use of a phase coherent multi-frequency light beam with an optical element consisting of a sample containing an absorption band with multiple holes. The holes are burned into the sample to selected depths at selected frequency locations, thereby permitting the relative phases and amplitudes of the input frequency components of the beam to be independently varied to arbitrary values. This system enables a generalized Fourier synthesis of optical pulses such as a laser with designed temporal profiles to be effected.

Abstract: A method and device for detecting a narrow spectral feature in a sample is described. The method includes the steps of providing a beam of light having an optical frequency bandwidth which is narrow compared to the width of the narrow spectral feature and having a center frequency .omega..sub.C which lies near the narrow spectral feature, phase modulating the beam of light with a single RF frequency to provide a pure FM spectrum having upper and lower sidebands, exposing the sample containing the narrow spectral feature to the modulated light so that only one of the FM sidebands probes the narrow spectral feature, photodetecting the light emerging from the sample to detect a RF beat at the specific RF frequency used for phase modulation, and electronically monitoring the amplitude of the RF beat signal to indicate the strength of the narrow spectral feature. A preferred embodiment of this invention is a multiplex readout device for hole burning memories.

Abstract: A wide angular aperture, tunable filter device is achieved by using degenerate four-wave mixing. The apparatus utilizes two counter-propagating pump beams at substantially the same frequency to interact with an object beam, containing a spread of frequency components through a third order nonlinearity in the susceptibility of a medium. This produces a conjugate image beam formed with frequency components close to the frequency of the pump beams. By tuning the frequency of the pump beams the object beam frequency spectrum may be scanned while preserving all of the spatial information in the object beam. Apparatus for generating velocity contours of moving objects is also disclosed.

Abstract: An apparatus is disclosed for servo-locking the angular orientation of a nonlinear crystal to the angle at which phasematching occurs for nonlinear optical frequency mixing processes. Two secondary beams are generated from a beam of radiation which is incident upon the crystal. They travel through the crystal at small angles with respect to the main beam and each generates a secondary output beam containing new frequency components produced by the nonlinear optical frequency mixing process in the crystal. A discrimination signal is created by subtracting the generated power at the new frequency component of one of the secondary output beams from the generated power of the other. This signal is sensitive to the angular misalignment of the crystal and is used to drive a servo system to maintain the proper angular orientation for phasematching.

Abstract: A high speed, wide angular aperture, spectrally selective optical gate is achieved by using degenerate four-wave mixing. The apparatus utilizes two counterpropagating pump beams to interact with a probe beam through a third order nonlinearity in the susceptibility of a medium to produce an image beam which is counterdirectional to the probe beam. The image beam is produced only during the time that the two pump beams and the probe beam are coincident in time and space in media having a fast nonlinearity. In slow media, fast gating is achieved by turning off both pump beams after the probe beam and the pump beams have interacted. This apparatus produces gate times which are not limited by the speed of relaxation of the nonlinearity in the medium utilized.

Abstract: Atoms of hydrogen or deuterium are fully ionized by a three-photon process which is enhanced by the two-photon 1S.fwdarw.2S resonant transition. The resultant ions are detected with high efficiency to provide discrimination between small concentrations of atomic hydrogen and atomic deuterium in a vacuum or in the presence of a background gas. The use of two unequal photo energies to pump the two-photon resonance provides the capability of mapping the individual three dimensional distribution of the hydrogen or deuterium. The detection process is also appropriate to determining these data in dishcarge plasmas and flames.

Abstract: A switchable diffraction grating may be formed from an array of color centers in an alkali halide crystal. These gratings will diffract only when the color centers are excited by an external light source, so that they may be switched on and off. The gratings may be used to form optical switches, pulse shaping devices, and Q-switched lasers.

Abstract: The invention relates to an ellipsometer for measuring the degree of elliptical polarization of a beam of coherent optical radiation. Applications of the invention include a device for measuring birefringence and a material detector for measuring small concentrations of substances in a gaseous medium.