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: Production of F.sub.2.sup.+ color centers in alkali halide crystals with densities high enough for efficient use in lasers is achieved by a two-step, highly selective photoionization mechanism. This mechanism is coupled with the use of suitable divalent metal ions as efficient and stable electron traps to allow nearly 100 percent conversion of F.sub.2 color centers to F.sub.2.sup.+ color centers. The two-step photoionization mechanism comprises photo-exciting the F.sub.2 color center to the first bound state, which requires lower energy than the corresponding transition for F color centers, then photoionizing the F.sub.2 color center from the first bound state, and finally, capturing the electron thus liberated on the divalent metal ions.

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: An improved method of forming ternary and quaternary epitaxial films by molecular beam epitaxy involves controlling precisely the ratio of concentrations of two alloying elements in the final compound by heating predetermined independently adjustable quantities of two or more alloying elements in the same oven.

Abstract: Acoustical and optical surface wave filters are described wherein the filter characteristic near resonance is provided by cascaded grating resonators. The out-of-band suppression for these resonators is provided by a track changing element that includes a four-port directional coupler having one port connected to receive input energy and a fourth port connected to couple energy into the cascaded grating resonators. Tapered and chirped reflection gratings are positioned so as to selectively reflect energy present at the second and third ports of the directional coupler. In a surface acoustic wave embodiment of the invention, the directional coupler is provided by a multistrip coupler. In an optical embodiment, the directional coupler function is provided by waveguiding structures that are brought sufficiently close to induce 3 dB coupling.

Abstract: A wavelength division optical multiplexer for combining single mode beams involves a lens formed in a thin-film waveguide and a reflection diffraction grating outside the waveguide.

Abstract: A light-activated light-emitting device has at least one p-n junction provided with electrodes for confining light-emission to an area of the junction. It has been determined that light-emission can be activated by light impinging on the junction outside this confined area, so two optical fibers are provided, one being an input fiber for bringing activating light to the nonemitting sensitive part of the junction and the other fiber being an output fiber coupled to the light-emitting area. When the device is a p-n-p-n light-activated light-emitting switch provided with an RCL reset control circuit, a very inexpensive unidirectional optical pulse regenerator is obtained. The device in its various forms is advantageously suited for use in each of many stations along optical fiber data busses or in optical logic arrays because the unidirectional feature prevents light feedback between adjacent devices and consequently avoids spurious switching of a preceding device.

Abstract: An integrated optical filter composed of coupled nonidentical strip waveguides in LiNbO.sub.3 is disclosed. The device has a broad bandwidth, is tunable over several hundred angstroms, and offers electrical control of the crossover efficiency. Several devices are combined on a single substrate to provide an electrically tunable multiplexer or demultiplexer.

Abstract: An apparatus is disclosed for making unchirped holographic diffraction gratings that are formed from curved lines in a thin film. The gratings so made focus as well as reflect light that is confined to the film incorporating the grating. SUBACKGROUND OF THE INVENTIONGratings have been incorporated in integrated optics devices for several purposes, including the fabrication of distributed feedback lasers, light-wave couplers, and band-rejection filters. Integrated-optics gratings known to the prior art were composed at straight lines, and therefore could not focus the light being processed. Gratings that combine focusing and diffraction were known to be desirable, but the prior art was unable to produce them.The closest prior art that has come to our attention is a method and apparatus for producing curved-line holographic gratings that have unequally spaced, or chirped, lines (U.S. Pat. No. 3,578,845, issued on May 18, 1971 to K. E. Brooks et al).

Abstract: A method of epitaxial crystal growth is disclosed in which the lattice constants of adjacent layers are in the ratios of small integers other than one. This method permits the use of previously incompatible compounds, in particular the combination of magneto optic and electro optic elements on the same substrate.

Abstract: A tunable far infrared generator makes use of a four-photon mixing process that cycles among highly excited atomic states, the lowest of which states is reached from the atomic ground state by a visible or ultraviolet photon, and the remainder of which states are connected by transitions in the infrared.

Abstract: An optical fiber coupling assembly is mounted on the back of a repeater module so that when the repeater is slid into a rack near which an optical fiber frame plug is mounted, the optical fibers of the frame plug are laterally captured at an orientation angle by tapered grooves in an alignment receptacle of the coupling assembly and progressively urged so as to be precisely positioned near repeater optical fibers or semiconductor devices. A spring loaded construction automatically decreases the orientation angle to zero so that the fibers rest in the whole length of the grooves. The assembly additionally slides the fibers relative to the grooves and into abutment with the fibers or devices to which they are being coupled.

Abstract: A multiplexer/demultiplexer for optical fibers is disclosed that features a reflection diffraction grating and a graded refractive index rod in a rugged, compact assembly having low insertion loss and low crosstalk.

Abstract: An optical fiber waveguide is disclosed wherein germanium dioxide (GeO.sub.2) and phosphorus pentoxide (P.sub.2 O.sub.5) are radially graded in the core of the optical fiber for the purpose of achieving minimum modal dispersion over a broad range of wavelengths. The phosphorus pentoxide has its maximum concentration on the axis of the fiber core and is graded to zero concentration at the core-cladding interface. The germanium dioxide has its maximum concentration at the core-cladding interface, is constant throughout the cladding and is graded to zero concentration on the axis of the fiber core. The ratio of maximum P.sub.2 O.sub.5 to maximum GeO.sub.2 is approximately 11.6 and therefore the numerical aperture is only slightly degraded as a result of the reverse doping of germanium dioxide.

Abstract: An optical fiber waveguide is disclosed wherein the cladding surrounds a fiber core having a noncircularly symmetric cross section. Equations are presented which dictate the value of the index of refraction that must be provided at each spatial point within the fiber core in order to construct a fiber waveguide having minimum modal dispersion. An especially useful optical fiber waveguide is disclosed with an elliptical fiber core thereby providing a fiber which can be more efficiently coupled to a light emitting source having an elongated source area such as in a heterojunction laser or an edge-emitting light emitting diode.

Abstract: An optical fiber having three dopants in the core of the fiber and a pure silicon dioxide cladding is disclosed. Phosphorus pentoxide and germanium dioxide are radially graded in the core of an optical fiber to obtain minimum modal dispersion over a broad range of wavelengths. A uniform concentration of boron oxide is present throughout the core of the fiber in order to permit a pure silicon dioxide cladding without encountering any step discontinuity in the index of refraction at the core-cladding interface.

Abstract: A method of fabricating an optical fiber connector is disclosed using a transfer molding process employing a precision die whose interior surface defines a frustum for forming the mating surface of the connector. The fiber is inserted through the mold cavity and extends through an aperture in the end surface of the frustum and through an annulus disposed outside of the mold cavity immediately adjacent to the aperture. At the transfer molding temperature, the annulus expands inward radially, simultaneously sealing the aperture and centering the fiber. After curing, the excess fiber is removed, and a flexible, dome-shaped contacting member is formed over the fiber end.

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.