Abstract: A power limiter is provided consisting of two cells of optically transparent material having a low index of refraction, but a large third order susceptibility to electric polarization. The input cell has a positive susceptibility which self-focuses intense radiation beams (i.e., laser beams) and the output cell has a negative susceptibility which scatters the even more intense self-focused beam by self-defocussing.

Abstract: An optical material having an index of refraction related to wavelength is placed between the reflectors of a Fabry-Perot cavity employed as an interference filter. The cavity is skewed with respect to the optical path of incident radiation such that the material diverts the optical paths of different spectral lines and the filter response more nearly matches the line spectrum.

Abstract: An optical material having an index of refraction dependent on wavelength of incident radiation is used between the reflectors of an off-normal Fabry-Perot cavity used as an interference filter. External to the cavity, and in the direction of incident radiation, another optical material having an index of refraction dependent on wavelength of radiation is placed. The incident radiation is thus refracted into and within the cavity dependent on its wavelength. By proper choice of the indices of refraction, and other variables, the filter may be designed to exactly match the output spectrum of a line spectrum laser, and to transmit all spectral lines of the laser, but to reflect all other radiation of interest.

Abstract: A filter is constructed consisting of an optical cavity having at least one element which is a square mesh of highly-conductive metal on a transparent substrate. The mesh openings are defined by relatively narrow conductors of the metal. The mesh feature size, as determined by the sum of the conductor width and square size length, is below the diffraction limit for incoming radiation of interest.

Abstract: Incident radiation is focussed by a lens into a non-linear optical material whose index of refraction increases with increased radiation intensity. For normal radiation, the radiation freely passes through the nonlinear optical and an optically-switchable material to an other lens. This other lens directs the radiation onto a photodetector. High-intensity radiation, however, is self-trapped in the nonlinear material to form a columnar beam which falls on the optically-switchable material, causes this material to switch, and is reflected thereby.

Abstract: A trilaminar semiconductor device is placed at an intermediate focus is an optical instrument having a sensitive photodetector. The layers of the device are successively in the form of a two-photon absorber, a sacrificial layer, and a multiple quantum well. The composition of the semiconductor is varied in the layers to achieve the desired bandgap and function.

Abstract: In order to protect a delicate photodetector from high-intensity radiation, such as from a laser, a device for limiting optical power to the detector is interposed between the radiation and the detector. This device has an optical interface that totally reflects high-intensity radiation, but which freely transmits normal (low intensity) radiation to the detector. The interface is between two optical materials, one with a linear index of refraction with respect to radiation intensity, and the other with a non-linear index. At low intensity radiation levels, the two materials have the same indices of refraction, and such radiation is freely transmitted through the interface, but with high-intensity radiation, a mismatch of indices of refraction allows total reflection at the interface.

Abstract: A passive broadband sensor protection and enhancement system and technique. ncident light is focused with a cylindrical lens on the optical axis into an intense light strip onto the input face of a photorefractive crystal which may include optional anti-reflection coatings on the input and output face. A broadband high reflection coating proximate to the input face reflects all radiation from approximately 0.68 out to at least 1.5 micrometers wavelength and light exiting includes a transmitted beam and beam fan. A weak holographic grating is used to seed the beam fan, such that is fanned out of the optical path in a direction determined by the c-axis, dominant electro-optic coefficient, and charge carriers participating in the photorefractive process. The transmitted beam contains only incoherent radiation as input to a sensitive detector resulting in broadband multiline protection from the visible spectrum for substantially all pulsewidths and cw lasers, with enhanced time response and interaction length.

Abstract: A passive broadband sensor protection and enhancement system and technique. ncident light is focused with a cylindrical lens on the optical axis into an intense light strip onto the input face of a photorefractive crystal on the optical axis. The crystal includes optional anti-reflection coatings proximate to the input and output face. A broadband high reflection coating is proximate to the input face for reflection of all radiation from approximately 0.68 to at least out to 1.5 micrometers wavelength. Light exiting from the output face of the crystal results from a photorefractive process that includes a transmitted beam and beam fan. The beam fan is fanned out of the optical path in a direction determined by the c-axis, dominant electro-optic coefficient, and charge carriers participating in the photorefractive process.

Abstract: A liquid crystal modified by the addition of an organic dye is used as a non-linear optical material in two devices which limit the optical radiations to sensitive photodetectors.

Abstract: A universal IFF technique and system utilizes a real-time communication l established between both parties allowing the approximate immediate transferral of digital information with positive direction and identification of both parties achieved. A pump laser emits a first signal at a first position and a remote laser beacon emits a second signal at a second position, both signals at nominally the same wavelength. A MPPCM receives the first signal which establishes a beam fan. The MPPCM and first signal scans about a region of interest to intercept the second signal. The second signal provides a second input signal into the MPPCM so that a two-way phase conjugation signal builds up and lock-on is established.

Abstract: (S) A first optical material with a linear index of refraction is distributed as particles in a second optical material with an index of refraction dependent on the incident radiation intensity. Below some threshold intensity level the combination of materials is transparent to incident radiation directed toward a sensitive optical detector. Above this level, high-intensity incident radiation induces a change in refractive index of the second material, and the combination is limiting to incident radiation.

Abstract: The present invention provides layered polymeric media to control the spatial and spectral distribution of energy in optical beams, particularly high intensity, broadband, multi-line laser beams. This structure is an improved version of prior art thin-film (vaccum deposited) interference filters and "rugate" structure filters.

Abstract: This is a new use for known photorefractive crystals. If input radiation taining both non-coherent and multiple-line coherent radiation is directed into such a crystal from a predetermined range of directions with respect to the C axis of the crystal, rainbow scattering of the coherent radiation occurs, whereas normal scattering of the non-coherent radiation occurs. A detector toward which input radiation is directed through the crystal is thus protected from high-power, multiple-line coherent radiation such as that provided by a threat laser.

Abstract: Non-linear optical materials, i.e., those optical materials whose indices refraction depend on input radiation intensity, are few and of low non-linearities; this invention uses various metallic patterns on a transparent substrate, with non-linear elements between parts of the patterns, to function as an artificial dielectric. These elements may take the form of metal-oxide-metal tunnel diodes, Schottky diodes, p-n junction diodes, superlattice structures, and non-linear capacitors.

Abstract: The present invention provides layered polymeric devices to control the sial and spectral distribution of energy in optical beams, particularly high-intensity laser beams. These devices include improved versions of prior art thin-film (vacuum-deposited) interference filters, rugate structure anti-reflection coatings, Q-switches, pulse shapers, modulators, optical bistable devices and the like.

Abstract: The present invention provides layered devices to control the spatial and spectral distribution of energy in optical beams, particularly high-intensity laser beams. These devices include improved versions of prior art thin-film (vacuum-deposited) interference filters, rugate structure anti-reflection coatings, Q-switches, pulse shapers, modulators, optical bistable devices and the like. Control is provided using materials with large second and third order susceptibilities to electric field polarization and, if necessary, means to apply appropriate electric fields.

Abstract: A metallic pattern is applied to a dielectric substrate to form the inventive device. The pattern is a mesh or array of islands with two-fold symmetry, i.e., bisymmetrical but with unequal orthogonal dimensions. Lamination of the devices may be formed to make various types of waveplates and filters.