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: 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 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: (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: In order to protect a delicate photo-detector from high-intensity optical radiation such as from a laser, a device for limiting power to the detector is interposed between the radiation and detector. This device has two embodiments and is made such that high-intensity radiation is totally reflected. In the absence of high-intensity radiation, total reflection is frustrated, and desired radiation passes to the detector. Both embodiments use two prisms with parallel surfaces skewed to incident radiation and with a slightly absorbant optical material between the surfaces. Desired radiation normally passes through the prisms and the material to the detector. In one embodiment, the material is a liquid which vaporizes in response to high-intensity radiation, and in the other embodiment, the material expands and pushes the prisms apart. In either case, transmission of radiation halts, and the radiation is totally reflected by a prism skewed surface.

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.