Abstract: A level sensor for measurement of the level of molten metal in an electron beam evaporator which operates to sense directly the position of the point or line source of evaporant by detection of radiation such as light emitted therefrom. Compensation is provided for variations in electron beam deflecting magnetic field to avoid interpreting lateral movement of the point or line source from field variations as level changes. Compensation is also provided in the detection circuit for variations in detected light intensity that would otherwise provide an erroneous indication of level change. Detection of further conditions that produce unreliable level sensing and system inhibition in response thereto is provided as a safety feature.

Abstract: A hybrid laser resonator for use with a transverse flow waveguide laser includes cylindrical optical elements for coupling together regions of a thin slab-shaped laser medium operating in the waveguide mode through a set of reflectors which define the ends of the laser cavity. Separate waveguide cylindrical optics which focus in the thin dimension of the slab are combined with a negative cylindrical lens which diverges in the thick dimension of the slab. The negative lens causes an unstable resonator condition to exist in the thick or fluid flow direction so as to prevent narrow isolated horizontal lasing bands and thus provide a nearly diffraction limited beam quality in both thick and thin dimensions.

Abstract: Apparatus and process for isotopically selective multi-step photoionization in which the final or ionizing step is tuned to produce a specific transition to an excited state above ionization for which the ionization cross-section is substantially greater than for ionization transitions in general. The autoionization transition to an ionized state is typically made from a highly excited bound state which is reached in one or two isotopically selective energy jumps from the ground state or other low-lying levels. The isotope shift for the ionization transition is typically small compared to the bandwidth of the ionization transition and relatively broad band photoionization radiation covering the entire absorption line can be employed. Broad band radiation is more economic and is preferable for use wherever possible. A technique is also shown for identifying the ionization transitions of augmented cross-section.

Abstract: A single element interposed in a laser resonator cavity provides for AM mode-locking, Q-switching and dumping in a sequential operation in which a Pockels cell or like polarization rotation device is first energized to prevent build-up of radiation in a laser cavity, is then switched to provide for mode-locking by energization with a periodically varying signal, and is finally energized to dump a single mode-locked pulse. The sequential operation permits the use of a single electro-optic element and a single pair of electrodes. Q-switching, mode-locking and dumping are accomplished utilizing the same physical effect in the crystal, e.g., polarization rotation.

Abstract: A dye solution reservoir system for a dye laser comprises a dye solution reservoir, main fluid circuit means for circulating dye solution between the reservoir and a dye laser, and a by-pass dye replenishment loop between the reservoir and the laser for (1) diverting a portion of the solution from the main circuit, (2) filtering substantially all solute, including the dye and other particles from that portion of the solution, (3) replenishing the solution by adding fresh dye solute, and (4) returning the replenished solution to the main circuit. In a preferred embodiment, the solution is filtered by a first filter for removing the dye solute and a second filter for removing degradation by-products and particulate matter. Reverse osmosis may be advantageously used as a part of this filtrate system. The advantage of such systems is a substantial reduction in the required reservoir capacity and enhanced dye recoverability.

Abstract: Method and apparatus for inducing isotopically selective photoexcitation of atoms in at least first and second energy steps. The total energy change accomplished by the two energy steps is provided with isotopic selectivity at precise resonance for the two steps. In an isotope separation system in which an environment of particles of plural isotope types is created, isotopically selective photoexcitation from laser radiation is shown to produce a great improvement in excitation efficiency where the radiation is controlled in the aggregate of plural photons to achieve precise resonance over the plurality of the degenerate energy steps. Even with multimode excitation, precise resonance is only achieved for isolated atoms, and a chirp or frequency sweep is applied to one of several excitation frequencies to insure precise resonance at least once for each atom.

Abstract: A coaxial flashlamp for pulsed operation at high repetition rates having an annular, light emitting discharge path between fluid cooled coaxially disposed, inner and outer optically transparent tubes. Electrodes are provided at opposite ends of the discharge paths and a gas such as Xenon is provided between the electrodes. The gas is discharged by confinement between the two tubes, forced to assume a dispersed shape which permits more efficient cooling at the discharge borders by fluid coolant inside the inner tube and around the outer tube.

Abstract: A system for generating pulses of laser radiation which vary in frequency with time to achieve a chirp or frequency sweep in which single or multiple laser spectra in the form of mode lines are displaced or shifted in frequency during the generation of the laser pulse. The system provides for the mode line shift through the use of an optical wedge which moves tranversely through one of the optical paths utilized in the optical loop to generate the laser pulse. This provides a linear increase with time in the optical path length so as to perturb the wavelength of oscillation of the laser output, which results in a linear chirp. In a preferred embodiment a number of prisms of optically dense material with a wedge-like profile are mounted on a rotating disc. When the disc with the prisms is interposed in the optical loop of an injection locked laser oscillator, successive prisms traverse the laser's optical loop.

Abstract: A single electro-optic device is provided for simultaneously mode-locking and chirping the output of a laser by simultaneously applying to the electrodes of the electro-optic device a periodic signal superimposed on a voltage ramp. The electro-optic device in general utilizes a crystal of the type which changes refractive index in accordance with an applied voltage. As a result, FM mode-locking is achieved through the use of the periodic signal, whereas mode lines are displaced or shifted in frequency during the generation of the laser output by virtue of the changing bias supplied by the voltage ramp.

Abstract: A tubular valve for controlling the flow of fluids includes an outer tubular shell having pairs of ports on diametrically opposed surfaces and an inner coaxial transfer tube having pairs of openings which are selectively rotated into or out of alignment with the outer tubular ports. Deformable grommets enclose and seal the space between the outer shell and inner tube and provide lateral tubular extensions projecting through the outer ports for connection to external sources and apparatus. The inner transfer tube, which is rotatable within the grommets, provides communication for fluid flow between inlet and outlet ports and openings. Different fluids may be selectively controlled and supplied through separate outlets.During assembly, each deformable grommet is folded around an insertion device which is inserted into the outer tubular shell and twisted to release the tubular extension which projects laterally from the port.

Abstract: A fluid laser having a flow channel between fluid inlet and active lasing regions and in which medium heating and resulting medium disturbances are reduced by minimizing channel wall and window heating in the area of the channel bordering the window seal. The channel wall includes a bevelled portion exterior of the channel and having a highly reflective surface immediately adjacent a window. The resulting thinning of the channel wall immediately adjacent the window reduces the absorption in the window seal region of reflected flashlamp light and of dye fluorescence light originating from within the flow channel, and the highly reflective surface reflects away from the window seal region the dye fluorescent light and reflected lamp light. Polished edge surfaces on the window also refract away from the window seal region the dye fluorescent light and reflected light passing through the window/air interface.

Abstract: The problems of collimating, synchronizing and combining a plurality of laser beams to generate a composite beam are substantially reduced by the use of one or more lasers especially adapted to lase in two or more separate wavelengths. Specifically, a composite beam generating system comprises at least one multiwavelength laser for emitting a multiwavelength beam having at least two separated wavelength components, one or more additional lasers for generating respective additional beams, and means for combining the multiwavelength beam with one or more additional beams. In a preferred embodiment, a four-component multiwavelength composite beam is generated by polarization combination of the outputs of a pair of orthogonally polarized two-component multiwavelength lasers.

Abstract: Apparatus for mounting and aligning an optical element on a support structure comprises pivot means for mounting the element so that it can rotate about axes in two orthogonal directions and a pair of alignment means, each comprising a plunger and an inclined guide groove, for rotating the element about the two respective axes. Adjustment means, such as threaded screws, are provided for urging the plunger along the inclined grooves. The grooves are inclined at a sufficiently small angle to permit precision alignment. In order to reduce temperature sensitivity, the path of plunger motion is directed towards the pivotal centers and axes of the mount, and the optical element is placed on the axis between the pivot and the plunger.

Abstract: A flashlamp excited dye laser capable of high amplification and high pulse repetition rate. An active region of laser amplification is defined in a flowing dye by a long narrow channel created between confronting tube-shaped chambers. Laser excitation is directed into the channel through the transmissive walls of the chambers from flashlamps contained in each of the chambers, but which are thermally isolated from the dye channel. A specific geometry of the chambers provides a structural rigidity for long amplification channels.

Abstract: A system for temporal pulse shaping of laser radiation beams particularly for use as photoexcitation radiation in isotope separation. Each pulse of laser radiation is temporally segmented into two or more sections. The sections may be superimposed after a delay in the leading one to augment the pulse intensity, or the segmented pulses may be separately used as segments in a desired application, or the pulse rise time may be decreased by segmenting the pulse so as to permit rejection of the more slowly rising leading edge.

Abstract: A mirror for reflecting the high power radiation of laser beams while maintaining the predetermined shape of the reflecting surface. Radiation is reflected by a front, typically dielectric, surface on a transparent substrate. Since some power is unavoidably absorbed at the reflecting surface, the mirror will experience a thermal expansion. Some incident radiation is also transmitted to the opposite side of the substrate where at least a portion of the transmitted radiation is absorbed to a degree preselected to provide thermal expansion of that opposite side complementary to the expansion of the reflecting surface. The two expansions can be adjusted such that the shape of the reflecting surface is affected far less by the incident radiation than in the case where no opposite side absorption is provided.

Abstract: The ion separation electrodes in isotope separation apparatus are provided with removable collection shields to collect neutral particles which would normally pass through the ionization region. A preferred collection shield comprises a U-shaped section for clipping onto the leading edge of an electrode and a pair of flanges projecting substantially perpendicular to the clipping section for collecting neutral particles.

Abstract: An optical commutation system for commutating pulsed radiation between a common path of relatively high pulse rate and plural, closed spaced, slowly diverging paths on which the pulses are distributed. The system may thus act as a combiner or decombiner. The system employs a reflective or refractive optical element which is driven to produce a very slight oscillation in the orientation of the refractive or reflective surface of the element typically ranging over only a few degrees. The angle of oscillation is kept as small as possible, being only large enough to resolve or separate the radiation pulses on the slowly diverging paths. The very slight angular variation between adjacent ones of the diverging paths permits a large number of beams to be packed together in the bundle of diverging paths, but because of the slight angular variation, only a small angular scan resulting from the finite pulse duration is experienced. This can be kept well within acceptable limits for use with long path lengths.

Abstract: A CO.sub.2 medium is optically pumped by a five micron CO laser to the 03'0 level which radiates with 16 micron emission to the 02.degree.0 level. The resulting 16 micron laser finds application in laser uranium enrichment operating to provide excitation of uranium hexafluoride particles. Terminal level blockage, or bottlenecking, in the 02.degree.0 level is optionally avoided for continuous mode operation by 10 micron excitation with a CO.sub.2 laser from the 02.degree.0 to the 00.degree.1 level. The CO.sub.2 is then diluted by mixing nitrogen gas with it to promote energy transfer to the V=1 vibrational level of the nitrogen, thereby insuring maintenance of the inversion necessary for efficient, high power lasing in the 03'0 to 02.degree.0 transition.

Abstract: A system of wholly passive or static elements for increasing laser pulse rate by interleaving the pulses of a plurality of beams of pulsed laser radiation. The system of static elements includes an array of beam splitters which are operative to receive a plurality of beams of pulsed laser radiation and provide a plurality of output beams, each sharing the radiation in each of the input beams. The invention includes a methodology for expanding the array of beam splitter elements to combine any number of input beams, of whatever differing characteristics, to provide a corresponding number of output beams, each sharing a portion of the radiation in each of the input beams.