Abstract: A conformal coherent wideband antenna coupled IR detector array included a plurality of unit cells each having a dimension that includes an antenna for focusing radiation onto an absorber element sized less than the dimension. In one embodiment, the absorber element may be formed of a mercury cadmium telluride alloy. According to a further embodiment, the antenna array may be fabricated using sub-wavelength fabrication processes.

Abstract: A conformal coherent wideband antenna coupled IR detector array included a plurality of unit cells each having a dimension that includes an antenna for focusing radiation onto an absorber element sized less than the dimension. In one embodiment, the absorber element may be formed of a mercury cadmium telluride alloy. According to a further embodiment, the antenna array may be fabricated using sub-wavelength fabrication processes.

Abstract: A method and apparatus for compensating for phase fluctuations incurred by an optical beam travelling through free space, especially a turbulent atmosphere. A transmitting station transmits a plurality of uniquely tagged optical beams through free space. The plurality of uniquely tagged optical beams are received at a receiving station, where a parameter of each uniquely tagged optical beam is quantified. Information associated with the quantified parameter for each uniquely tagged optical beam is then sent back to the transmitting station via a wireless feedback link. Using the information, the transmitting station adjusts at least one uniquely tagged optical beam to compensate for phase fluctuations.

Abstract: A limiter for limiting selected frequency components by generating Stokes waves in a stimulated Brillouin scattering medium. The generated Stokes waves create a seed that is provided to another stimulated Brillouin scattering medium. The seed selecting the undesired frequency components to be attenuated.

Abstract: A limiter for limiting selected frequency components by generating Stokes waves in a stimulated Brillouin scattering medium. The generated Stokes waves create a seed that is provided to another stimulated Brillouin scattering medium. The seed selecting the undesired frequency components to be attenuated.

Abstract: A method and apparatus for compensating for phase fluctuations incurred by an optical beam travelling through free space, especially a turbulent atmosphere. A transmitting station transmits a plurality of uniquely tagged optical beams through free space. The plurality of uniquely tagged optical beams are received at a receiving station, where a parameter of each uniquely tagged optical beam is quantified. Information associated with the quantified parameter for each uniquely tagged optical beam is then sent back to the transmitting station via a wireless feedback link. Using the information, the transmitting station adjusts at least one uniquely tagged optical beam to compensate for phase fluctuations.

Abstract: A limiter for limiting selected frequency components by generating Stokes waves in a stimulated Brillouin scattering medium. The generated Stokes waves create a seed that is provided to another stimulated Brillouin scattering medium. The seed selecting the undesired frequency components to be attenuated.

Abstract: A laser comprising a master oscillator and a loop phase conjugate mirror (Loop-PCM) for substantially eliminating transient relaxation oscillations to instead form controlled sustained pulsations. In a preferred embodiment suitable for material processing applications with high power requirements, the master oscillator is part of a Phase Conjugate Master Oscillator Power Amplifier (PC-MOPA). A method for processing a material using a Loop-PCM by determining and using an optimal pulse fluence, duration and spacing is provided. Using pulses of the kind which are produced by the transient, and normally not desirable, relaxation oscillations common to Nd:YAG and other lasers, relaxation oscillations with controllable pulse duration, repetition rate and duty cycle are generated, making it ideal for materials processing.

Abstract: A Yb-doped cladding pumped fiber laser includes a reflective grating located at each distal end of the laser cavity. Each reflective grating can reflect light propagating inside a fiber core and at a desired wavelength range. A plurality of band-rejecting gratings are disposed between the reflective gratings, whereby the band-rejecting gratings can couple light at an undesired wavelength range and out of the fiber core. When the band-rejecting gratings are in an end-to-end relationship, they are separated by a distance of approximately L whereby L=[(.sigma..sub.e.sup.d +.sigma..sub.a.sup.d)ln 1/T]/[n(.sigma..sub.a.sup.d .sigma..sub.e.sup.u -.sigma..sub.e.sup.d .sigma..sub.a.sup.u)], n is a concentration of ions subject to excitation, .sigma..sub.a.sup.d is an absorption cross section at said desired wavelength range, .sigma..sub.e.sup.u is an emission cross section at said undesired wavelength range, .sigma..sub.e.sup.d is an emission cross section at said desired wavelength range, .sigma..sub.a.sup.

Abstract: A loop four-wave mixing phase conjugator that can be used with depolarized signal beams comprises a polarization separator, a polarization mixer, an optical diode, a gain medium and relay optics that together form a unidirectional laser resonator. In operation, the polarization separator separates a signal beam .epsilon..sub.1 into orthogonally polarized signal beam components .epsilon..sub.11 and .epsilon..sub.12 and directs them to a nonlinear medium. The components propagate through the nonlinear medium and emerge as loop beam .epsilon..sub.2, with orthogonally polarized components .epsilon..sub.2 and .epsilon..sub.22. The polarization mixer mixes the energy from the two orthogonally polarized loop beam components, and relay optics direct the loop beam components back to the nonlinear medium at an angle with respect to the input beam. The loop beam components intersect and optically interfere with signal beam components .epsilon..sub.11 and .epsilon..sub.22 in the nonlinear medium to form gratings.

Abstract: A compact loop four-wave mixing phase conjugator that can be used in practical optical applications comprises a reflective nonlinear cell, relay optics, an optical gain medium, and an optical diode that together form a unidirectional ring laser resonator. In operation, a signal beam .epsilon..sub.1 is directed to the nonlinear cell, where it passes through a nonlinear medium contained within the cell and is reflected out of the cell as loop beam .epsilon..sub.2. The relay optics direct loop beam .epsilon..sub.2 through the optical diode, optical gain medium, and back to the nonlinear cell, where it intersects and optically interferes with the signal beam .epsilon..sub.1 to form a refractive index grating in the nonlinear medium. The optical diode and gain medium are positioned in the loop so that an oscillation beam .epsilon..sub.3 builds up from optical noise in the resonator and oscillates in a direction counter to the propagation direction of loop beam .epsilon..sub.2. A portion of oscillation beam .

Abstract: Laser beam speckle effects are mitigated by frequency chirping a single-mode laser beam, reflecting it off a speckling surface, and then integrating the reflected beam over at least one chirp period. The speckle reduction is comparable to the use of a multi-longitudinal mode beam having a bandwidth similar to the chirped frequency excursion, while leaving the beam compatible with nonlinear optical processes that are not compatible with multi-longitudinal mode beams. Where the nonlinear process is stimulated Brillouin scattering (SBS) phase conjugation, the beam can be chirped at a rate up to the order of ##EQU1## where .DELTA..nu..sub.B is the gain bandwidth and L is the effective SBS interaction length of the phase conjugator, and C is the speed of light. Other nonlinear processes with which the beam may be used include harmonic generation and Raman-based beam cleanup or wavelength conversion.

Abstract: Optical energy transfers, via stimulated scattering, to a seed beam from a pump beam that has a non-uniform optical intensity distribution are made with an enhanced spatial uniformity of amplification by spatial mixing of the pump beam within the medium where amplification takes place. In a stimulated Brillouin scattering (SBS) phase conjugate mirror (PCM) having an amplifier and a phase conjugating oscillator, beam mixing elements are provided on opposite sides of the amplifier to mix both the input and return phase conjugated beams within the amplifier, and to restore the beams after they have exited. The preferred mixing mechanism is a plurality of cylindrical lenses that are spaced along the beam path, and/or have unequal focal lengths to produce a series of foci within the amplification medium that are rotated with respect to each other. Amplitude replication as well as high fidelity phase conjugation are enhanced using SBS.

Abstract: The output of an optical device which involves a stimulated brillouin scattering (SBS) gain medium is enhanced over a range of input beam intensities by providing a gain medium which has a given SBS gain for a given input beam intensity, and modifying the gain medium to reduce its SBS gain coefficient. By lowering the SBS gain coefficient, SBS dominance and suppression of stimulated Raman scattering (SRS) can be mitigated, and the output fidelity of a phase conjugation system with respect to its input can be significantly enhanced. Mechanisms for reducing the SBS gain coefficient include increasing the medium viscosity, thermal conductivity and/or diffusion coefficient, or causing the medium relaxation zone to coincide with the frequency of the phonons involved in the SBS process. Two different media can be mixed together in varying proportions to progressively modify the overall medium SBS gain as the input beam intsnsity is progressively changed.

Abstract: Integrated laser head apparatus is disclosed for producing high energy pulses in pulsed gas lasers. The present invention provides high energy pulses over short time durations suitable for laser rangefinder systems due to an improvement in the arrangement of energy storage capacitors (22, 24) which keeps circuit inductance to a minimum. The pair of nested, ceramic capacitors (22, 24) are substantially cylindrical and are coupled through thin conductive layers (23). The capacitors are charged by a spark gap trigger (14), an inductor (18), and a charging resistor (52). The capacitors (22, 24) enclose a pressure vessel (28) which further encloses a laser resonator (12) including a laser output coupler mirror (42), totally reflective mirror (44), discharge electrodes (32, 34) and a central chamber (30) which contains a pressurized gaseous phase laser medium. The high voltage discharge electrode (32) is disposed coaxially with the surrounding capacitors (22, 24).