Abstract: A method and apparatus which corrects the amplutide variation in the output in an electro-optic modulated laser system (10). Birefringence within the electro-optic crystal (25) causes elliptical polarization of the linearly polarized laser light (22) produced by the laser gain medium (16), in turn causing a loss in the laser output (27). The loss owing to the elliptical polarization is corrected by either applying a D.C. bias from voltage source (30) directly to the electro-optic crystal (25) or by inserting a quarter-wave plate (32) within the laser's resonant cavity.

Abstract: To produce a medium for the emission of coherent radiation, i.e., a laser-active medium, using a complex of metastable helium and ammonia, it is proposed that it comprise a complex of metastable helium and ammonia as well as a radiation-active component, that the complex and the radiation-active component both be in the condensed, solid phase, and that the complex be present in the laser-active medium in condensed form with its dipole moment aligned substantially in one direction.

Abstract: An X-ray laser (10), and related methodology, are disclosed wherein an X-ray laser target (12) is illuminated with a first pulse of optical laser radiation (14) of relatively long duration having scarcely enough energy to produce a narrow and linear cool plasma of uniform composition (38). A second, relatively short pulse of optical laser radiation (18) is uniformly swept across the length, from end to end, of the plasma (38), at about the speed of light, to consecutively illuminate continuously succeeding portions of the plasma (38) with optical laser radiation having scarcely enough energy to heat, ionize, and invert them into the continuously succeeding portions of an X-ray gain medium. This inventive double pulse technique results in a saving of more than two orders of magnitude in driving optical laser energy, when compared to the conventional single pulse approach.

Abstract: A laser adapted to operate at a constant, predetermined wavelength includes the following elements disposed in order within a laser cavity and aligned along the path of light flow therethrough: a highly reflective rear mirror, a halfwave plate, a Brewster window, an active laser medium, and an output coupler. The halfwave plate is designed to rotate incident light beams by 180.degree. at the predetermined wavelength and to rotate incident light beams by an amount other than 180.degree. at wavelengths other than the predetermined wavelength. In a preferred embodiment, the Brewster window is a thin film polarizer designed for the predetermined wavelength.

Abstract: A mode-locked fiber laser having a length greater than 10 meters is equipped with an intracavity shutter or "mode-locking" device. The intracavity shutter is a broad bandwidth modulator which allows fast shutter on and off speeds, allowing short on times as well as short on-off and off-on transition times. The fiber and the modulator may be integrated. The fiber is comprised of a material doped with an active species having a long lifetime upper state, wherein the upper state lifetime is longer than the round trip time of a pulse through the fiber. The laser may be configured as either a linear laser or a ring cavity laser. The present invention allows short pulse widths with high pulse energies.

Abstract: Modelocking of a solid state laser such as a Ti:Al.sub.2 O.sub.3 laser is achieved by employing an external cavity defined by spatially separated reflective elements wherein at least one of the reflective elements exhibits a nonlinear characteristic in response to an impinging light beam. Exemplary nonlinear reflective elements are described using bulk semiconductor material or semiconductor quantum well structures integrated with a rear reflector such as a stack of quarter-wave thick dielectric or semiconductor material. Tuning control of the nonlinear reflective element may be introduced with temperature control arrangements and with mechanical translation arrangements in conjunction with lateral band gap engineering of the semiconductor material.

Abstract: A linear laser having a dual frequency output is shown where the output frequencies may be varied while maintaining a constant frequency separation. The laser includes a first fully reflective mirror spaced apart from a second partially reflective mirror defining a resonant cavity, a non-reciprocal element disposed within the cavity between the two mirrors, a magnetic field forming device at the non-reciprocal element and means for varying the resonant frequency of the cavity.

Abstract: An improved laser pumping apparatus in which a plurality of generally spherical beads are disposed in pumping energy transmitting juxtaposition with the active outer surface of a laser element so as to be positioned between the active outer surface of the laser element and a pumping energy source. in a neodymium doped yttrium aluminum garnet laser element pumped by a flash lamp, the beads are made of silicon. The beads are approximately 50 to 100 microns in diameter and may be attached directly to the active outer surface of the laser element, such as by using a pumping energy transmitting adhesive, or the beads may be attached to an intermediate transparent or translucent pumping energy transmitting member such as a thin sleeve that fits over a laser element configured as a rod.

Abstract: The present invention relates to an optoelectronic integrated circuit having a substantially planar surface and which includes at least one laser diode and at least one field effect transistor. The integrated circuit comprises a substrate of semi-insulating GaAs having on a surface thereof in succession a first clad layer, a first confinement layer, a quantum well active layer, a second confinement layer, a second clad layer and an FET active layer. The FET active layer is of a material having good field effect transistor characteristics, such as N type GaAs or N type A1GaAs over a layer of undoped GaAs. The quantum well active layer is formed of alternating layers of undoped GaAs and a material which is capable of generating light of a wavelength longer than can be absorbed by the FET active layer, such as undoped InGaAs. The laser diode includes spaced contact regions of opposite conductivity type extending through the layers to the quantum well active layer.

Abstract: An X-ray laser (10) that lases between the K edges of carbon and oxygen, i.e. between 44 and 23 Angstroms, is provided. The laser comprises a silicon (12) and dysprosium (14) foil combination (16) that is driven by two beams (18, 20) of intense line focused (22, 24) optical laser radiation. Ground state nickel-like dysprosium ions (34) are resonantly photo-pumped to their upper X-ray laser state by line emission from hydrogen-like silicon ions (32). The novel X-ray laser should prove especially useful for the microscopy of biological specimens.

Abstract: A room temperature solid state laser for producing a laser emission at a wavelength of substantially 1.96 microns is disclosed. In a preferred embodiment, the laser includes: a laser cavity defined by a plurality of coated reflective elements to form a reflective path thereamong; a laser crystal disposed in the laser cavity and capable of lasing at substantially 1.96 mircons and 2.01 microns when excited; and means for exciting the laser crystal to lase at substantially 1.96 microns and at substantially 2.01 microns. The laser crystal is comprised of a host crystal material capable of accepting Cr.sup.3+ and Tm.sup.3+ ions. Through their respective reflectivities at each of the wavelengths at substantially 1.96 microns and 2.01 microns, the coated reflective elements collectively operate to produce substantial loss in radiation at the wavelength of substantially 2.

Abstract: Apparatus and method for modulating the phase or the amplitude of a monochromatic light beam, the apparatus including in one embodiment a Mach-Zehnder interferometer that consists of two beam splitters or beam combiners, a fully reflective mirror and an electro-optical crystal for modulation of one of two beam components. The electro-optical crystal serves as an optical resonator for the portion of the light beam admitted into the crystal material, using total internal reflection of the light beam from two or more of the crystal surfaces. The crystal has a high finesse so that a relatively small change in voltage applied across the crystal produces a large (.apprxeq.180.degree.) change in the external phase shift associated with the modulated component of the light beam.

Abstract: A laser diode impulse circuit has a normally forward biased step recovery diode coupled to the output of a current pulse generating circuit. An inductor in parallel with a series combination of a pulse shaping network and a laser diode is coupled to the output of the step recovery diode. When the step recovery diode becomes reverse biased in response to a current pulse from the current pulse generating circuit, energy is stored in the inductor. The stored energy is then transferred from the inductor to the laser diode via the pulse shaping network to produce an optical pulse having a desired shape.

Abstract: A tunable semiconductor diode laser with distributed reflection (DBR semiconductor laser) having a wide wavelength range is a suitable transmitter or local oscillator in a receiver in heterodyne and coherent optical glass fiber communication systems. Such a diode includes, in addition to the Bragg section in which the Bragg reflection takes place, an active section in which the radiation-emitting active region is present. When such a semiconductor diode laser is further provided with a so-called phase section, tuning is possible over a large wavelength range within one oscillation mode. A laser which is continuously tunable over the whole wavelength range is obtained by provided a mechanism by which the intensity of radiation which is reflected at the junction between the active section and the phase section is made low with respect to the intensity of the radiation which returns from the phase section to the active section.

Abstract: A laser diode control circuit maintains a desired average output power of the laser diode by detecting the optical output, amplifying the detected output, and controlling a bias current of the laser diode accordingly. A pilot tone is combined with the detected output and amplified therewith, and the amplified level of the tone is detected and used to control a modulation current for the laser diode. In one described arrangement the laser diode is controlled to have a high extinction ratio with the bias current at the knee of the diode's characteristic curve, and in another arrangement a lower extinction ratio is provided with the bias current above the knee.

Abstract: A mutually pumped phase conjugator (MPPC) is used to remove spatial distortions from a high power laser beam. The high power beam with its "dirty" spatial profile is directed into one side of the MPPC. A spatially clean beam at the same nominal frequency as the high power beam is output from a continuous wave (CW) laser and directed into the opposite side of the MPPC. As a result of mutually pumped phase conjugation, the MPPC returns a phase conjugate beam that retains the clean spatial profile of the CW beam but acquires the temporal characteristics of the high power beam. A Faraday isolation system may be used to separate the phase conjugate beam from the incident CW beam to provide an output beam having a clean spatial profile. If desired, the high power beam can be transformed into an image bearing output beam simply by modifying the incident CW beam with a transparency or spatial light modulator.

Abstract: A double conjugate laser beam amplifier which twice conjugates the laser ut beam and provides an output beam in exactly the same direction and of the same polarization as the input beam while retaining the alignment stability of singly conjugated amplifiers even when the thin film polarizer between two conjugate amplifiers is not stable. A half-wave voltage at a Pockels cell positioned on the beam axis immediately prior to the polarizer controls whether the oscillator beam is transmitted through the polarizer or is reflected off the polarizer toward a first conjugate amplifier for amplification and retroflection back through the first conjugate amplifier and the polarizer into a second conjugate amplifier for further amplification and retroreflection back and is reflected off the polarizer a second time. The double conjugate amplifiers may be cascaded to both increase output and laser beam pulse repetition rate.

Abstract: A diode laser amplifier used as a clocked optical regenerator and other diode laser amplifier optoelectronic functional circuits are disclosed. In the regenerator circuit (101), the input optical pulse data signal to be regenerated is inputed to a diode laser amplifier (102), the gain of which is modulated by a clock signal electronically recovered from and synchronized with the input data signal. By modulating the gain so that it is substantially attenuated during essentially half of each bit interval, and at a high gain level during the other half of the bit interval, each pulse in the input signal is both amplified and "cleaned up" produce an output pulse signal that is an amplified, reshaped and retimed version of the input optical signal.

Abstract: An improved electrode design for reducing discharge instability, especially in white light lasers. The apparatus consists of at least one cathode electrode (12) arranged between anode electrodes (14), said cathode being divided into two equally long tube parts (15) designed with inner cylindrical electrode surfaces (A.sub.1, A.sub.2) between which a widened portion (16) is located and each anode electrode is connected via and insulator (13) to the end of each tube part (15) facing away from the widened portion. This widened portion of the cathode serves to divide the cathode which in turn stablized the current and the current density. It can also serve as a metal reservoir.

Abstract: A tunable solid state laser having a titanium:sapphire grain medium and a birefringent filter mounted within a resonant cavity is provided. The resonant cavity is longitudinally pumped. The cavity is enclosed in a casing which has a small window admitting the pump beam into the resonant cavity, and a small window with an anti-reflection coating allowing the laser output to exit the casing. The casing is maintained at a positive pressure of nitrogen gas during operation of the laser to purge the resonant cavity of air and water vapor.