Abstract: Various examples of an optically pumped laser are described. In each example, a laser member formed from active laser material is located in an optical cavity and a source of pumping light is arranged so that pumping light passes into the laser member through a side surface. A deflecting means is provided which ensures that the pumping light makes an initial pass followed by at least one, and preferably at least two, further passes across the laser member. In the further passes, the pumping light has a substantial component long the optical axis. Consequently, a relatively long absorption path for the pumping light is achieved. In one example, the laser member is an Nd:YAG bar (20), the pumping light source is an array (23) of laser diodes, and the deflecting means takes the form of a series of facets (27) formed along a side of the bar (20). In another example, the deflecting means is a diffraction grating.

Abstract: An actively stabilized laser is disclosed which includes a temperature tunable etalon in the laser cavity for single frequency operation. The operation of the laser is actively monitored to detect variations induced by changes in the length of the resonator. These changes tend to cause the frequency of the selected longitudinal mode to shift so that it is no longer aligned with the peak of the transmission curve of the etalon. When this misalignment occurs, operation deteriorates. By monitoring laser performance, the misalignment can be detected and the temperature of the etalon can be changed to realign its transmission peak to the selected mode. In the preferred embodiments, either the laser output power or the current supplied to the laser is monitored. This approach substantially reduces mode hopping.

Abstract: A gas laser device comprises a discharge space in which a laser gas is excited by electric discharge, the discharge space being in the form of a slab whose section perpendicular to a laser optical axis has a longer side and a shorter side; and laser resonator mirrors disposed at both ends of the discharge space, respectively. The laser resonant mirrors constitute a negative branch unstable resonator in a first dimension of longer side of the discharge space section, and a laser beam is obtained at one end of the longer side of the discharge space section.

Abstract: A light amplifying device comprising an optical oscillator constituted by first and second reflective mirrors and a common reflective mirror disposed in an optically opposite relation to each other, a polarized beam splitter for making a laser beam incoming from the side of the common reflective mirror incident on the first or second reflective mirror, and for making laser beams incoming from the sides of the first and second reflective mirrors incident on the common mirror, first and second amplifying media disposed in optical paths of the respective laser beams for amplifying the laser beams, and an optical element for rotating the polarizing plane of the laser beam reflected by the common reflective mirror by a predetermined angle.

Abstract: The present invention proposes a dielectric waveguide formed on a substrate of ultra-low thermal expansion glass which is assembled with a commercially available diode laser to create a temperature stabilized laser. The waveguide comprises multiple dielectric films which have equal and opposite temperature induced changes in refractive index with respect to each other into which is formed a Bragg grating, the grooves of which are sufficiently shallow to allow penetration of light into the waveguide of 1 mm to 1 cm. This provides a signal which is both narrowband and frequency stable so that the optical signal can be guaranteed to remain in a given narrow frequency band. The dielectric layers are deposited using ion assisted deposition (IAD) to provide uniform, high density films with reduced index-temperature coefficients and increased density, resulting in a waveguide with near-zero temperature variations in refractive index.

Abstract: The injection current for a laser diode is modulated so that a pregiven coherence function is obtained which drops off continuously at both ends outside of the coherence length. Several laser diodes are used for a very short coherence length for which the modulated wave numbers of the emitted radiation follow one another or overlap.

Abstract: Amplitude noise is dramatically reduced in an optically pumped modelocked laser arrangement by incorporating an intra-cavity or external cavity mode selection element with a continuous-wave pump laser coupled optically to a modelocked laser. The mode selection element causes a light beam generated from the pump laser to operate nominally at a single frequency, that is, substantially a single longitudinal mode. Mode selection may be realized with an air-spaced or solid material Fabry-Perot etalon.

Abstract: Mode-locked pulsed output is induced in a laser by introducing a varying frequency dependent loss in the cavity. The varying, frequency dependent loss allows a large number of longitudinal modes to oscillate. In one of the preferred embodiments of the subject invention, the varying frequency dependent loss is generated by reciprocating one of the mirrors of the resonator. In this embodiment, the laser has a resonator with a primary light path defined by first and second end mirrors. A gain medium is located between the end mirrors. A beam splitter is provided for redirecting the light into a secondary light path. A third mirror functions to feed back the light into the primary light path. Pulse formation is induced by varying the path length of one of the two paths by reciprocating an end mirror. Moving the mirror creates varying interference effects when the light energy is recombined at the beam splitter. The mirror is reciprocated relatively slowly, yet ultra-short pulses are generated.

Abstract: A semiconductor laser controller converts the light output of the driven laser to a photovoltaic current proportional to that light output and separates the current into high and low frequency components. A negative feedback loop controls the forward current of the laser such that the sum of these high and low frequency components of the photovoltaic current equal a reference signal current defining the light output of the laser. A control unit controls the reference current such that a voltage proportional to the low frequency component of the photovoltaic current equals a reference voltage corresponding to the reference current.

Abstract: An optical parametric oscillator capable of operating in the 0.300 to 0.400 micrometer wavelength range is disclosed. The oscillator includes a cavity defined at its ends by a pair of cavity resonator mirrors. A nonlinear optical crystal is positioned on the optical axis of the cavity intermediate the mirrors and is rotatable about a crystalline axis to tune the oscillator. A pair of pump steering mirrors are mounted in the cavity, one mirror between each resonator mirror and the corresponding end of the crystal. A source of pumping energy supplies energetic light to the cavity, the pumping beam being directed into the cavity and onto a first steering mirror, thence through the crystal and to the second steering mirror which then directs the pumping beam out of the cavity. The pumping beam may be at a wavelength of 266 nm, for example, to produce an output wave from the oscillator within the range of interest.

Abstract: Crystals of compounds of the type (RE).sub.x Y.sub.1-x Al.sub.3 (BO.sub.3).sub.4 where (RE) is a rare-earth element or absent (x=O) are optically uniaxially negative and show the linear electrooptical effect and the nonlinear optical effect. They are useful as modulators and as nonlinear optical devices such as second harmonic generators, parametric oscillators and amplifiers, and the like.

Abstract: In the present invention a nonlinear crystal of an optical parametric oscator is provided with a pump pulse and electrodes for applying a high voltage to the crystal during the pump pulse. The high voltage is switched from one level to another during the pump pulse duration. The initial value of the high voltage determines the position of the frequency center of the optical parametric oscillator gain profile because the indices of refraction are a function of the applied voltage due to the electro-optic effect. During the pump pulse, when the high voltage is switched to some other value, a new set of momentum and energy conservation conditions results. This causes a frequency shift in the gain profile. Thus the oscillator is provided with two differing gain profiles during the pump pulse. The output frequency of the oscillator is only those frequencies in both gain profiles.

Abstract: A method and system for stabilizing the output frequencies of a multimode laser of the type which operates in at least three optical cavity modes includes detecting the intermodulation product frequency, using a suitable photodetector. The optical cavity modes may be either purely longitudinal for a single transverse mode, or may include radiation from multiple transverse cavity excitations, also with possible longitudinal plurality. The detector output is monitored for the intermodulation product beat signal which is contained in the detector current at the differences of the primary difference frequencies of the optical modes. A signal derived from the frequency of the intermodulation product term is compared with a reference signal, and the resulting error signal is driven to zero by varying the optical length of the laser oscillator cavity in response to the error signal, thereby causing the operating modes of the laser to be stabilized.

Abstract: A method of stabilizing the frequency of a semiconductor laser comprises stabilizing a time-dependent frequency fluctuation by utilizing an optical energy absorption medium including an isotope acetylene gas molecule. An apparatus for stabilizing the frequency of a semiconductor laser, comprises a semiconductor laser, an optical energy absorption medium, a photodetector and a control circuit as essential elements. The optical energy absorption medium includes an isotope acetylene molecule.

Abstract: For power lasers, the shape of the mirror is an essential factor for the quality of the mode. In addition, a power laser usually has a plurality of mirrors. The shape of the mirrors may change during operation, for example due to heating. According to the invention, a hollow space is provided on the rear side of the mirror and pressure is applied to this hollow space to a greater or lesser degree, so that the geometry of the mirror changes under its influence.

Abstract: A ring laser is disclosed that produces a single frequency of laser radiation in either the pulsed mode of operation or the continuous waveform (cw) mode of operation. The laser comprises a ring laser in a bowtie configuration, a birefringent gain material such as Nd:YLF, an improved optical diode that supports laser oscillation having a desired direction of travel and linear polarization, and a Q-switch. An output coupler (mirror) having a high reflectivity, such as 94%, is disclosed. Also disclosed is a self-seeded method of operation in which the laser can provide a pulse or a series of pulses of high power laser radiation at a consistent single frequency with a high degree of amplitude stability and temporal stability. In operation, the laser is operated in continuous waveform (cw) at a low power output with the Q-switch introducing a loss into the resonating cavity. Pumping is continued at a high level, causing the gain material to store energy.

Abstract: A commercial near resonant laser system with a trivalent rate earth ion doped solid state host, such as Nd:YAG, is pumped at an energy sufficient to excite the electrons from the ground level directly to the upper laser level. The laser system is then tuned to a transition from the upper laser level back to the ground level to produce high power output beams. Because the ground level will include a plurality of "Stark split levels", the necessary population inversions can be maintained and laser energy generated. However, the difference between the Stark split level from which the electrons are excited to the upper laser level, and the Stark split level to which the electrons decay in the light producing transition from the upper laser level, is slight. Thus, energy dissipated in heat as electrons decay in non-lasing transitions is minimized.

Abstract: A method and apparatus for precisely aligning waveguide lasers. Each optical element of a waveguide laser is systematically and independently adjusted relative to pertinent waveguide segments. A test laser beam is propagated into a waveguide segment which is adjacent to a selected end port substantially parallel to the longitudinal axis running through the center of the waveguide segment so that the test laser beam contacts opposing wall portions along two axes of the selected end port. The test laser beam is reflected through each successive waveguide segment, the diffraction patterns of the reflected test laser beam are detected at the end opposite the reflecting means, and the reflecting elements are adjusted until the diffraction patterns of the reflected test laser beam are substantially symmetrical.

Abstract: The frequency conversion element for producing light of higher harmonic wave from the fundamental wave laser oscillator is provided with strain gauges 4, 4 or piezoelectric elements 4', 4' or thermo-couples 6, 6, output signals whereof are led to a signal processor and to a comparator, thereby to issue a control signal to decrease power of the input laser light, to prevent thermal breakdown of the frequency conversion element.

Abstract: A laser oscillator system which transmits laser input beam pulses through optical diode and into a plurality of time-multiplexed phase conjugate amplifier which sequentially amplify in chronological order subsequent input beam pulses. The optical diode is positioned on the oscillator laser beam pulse axis and is comprised of a polarizer, a half-wave plate which rotates the pulse polarity by 45.degree. in one direction and a Faraday rotator which rotates the pulse polarity 45.degree. in the opposite direction. A plurality of grouped Pockels cells and polarizers are positioned on the oscillator axis past the Faraday rotator. The polarizers route the input beam pulse toward a phase conjugate amplifier when a half-wave voltage is applied to the Pockels cell. Each phase conjugate amplifier has a phase conjugate mirror, at its output for retroreflecting the once amplified input laser beam pulse back therethrough for a second amplification.