Abstract: An optical parametric oscillator or OPO (20) includes an elongated resonant cavity (22) for signal light, having a parametric gain medium (28) disposed therein for converting pump light to signal light. The resonant cavity has a output coupling device (26) at one end thereof and a Porro prism (24) at the opposite end thereof. The OPO includes an optical arrangement (30, 39 and 40) for directing pump light to make counterpropagating initial and return passes longitudinally through the gain medium at an angle (36) to the axis (23) of the resonant cavity.

Abstract: A distributed gain medium, such as an optical fiber, is configured as a Sagnac interferometer or loop mirror, and this mirror is used as at least one of the two reflectors in the amplifier or laser. The distributed gain medium produces optical signal gain through nonlinear polarization, that may cascade through several orders. The Sagnac interferometer or loop mirror defines two optical paths that will support both common mode and difference mode optical signals. Pump fluctuations resulting from higher cascade orders are at least partially rejected through the difference mode signal path, thereby reducing the overall effect of pump fluctuation. The result is a broadband optical resonator, suitable for use at a variety of different wavelengths, including 1.3 .mu.m and 1.55 .mu.m wavelengths. Amplifiers based on this technology are "four-level," providing a pass through signal even when the pump laser is not functioning.

Abstract: A travelling-wave semiconductor laser amplifier having suppressed self-oscillation is provided. When incorporated into a master oscillator power amplifier device, such a device has improved light output versus amplifier current characteristics. Also provided is a method for suppressing self-oscillation in travelling-wave semiconductor laser amplifier structures for improving the characteristics of the device into which the amplifier is incorporated.

Abstract: An optoelectronic semiconductor device with at least one laser and two mutually parallel, strip-shaped active regions, whose ends are optically coupled at one side, is a very suitable radiation source or amplifier, for example as a tunable radiation source. More than one kind of radiation is often present in such a device, whereas it is desirable for only one kind of radiation to pass through a gate of the device. To achieve this in prior devices, an additional component, such as a filter or isolator, is necessary.

Abstract: A long pulse laser system emits 500-1000 ns quasi-rectangular pulses at 527 nm with near diffraction-limited divergence and near transform-limited bandwidth. The system consists of one or more flashlamp-pumped Nd:glass zig-zag amplifiers, a very low threshold stimulated-Brillouin-scattering (SBS) phase conjugator system, and a free-running single frequency Nd:YLF master oscillator. Completely passive polarization switching provides eight amplifier gain passes. Multiple frequency output can be generated by using SBS cells having different pressures of a gaseous SBS medium or different SBS materials. This long pulse, low divergence, narrow-bandwidth, multi-frequency output laser system is ideally suited for use as an illuminator for long range speckle imaging applications. Because of its high average power and high beam quality, this system has application in any process which would benefit from a long pulse format, including material processing and medical applications.

Abstract: A laser system capable of providing light of high intensity is disclosed. This system includes a laser gain medium and three reflectors. A first reflector and a second reflector spaced from the first reflector define a laser cavity that contains the laser gain medium. The second reflector has a reflectivity (R.sub.2) larger than the reflectivity (R.sub.1) of the first reflector such that light emitted from the laser gain medium resonates in the laser cavity. A third reflector having a reflectivity (R.sub.3) larger than the reflectivity of the first reflector (R.sub.1) is spaced from the second reflector to define a resonant cavity external to the laser cavity. Light passes from the laser cavity to resonate in the external resonant cavity. Part of the light passes from the external resonant cavity to the laser cavity to optically lock the laser gain medium. The distance between the second and the third reflectors is adjustable to tune the resonant frequency of the external cavity.

Abstract: A multiple-pass laser amplifier that uses optical focusing between subsequent passes through a single gain medium so that a reproducibly stable beam size is achieved within the gain region. A confocal resonator or White Cell resonator is provided, including two or three curvilinearly shaped mirrors facing each other along a resonator axis and an optical gain medium positioned on the resonator axis between the mirrors (confocal resonator) or adjacent to one of the mirrors (White Cell). In a first embodiment, two mirrors, which may include adjacent lenses, are configured so that a light beam passing through the gain medium and incident on the first mirror is reflected by that mirror toward the second mirror in a direction approximately parallel to the resonator axis. A light beam translator, such as an optical flat of transparent material, is positioned to translate this light beam by a controllable amount toward or away from the resonator axis for each pass of the light beam through the translator.

Abstract: An apparatus for stretching or compressing an ultrashort pulse in time that is free of non-linear and spatial distortion (temporal or spatial frequency chirp) comprises a first diffraction grating G, a concave spherically curved mirror [CCM] with a radius of curvature R.sub.1, a convex spherically curved mirror [CXM] with a radius of curvature R.sub.2, and a flat reflector, [PM]. As a result of propagation of the ultrashort input pulse through this system, the output pulse is either stretched (or compressed) in time so that it now has a duration many times longer (or many times shorter) than its input pulse duration, is spatially uniform (i.e. has no spatial chirp,) and collimated. It can be separated from the input pulse by passage through a Faraday isolator.

Abstract: Stability of a pump laser for activating an erbium amplifier is enhanced by a grating which results in laser operation in the coherence collapse regime.

Abstract: A multiple-pass laser amplifier that uses optical focusing between subsequent passes through a single gain medium so that a reproducibly stable beam size is achieved within the gain region. A resonator or a White Cell cavity is provided, including two or more mirrors (planar or curvilinearly shaped) facing each other along a resonator axis and an optical gain medium positioned on a resonator axis between the mirrors or adjacent to one of the mirrors. In a first embodiment, two curvilinear mirrors, which may include adjacent lenses, are configured so that a light beam passing through the gain medium and incident on the first mirror is reflected by that mirror toward the second mirror in a direction approximately parallel to the resonator axis. A light beam translator, such as an optical flat of transparent material, is positioned to translate this light beam by a controllable amount toward or away from the resonator axis for each pass of the light beam through the translator.

Abstract: A semiconductor optical amplifier device has an amplification factor that does not vary even if an injection current thereinto is changed. The semiconductor amplifier device includes a laser structure and an active region formed in the laser structure along a waveguide thereof. The active region is constructed so that a carrier density distribution and a light distribution in the active region cooperate to keep a resonator length of the laser structure unchanged irrespective of the change in the injection current into the laser structure.

Abstract: Resonant cavity apparatus comprise a Fabry-Perot optical resonant cavity of a type having families of transverse modes between longitudinal TEM.sub.00 modes. In such resonant cavity apparatus and in methods of minimizing the effect of transverse modes, families of such transverse modes are merged into longitudinal TEM.sub.00 modes of the non-confocal Fabry-Perot optical resonant cavity, providing superior optical performance. This may be manifested by a transmission spectrum similar to that of a flat-flat Fabry-Perot cavity, but with superior Finesse and transmission efficiency.

Abstract: An active ring laser gyroscope having two optical amplifier diodes therein which are switched in such a fashion that the two counter propagating light pulses in the ring are never in an activated optical amplifier diode at the same time.

Abstract: A process and apparatus for the modulation and amplification of light beams having at least one input light beam (8) supplied to at least one Fabry-Perot resonator having at least one resonance mode, and defined by two mirrors (M1,M2) and produced by stacking layers on a substrate (4). At least one of the layers form an active medium (6) able to amplify the input light beam by stimulated emission, the wavelength thereof being around the resonance of the resonator and the density of free charge carriers in the active medium being varied in such a way as to make the latter sometimes absorbent and sometimes an amplifying with respect to the input beam and thus obtain at least one output light beam (10) whose intensity is modulated and amplified relative to the input beam. Application to optical telecommunications and to optical interconnections.

Abstract: A slab laser amplifier array includes a plurality of parallel, stacked, laser resonators, with each resonator having a walk-off mode of propagation of laser light from an input side of the resonator to an output side of the resonator where the exiting light diffracts around the resonator mirror. A source of a plurality of phase related, for example co-phasal, light beams supplies phase related light to each input side. The source of phase related light may be a source of one single mode beam followed by a telescope with an aperture having plural stops or a co-phasal array of laser resonators. A laser array of open resonators also has circular concentric electrodes.

Abstract: A laser device utilizes a turbojet engine to provide a stimulation source. The turbojet engine is conventional, having a compression section, a fuel injection and igniting section, and an afterburner section. A pair of mirrors are mounted adjacent the hot gaseous stream produced by the turbojet engine. One of the mirrors is fully reflective and the other is partially reflective. The mirrors face each other and are perpendicular to the flow of the gaseous stream, creating a reflection path that is transverse to the flow. The high temperature creates excited molecules in the gaseous stream. This results in photons being emitted, which when striking other excited atoms which emit photons of the same wavelength, create additional photons to combine into a laser beam travelling along a reflection path between the mirrors. A portion of the laser beam passes through the partially reflecting mirror where it strikes an inclined mirror that aims the beam toward a desired target.

Abstract: A coherent light source, such as a laser oscillator and a monolithic MOPA device, and a broad area light amplifying device, all characterized by having a leaky waveguide beam expander coupled thereto for expanding a single mode beam into a wide light beam in a coherent manner. The beam expander comprises an elongated antiguide core of a first refractive index and a radiated-wave receiving region of a higher refractive index to receive lightwaves laterally radiated from the antiguide core. This beam expander can be located at an output end of a single mode laser oscillator to receive and expand the beam, at an input end of a broad area optical power amplifier to allow the amplifier to accept a narrow input beam, or between the laser oscillator and power amplifier in a MOPA device. The beam expander elements can also be located partially or entirely within the resonant optical cavity of a laser oscillator.

Abstract: An optically active device comprising an optical fiber, a light source and a coupler is disclosed. The optical fiber has a core made of a silicate glass containing Rb and/or Cs oxide. The core is doped with Nd.sup.3+ as an active ion and transmits light at 1.3 .mu.m band. The light source generates excitation light at 0.8 .mu.m. The coupler directs the excitation light from the light source into the core of the optical fiber. A signal light or a spontaneous light at 1.3 .mu.m band which is transmitted in the core stimulates Nd.sup.3+ to emit light at 1.3 .mu.m band. As a result an optical function such as optical amplification can be effected at 1.3 .mu.m band.

Abstract: Novel optical fiber devices (amplifiers and lasers) are disclosed. The devices comprise one or more optical "cavities", depending on the type of device. The cavities typically are formed by means of in-line refractive index gratings in a length of silica-based optical fiber. The gratings typically have peak reflectivity of at least 98%. Use of such cavities enables CW pumping of the devices, making the devices suitable for use in optical fiber communication systems. In an exemplary embodiment the device is a Raman amplifier for 1.3 .mu.m signal radiation, and in another exemplary embodiment the device is a Raman laser having an output suitable for pumping an Er-doped fiber amplifier. An exemplary pump radiation source is a laser diode-pumped CW Nd:YAG laser.

Abstract: A compact semiconductor laser light source providing short wavelength (ultraviolet, blue or green) coherent light by means of frequency doubling of red or infrared light from a high power diode heterostructure. The high power diode heterostructure is a MOPA device having a single mode laser oscillator followed by a multimode, preferably flared, optical power amplifier. A tunable configuration having an external rear reflector grating could also be used. A lens could be integrated with the MOPA to laterally collimate the light before it is emitted. Straight or curved, surface emitting gratings could also be incorporated. An astigmatism-correcting lens system having at least one cylindrical lens surface is disposed in the path of the output from the MOPA to provide a beam with substantially equal lateral and transverse beam width dimensions and beam divergence angles. A nonlinear optical crystal or waveguide is placed in the path of the astigmatism-free symmetrized beam to double the frequency of the light.

Abstract: This invention provides an optical converter suitable for use as the gain medium in lasers, optical amplifiers and other optical devices. The converter consists of at least one and preferable two or more optical converter elements which are sandwiched and separated by inactive dielectric layers. An optical pump beam may be passed to the active converter elements through an anti-reflection layer at one surface of the converter and a high reflection mirror may be provided at the opposite side of the converter to reflect the pump beam incident thereon back into the converter for a second pass.

Abstract: A system for providing a single pulse of laser oscillator radiation of broad spectral range operative to excite a plurality of modes of a ring laser operating as an injection locked oscillator. In order to provide injection locking of the ring oscillator at multiple modes, a pump laser for the laser oscillator has its cavity length substantially similar to that of the laser oscillator thereby producing partial mode locking of the laser oscillator by amplitude modulation of the pump laser. In this manner the laser oscillator provides a single pulse of mode rich frequencies which are chosen within the band desired in the ring laser. This pulse continuously circulates within the cavity of the laser oscillator. The output of the laser oscillator through an output mirror thus forms a series of pulses separated in time by the roundtrip delay of the laser oscillator cavity. A single such pulse is selected by Pockels cell gating for injection into the ring oscillator.

Abstract: Separate features of a composite image in a field of view illuminated by a aser beam are respectively monitored by low level optical cavity resonators of an array from which optical data outputs are distributed to high level resonators for optical data correlation. Adjacent low level resonators of the array are coupled by controllers for modal interaction modified by feedback to the controllers from the high level resonators through optical signal transforming means for signal correction purposes in pattern recognition of the composite image.

Abstract: An apparatus and method for flattening the gain of an optical fiber amplifier (18) doped with an ion such as erbium and which is pumped by a pump laser (20). Optical couplers (32, 34) inserted before and after the fiber amplifier couple the main optical path to an optical ring passing through the fiber amplifier so as to form a ring laser. An optical isolator (32) placed in the ring causes the lasing light to only counterpropagate relative to the optical signal being amplified. When the fiber amplifier primarily exhibits inhomogeneous broadening and the ring lases, the lasing light clamps the gain to a value determined by the loop loss, and the value of the clamped gain is relatively uniform across a wide bandwidth.

Abstract: An active monolithic optical device for wavelength division multiplexing (WDM) incorporating diode laser arrays, an output coupling waveguide and a curved Rowland circle based grating to produce a plurality of individual laser beams at slightly different wavelengths is integrated in a common electro-optic material. The wavelength of each laser source is determined by the geometry of the array and the diffraction grating design. The output of all the channels can be collected into a concentrator or lens to be multiplexed in a single output. Applications include a WDM optical amplifier and WDM laser source.

Abstract: Lenses (30', 32') are orthogonally tilted with respect to one another in a telescope to provide imaging for an amplifier-phase conjugate mirror (PCM)(10) in a laser oscillator/amplifier (12). This mutually orthogonal tilting avoids the problem of air breakdown which occurs when the laser energy is otherwise focused at a single point and thus avoids the need to use a vacuum cell to suppress the sparking at the telescope's focus. An adjustment of the tilting of one lens (32') with respect to the other lens (30') also avoids astigmatism.

Abstract: An optical parametric oscillator/laser system includes an optical pump source for generating pump radiation and an embedded dual optical resonator containing an optical parametric oscillator/laser crystal. The embedded dual optical resonator includes a laser resonator and an optical parametric oscillator resonator. The OPOL crystal is an optical parametric oscillator material doped with ions that exhibit lasing transitions. The pump radiation stimulates generation of laser radiation. When the laser radiation reaches the parametric threshold, optical parametric radiation is generated. In one embodiment, the laser resonator and the OPOL resonator are each defined by spaced-apart mirrors. In another embodiment, the OPOL system includes an OPOL rod having end caps at each end. Each end cap includes surfaces for internally reflecting the laser radiation and the parametric optical radiation in a closed loop path so that the OPOL rod and the end caps define an optical resonator.

Abstract: An optical terminal has optical waveguides, 3-dB couplers, laser diodes, laser diodes provided with gratings, and connections on a substrate made of semiconductor material. The grating laser diodes have an external cavity which is formed by the waveguides and delimited by mirrors. Each of the laser diodes has a respective electrical connection through which the diodes can be switched between a light-absorbing mode, a light-amplifying mode, and a light-emitting mode, with the aid of electric current signals, and the diodes are also able to detect a light signal. The terminal can perform a number of functions. A light signal can be received, detected, amplified, and further transmitted. A narrow band light signal of desired wavelength can be generated within a broad wavelength area through the grating diodes in the cavity, and amplified and further transmitted.

Abstract: An arrangement for operation as an optical feedback amplifier which is composed of a DFB laser whose grating selects a wavelength that differs by so much from the wavelength at which the amplification medium has a maximum gain that a constant amplification effect at this beamed-in wavelength is achieved by a progressive quenching of the emission of this wavelength selected by the grating given external optical irradiation via a coupled waveguide of light having a wavelength in the proximity of the wavelength of the gain maximum of the amplification medium.

Abstract: An all-optical, continuous-time, recurrent neural network is disclosed which is capable of executing a broad class of energy-minimizing neural net algorithms. The network is a resonator which contains a saturable, two-beam amplifier; two volume holograms; and a linear, two-beam amplifier. The saturable amplifier permits, through the use of a spatially patterned signal beam, the realization of a two-dimensional optical neuron array; the two volume holograms provide adaptive, global network interconnectivity; and the linear amplifier supplies sufficient resonator gain to permit convergent operation of the network.

Abstract: A semiconductor optical amplifier includes an active region having facets at opposite ends thereof which define an optical cavity having maximum optical gain at a gain peak wavelength .lambda..sub.pk. An antireflection coating on each of the facets has a wavelength .lambda..sub.min of minimum reflectivity that is separated in wavelength from the gain peak wavelength, preferably by about 5 to 30 nanometers. The optical amplifier is operated at a bias current greater than a stimulated emission threshold bias current of the device. The input optical signal has a wavelength at or near the wavelength .lambda..sub.min of minimum reflectivity of the antireflection coatings. The optical amplifier has an electrical bandwidth on the order of 1 to 10 GHz.

Abstract: A tunable dye laser has been found particularly suited to selective photothermolysis. A longer pulse duration which makes the system suitable for a wider range of applications is obtained by modifying the laser to generate a spatially noncoherent beam. The optical system at each end of the laser cell, which may include a lens or spherical mirror, refocuses the aperture of the dye cell near to itself so that substantially all light emanating from the dye cell is returned to the dye cell until the light passes through one of the optic systems as a noncoherent laser beam. A tunable intracavity element tunes the laser across the gain curve of the dye solution. The pulse duration of the laser beam can be selected from a range of durations up to about one millisecond.

Abstract: A compact semiconductor laser light source providing short wavelength (ultraviolet, blue or green) coherent light by means of frequency doubling of red or infrared light from a high power diode heterostructure. The high power diode heterostructure is a MOPA device having a single mode laser oscillator followed by a multimode, preferably flared, optical power amplifier. A tunable configuration having an external rear reflector grating could also be used. A lens could be integrated with the MOPA to laterally collimate the light before it is emitted. Straight or curved, surface emitting gratings could also be incorporated. An astigmatism-correcting lens system having at least one cylindrical lens surface is disposed in the path of the output from the MOPA to provide a beam with substantially equal lateral and transverse beam width dimensions and beam divergence angles. A nonlinear optical crystal or waveguide is placed in the path of the astigmatism-free symmetrized beam to double the frequency of the light.