Abstract: A semiconductor light amplifying medium has reduced self-focusing and optical filamentation for providing higher power coherent outputs in broad-area laser and amplifier devices. In one embodiment, a longitudinally inhomogeneous active region has alternating segments of first gain portions and second compensating portions. The compensating portions have a negative self-focusing parameter [.differential.n/.differential.P] and may be light absorbing (negative gain) regions with negative antiguiding factor .alpha. or light amplifying (positive gain) regions with positive antiguiding factor .alpha.. The .alpha.-parameter is defined as the ratio of refractive index change per change in gain, as a function of carrier density. In a second embodiment, the medium may have longitudinally varying peak filament period so that filaments beginning to form in one portion of the active region are subsequently dispersed in a succeeding portion, slowing filament growth.

Abstract: A method for providing an nonlinear, frequency converting optical QPM waveguide device by growing a first ferroelectric oxide film or layer on a second ferroelectric layer or medium wherein, in first and second embodiments, respectively, the second layer is initially provided with a periodic nonlinear coefficient pattern or a periodic pattern comprising a seed layer. During the growth of the first layer, the periodic pattern formed in the second layer, is replicated, transformed or induced into the first layer resulting in a plurality of substantially rectangular prismatic-shaped domains in the first layer having the periodic nonlinear coefficient pattern status based upon the periodic patterning of the second layer.

Abstract: A wavelength-stabilized, semiconductor laser having a light amplifying diode heterostructure with a flared gain region in an external resonant cavity. The flared gain region has a narrow aperture end which may be coupled to a single mode waveguide and a wide output end. A light emitting surface of the heterostructure proximate to the Wide end of the flared gain region is partially reflective and combines with an external reflector to form a resonant cavity that is effectively unstable. The intracavity light-emitting surface proximate to the narrow aperture end is antireflection coated. The external reflector may be a planar mirror or a grating reflector. A lens or an optical fiber may couple the aperture end of the flared gain region to the external reflector. Frequency-selective feedback is provided by orienting the grating reflector or providing a prism in the cavity in front of the external planar mirror. Other filtering elements may also be placed in the external cavity.

Abstract: A harmonic generator laser system which features a distributed Bragg reflector (DBR) or distributed feedback (DFB) tunable diode laser coupled to a quasi-phasematched (QPM) waveguide of optically nonlinear material. Tuning of the DBR laser may be achieved either thermally or via current injection, or both, halving the wavelength of a red laser into the visible blue spectral band. Thermal tuning may provide a coarse tuning adjustment, while injected current may provide fine tuning accessible to a user. Separately or in combination with current tuning, a modulation signal may be applied to the DBR laser for achieving an intensity modulated or a pulsed output. In another embodiment, modulation may be achieved by frequency modulation of the laser. A very compact tunable blue laser is formed. In yet another embodiment a double clad fiber amplifier is disposed between the tunable laser and the waveguide.

Abstract: A semiconductor laser having a light amplifying diode heterostructure with a flared gain region in an external resonant cavity. The flared gain region has a narrow aperture end which may be coupled to a single mode waveguide and a wide output end. A light emitting surface of the heterostructure proximate to the wide end of the flared gain region is partially reflective and combines with an external reflector to form a resonant cavity that is effectively unstable. The intracavity light-emitting surface proximate to the narrow aperture end is antireflection coated. The external reflector may be a planar mirror or a grating reflector. A lens or an optical fiber may couple the aperture end of the flared gain region to the external reflector. Frequency-selective feedback is provided by orienting the grating reflector or providing a prism in the cavity in front of the external planar mirror. Other filtering elements may also be placed in the external cavity.

Abstract: A semiconductor laser having a light amplifying diode heterostructure with a flared gain region in an external resonant cavity. The flared gain region has a narrow aperture end which may be coupled to a single mode waveguide and a wide output end. A light emitting surface of the heterostructure proximate to the wide end of the flared gain region is partially reflective and combines with an external reflector to form a resonant cavity that is effectively unstable. The intracavity light-emitting surface proximate to the narrow aperture end is antireflection coated. The external reflector may be a planar mirror or a grating reflector. A lens or an optical fiber may couple the aperture end of the flared gain region to the external reflector. Frequency-selective feedback is provided by orienting the grating reflector or providing a prism in the cavity in front of the external planar mirror. Other filtering elements may also be placed in the external cavity.

Abstract: An optical system and method for detecting the presence and location of multiple objects in a field. The optical system has at least one light source to generate a beam, which beam is scanned by at least one first reflecting surface to generate at least three sets of beams. A first and second set of beams are overlapped across the field by at least one second reflecting surface and a third set overlaps the field without the second reflecting surface. The beam intensity is measured by at least one detection means.

Abstract: An optical amplifier semiconductor device which is differentially pumped and a master oscillator power amplifier (MOPA) device employing such an amplifier. The amplifier allows the light propagating therein to diverge along at least part of its length, and may be a flared amplifier having a gain region that increases in width toward its output at a rate that equals or exceeds the divergence of the light. The amplifier is pumped with a current density at its input end which is smaller than the current density used to pump the output end for maintaining coherence of the beam to high power levels. Differential pumping may be both longitudinal and lateral within the amplifier. A single mode preamplifier section may be optically coupled to the input end of the amplifier. The amplifier input may have a width which is the same as or wider than that of the preamplifier output. The preamplifier may have a constant mode width or may be tapered to alter the divergence of the beams provided to the amplifier section.

Abstract: A wavelength-stabilized, semiconductor laser having a light amplifying diode heterostructure with a flared gain region in an external resonant cavity. The flared gain region has a narrow aperture end which may be coupled to a single mode waveguide and a wide output end. A light emitting surface of the heterostructure proximate to the wide end of the flared gain region is partially reflective and combines with an external reflector to form a resonant cavity that is effectively unstable. The intracavity light-emitting surface proximate to the narrow aperture end is antireflection coated. The external reflector may be a planar mirror or a grating reflector. A lens or an optical fiber may couple the aperture end of the flared gain region to the external reflector. Frequency-selective feedback is provided by orienting the grating reflector or providing a prism in the cavity in front of the external planar mirror. Other filtering elements may also be placed in the external cavity.

Abstract: An upconversion fiber laser with a double-clad fiber is pumped with a laser-diode-based laser pump source, the inner cladding of the fiber forming a low transmission loss waveguide for the pump light. The central core of the fiber is doped with an active lasing ionic species capable of undergoing upconversion excitation, such as certain rare earth ionic species. The use of a double-clad fiber permits the use of high power, high brightness laser diodes, including those with broad emitting apertures, as well as high power diode laser pumped fiber lasers, as the pump source, thereby achieving higher pump intensities within the upconversion laser fiber and improved upconversion efficiency. Pump brightness can be further increased with multiple pump schemes which use multiple pump wavelengths in different absorption bands, multiple pump wavelengths within the same absorption band, pump light from pairs of cross-polarized sources, and pumping from both ends of the fiber.

Abstract: A semiconductor laser having a light amplifying diode heterostructure with a flared gain region in an external resonant cavity. The flared gain region has a narrow aperture end which may be coupled to a single mode waveguide and a wide output end. A light emitting surface of the heterostructure proximate to the wide end of the flared gain region is partially reflective and combines with an external reflector to form a resonant cavity that is effectively unstable. The intracavity light-emitting surface proximate to the narrow aperture end is antireflection coated. The external reflector may be a planar mirror or a grating reflector. A lens or an optical fiber may couple the aperture end of the flared gain region to the external reflector. Frequency-selective feedback is provided by orienting the grating reflector or providing a prism in the cavity in front of the external planar mirror. Other filtering elements may also be placed in the external cavity.

Abstract: An optical system and method for detecting the presence and location of at least one stationary or moving object in a field. The optical system has at least one light source to generate a beam, which beam is scanned by at least one first reflecting surface to generate a plurality of beams. The beams are overlapped across the field by at least one second reflecting surface and their intensity is measured by at least one detection means.

Abstract: A phased array of flared amplifiers fed by phase adjusters and a power splitter produces a single high power beam when the flared amplifier sections are aligned and closely spaced. In one embodiment the array is excited by a DBR laser integrated into the same substrate as the flared amplifiers. In another embodiment the array is self-excited and forms a laser between an edge of the substrate common to the power splitter and an edge of the substrate common to the flared amplifier.

Abstract: A semiconductor laser having a light amplifying diode heterostructure with a flared gain region in an external resonant cavity. The flared gain region has a narrow aperture end which may be coupled to a single mode waveguide and a wide output end. A light emitting surface of the heterostructure proximate to the wide end of the flared gain region is partially reflective and combines with an external reflector to form a resonant cavity that is effectively unstable. The intracavity light-emitting surface proximate to the narrow aperture end is antireflection coated. The external reflector may be a planar mirror or a grating reflector. A lens or an optical fiber may couple the aperture end of the flared gain region to the external reflector. Frequency-selective feedback is provided by orienting the grating reflector or providing a prism in the cavity in front of the external planar mirror. Other filtering elements may also be placed in the external cavity.

Abstract: A monolithic multi-wavelength laser diode array having a composite active region of at least two dissimilar quantum well layers that are partially mixed in at least one of their constituent atomic species in at least one area of the active region. Different areas of the active region are characterized by different emission wavelengths determined by the degree of intermixing. An impurity free interdiffusion, such as vacancy enhanced interdiffusion, is used to provide the intermixing. Each area may have one or more waveguides and distributed Bragg reflector gratings tuned to the emission wavelength of the corresponding area of the active region. Each area or waveguide may also be separately pumped with an individually addressable current injection electrode. The laser output may be coupled into a ferroelectric frequency doubler integrally formed on the array substrate.

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: A semiconductor laser includes a grating that is disposed at an angle to cavity reflectors to coherently diffract a beam of light along a path that is at least partially laterally directed within the cavity. The grating period and orientation are selected such that a specified wavelength of the light beam propagating along the path will resonate for light that impinges upon the end reflectors at normal incidence. By keeping the angle of incidence of the light beam upon the grating greater than about 45 degrees, reflectivity of the grating is maximized and the required grating period is larger thereby simplifying the fabrication of the grating.

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: An optical amplifier with at least one high reflectivity facet oriented at a nonperpendicular angle to the amplifier's waveguide to couple light vertically through a top or bottom surface of the amplifier. Angled facets could be at just one end of the waveguide or at both ends of the waveguide. In the latter case, the facets can be approximately parallel to or perpendicular to each other for respective coupling to opposite or same sides of the amplifier. Multiple amplifiers can be formed end-to-and with v-grooves defining the angled facets or can be formed side-by-side with parallel waveguides. Waveguides can also branch to form a 1:2, 1:4 or 2:2 optical signal multiplier or optical switch depending on whether just one or all of the waveguide branches are electrically pumped. Fibers are coupled to the amplifier receiving and emitting surfaces. Angling the fiber end with respect to the surface prevents reflections from feeding back into the amplifier waveguide.

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.