Abstract: Several embodiments are described for induced electric field or E-field poling of QPM nonlinear crystal materials, such as LiNbO.sub.3, LiTaO.sub.3 and KTP, utilizing approaches which, for the most part, avoid the necessity of depositing or otherwise forming a series of spatially disposed conductive electrodes on one surface of the nonlinear crystal material. E-field poling is accomplished by applying a high voltage electric field in excess, for example, in the range of several kilovolts per cm to several 100 kilovolts per centimeter, at room temperature to provide inverted domains in a pattern of continuously alternating domains corresponding to the regions formed on the first z surface of the crystal. The employment of single, planar-applied liquid electrodes is preferred eliminating any necessity of forming and removing previously formed metal electrodes in the poling process.

Abstract: An improved interferometric modulator permits the reduction in size of optical transmitters. In one embodiment, the optical modulator includes amplifiers or attentuators as phase modulators. In another embodiment, two outputs from a combiner are fed to the modulator, thus avoiding the requirement for an input splitter in the modulator. Light passing through the modulator may be both phase-shifted and amplified or attenuated by optical regulator sections located in the modulator. In another embodiment, the transmitter is included as a multiple-wavelength optical communications source, where individual current sources are provided to actuate a number of light sources feeding into the combiner, a processor controls the operation of each light source, and a modulator driver receives a data input signal to be encoded on the output of the source. By combining a number of modulators, a gray scale modulator may be fabricated for producing a gray scale output, rather than a conventional binary level output.

Abstract: A semiconductor gain medium has an active gain region with a partially patterned radiation diverging region. The partially patterned radiation diverging region may be created with spatial resistive regions formed in a portion of the radiation diverging region having a narrower width than in other portions of the diverging region where the propagating radiation has a greater width. The gain region may be an amplifier or, in addition to the amplifier, may include a resonator cavity, or operate as an unstable resonator.

Abstract: A surface of a compound III-V semiconductor device is passivated and protected, respectively, by treatment with a sulfur-containing or selenium-containing passivation film on the surface followed by the deposit of a GaN, GaP, InGaP, GaAsP, ZnS or ZnSe protection layer. Prior to passivation and deposition of the protective layer, previously formed contact metalizations may be protected with a liftoff film or layer. A low temperature MOCVD process is used to deposit the protection layer so that the integrity of the previously deposited contact metalization is maintained. The preferred range for MOCVD deposition of the protection layer is in the range of about 300.degree. C. to about 450.degree. C. This processing temperature range is within a temperature range where stable contact metalization exists.

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: A vehicle lighting system using individually addressable laser diodes or laser arrays coupled to a fiber optic waveguide. A plurality of laser light sources are grouped together and conveniently located on the vehicle. Each laser light source is individually addressable and produces a beam that is coupled to a fiber optic waveguide. The waveguide distally transmits the beam to various optical loads on the vehicle. Alternatively, each fiber optic waveguide may be coupled to receive a beam from more than one laser light source. This allows switching to an operational light source should one fail. In this manner, the operational life of the system is increased.

Abstract: A semiconductor laser having a light amplifying diode heterostructure body having a single spatial mode aperture region or waveguide and a flared or tapered gain region having a narrow input end and wider output end provided in a resonant cavity, a portion of which cavity may be external of the body. The flared gain region has a narrow aperture end and a wide output end with narrow aperture end optically coupled to a single mode waveguide. A saturable aborbing region is formed as part of the single mode waveguide region and not between it and the flared gain section, and is reverse biased to provide for mode locked operation. The flared gain region and waveguide may be differentially pumped or modulated with current provided by separate contacts, and the flared gain region may be divided into one or more flared gain sections which may be differentially or separately pumped.

Abstract: A wavelength tunable, semiconductor laser includes a gain region, e.g., a flared amplifier region, that permits light propagation with a diverging phase front along at least a portion of the gain region. Optical feedback defines a resonant laser cavity that has a first reflector at a first end of the cavity a second reflector at a second end of the cavity for reflecting at least a portion of the light back propagating in the cavity back into the cavity. Wavelength tuned selection, such as through orientation of a grating reflector or via a prism, is provided in the resonant laser cavity for producing a relatively lower optical loss in the cavity to a selected wavelength or a band of wavelengths of the light propagating within the cavity relative to other nonselected wavelengths such that stable laser oscillation is established at the selected wavelength or band of wavelengths.

Abstract: III-V arsenide-nitride semiconductor crystals, methods for producing such crystals and devices employing such crystals. Group III elements are combined with group V elements, including at least nitrogen and arsenic, in concentrations chosen to lattice match commercially available crystalline substrates. Epitaxial growth of these III-V crystals results in direct bandgap materials, which can be used in applications such as light emitting diodes and lasers. Varying the concentrations of the elements in the III-V crystals varies the bandgaps, such that materials emitting light spanning the visible spectra, as well as mid-IR and near-UV emitters, can be created. Conversely, such material can be used to create devices that acquire light and convert the light to electricity, for applications such as full color photodetectors and solar energy collectors.

Abstract: An upconversion fiber laser uses a pump source which may be another fiber laser, such as a high power, diode-laser-pumped, fiber laser. The upconversion fiber laser includes an optical fiber whose core region is doped with an active lasing ionic species capable when optically pumped of undergoing upconversion excitation, such as certain rare earth ionic species, and which is embedded in a cladding of the optical fiber. Use of a fiber pump laser can improve coupling of pump light into the optical fiber, thereby achieving higher pump intensities in the core region and improved upconversion efficiency. The upconversion fiber laser's resonant laser cavity is defined by feedback means which can include at least one reflective grating formed in the optical fiber, as well as a reflective end face of the optical fiber.

Abstract: In an optical transmission medium, such as a fiber amplifier, two optically distinguishable signals with complementary modulation are both inputted into the amplifying medium for encoding information, particularly a serial stream of digital data, or alternatively, redundant encoding of pulses. The gain profile in the medium is preferably maintained approximately constant at all times, so that whichever amplified signal is used as the primary information carrier, its output intensity will be substantially stable from pulse to pulse, independent of recent pulse history. The two complementary signals may have different orthogonal linear polarizations or wavelengths with the same stimulated emission cross-section, so that the population inversion profile stays constant, whichever signal happens to be on at a given moment.

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 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: A fiber laser or amplifier in which the optical fiber gain medium has two or more nonconcentric core regions, each of which is capable of gain or lasing when optically pumped. The fiber may be single clad or double clad, with multiple core regions embedded within a common cladding region or within separate cladding regions. The core regions may be arranged in a linear, closely spaced hexagonal, rectangular matrix or some other configuration and positioned symmetrically or noncentrosymmetrically, centered or off-center within the core region or regions. The spacing between neighboring core regions may be far enough apart to minimize optical interaction between cores for independent light amplifying or laser action or be close enough for phase-locked operation of the multiple cores to occur. The cores may be doped with the same or different active ionic species, of which one or more could be upconverting ions.

Abstract: A semiconductor laser that includes a monolithic submount with a light emitting source aligned along one side thereby defining a radiation path over which the emitted light propagates. The submount includes two notches that flank the light emitting source. A micro-lens is mounted adjacent to the light emitting source by attaching to the submount with either epoxy or solder. Finally, the components of the semiconductor laser have matching coefficients of thermal expansion so that the optical alignment of the light emitting source and the micro-lens is maintained notwithstanding thermal cycling.

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 cooling device formed in a thermally conductive substrate having a microstructure, such as a plurality of thermally conductive posts spaced apart by dimensions that induce capillary action in a liquid coolant. The posts extend away from the heated region and a space between the posts is supplied with liquid coolant which is contained by a meniscus near the tips of the posts. The coolant vaporizes at the meniscus and absorbs heat but, due to increased pressure in the coolant contained by the meniscus, does not boil within the space between the posts, allowing more liquid coolant contact with the thermally conductive substrate and posts. The vaporized coolant may be discharged into the air or into a chamber adjoining the tips having a lower pressure for removal of additional heat by gaseous expansion. The discharge of gaseous coolant allows the capillary flow of the liquid coolant in the space to be unimpeded, and the flow of liquid coolant may be augmented by a fluid pump.