Abstract: Adiabatic mode control and structural reproducibility are achieved by a tapered semiconductor waveguide structure wherein semiconductor guiding layers are interleaved with stop-etch layers and each guiding layer extends further along the propagation axis of the waveguide further than the guiding layer immediately adjacent thereabove to create a staircase-like core or guiding structure. Cladding regions of appropriate semiconductor material having a lower index of refraction than the tapered core structure may be added to completely surround the tapered guiding structure. The profile of the tapered structure is realizable as any desired staircase-like shape such as linear, parabolic, exponential or the like. Additional layers of higher index of refraction semiconductor material may be included in the cladding region to permit additional beam shaping of the expanded spatial mode propagating along the tapered waveguide.

Abstract: Combinatorial (Boolean) logic functions are provided by ultrafast optical logic devices which utilize soliton trapping between two optical signals propagating in a birefringent fiber. The logic devices are three terminal devices having orthogonally polarized soliton input signals and a single output signal. Optically filtering the output from the fiber permits the desired combinatorial logic operation to be performed on the input optical signals. Logic operations include AND, exclusive-OR, NOT, and NOR functions. In operation, the devices exhibit phase insensitivity, low switching energy, high contrast ratio between output logic levels, and cascadability. In one embodiment of the invention, a first optical signal and a second optical signal are optically coupled into the principal axes of a birefringent fiber.

Abstract: A vacuum photodetector has been fabricated in a coplanar microstrip transmission line geometry to achieve high quantum efficiency and picosecond response time. The coplanar microstrip transmission lines, photocathode and anode, are mounted on an insulating substrate such as sapphire and are electrically biased with respect to each other. Photodetection occurs by classical photoelectric emission as a result of impinging photon energies exceeding the work function of the photocathode.

Abstract: Adiabatic mode control and structural reproducibility are achieved by a tapered semiconductor waveguide structure wherein semiconductor guiding layers are interleaved with stop-etch layers and each successive guiding layer extends further along the propagation axis of the waveguide than the guiding layer immediately adjacent thereabove to create a staircase-like core or guiding structure. Cladding regions of appropriate semiconductor material having a lower index of refraction than the tapered core structure may be added to completely surround the tapered guiding structure. The profile of the tapered structure is realizable as any desired staircase-like shape such as linear, parabolic, exponential or the like. Additional layers of higher index of refraction semiconductor material may be included in the cladding region to permit additional beam shaping of the expanded spatial mode propagating along the tapered waveguide.

Abstract: Frequency stabilization of a long wavelength semiconductor laser is achieved by employing the optogalvanic effect in a feedback control loop with the laser. Absolute references are obtained using noble gases such as argon (1.2 .mu.m to 1.4 .mu.m) and krypton (1.4 .mu.m to 1.6 .mu.m). Standard detection, feedback control and dithering lock-in techniques are used to insure proper frequency stabilization.

Abstract: An optical device is disclosed wherein a Fabry-Perot etalon (12) is used as a spectral mode selector externally coupled to a source of modelocked optical pulses (10). By adjusting the cavity length of the etalon (12), a plurality of equally spaced predetermined modes output from the source are transmitted by the etalon. These modes which are transmitted combine coherently to create a stream of optical pulses (16) having a higher repetition rate than the repetition rate of the source.

Abstract: Heterodyne and homodyne lightwave communication systems require transmitter optical sources and receiver local oscillators to be locked to a particular frequency. In accordance with the present invention, each transmitter laser and each receiver local oscillator laser is independently and locally stabilized to the same absolute frequency standard using species exhibiting atomic or molecular absorption lines in the wavelength range of interest. Frequency stabilization of the lasers is achieved by employing an optogalvanic effect element in a feedback control loop with the laser. Absolute frequency standards are obtained using gas discharge tubes containing, for example, noble gases such as argon (1.2 .mu.m to 1.4 .mu.m) and krypton (1.4 .mu.m to 1.6 .mu.m) and the like. Standard synchronous detection and feedback control techniques are used to insure proper long-term frequency stability.

Abstract: To overcome the deleterious effects of the nonuniform frequency modulation response in semiconductor lasers due to current injection in direct frequency modulation applications, it has been determined that the linewidth enhancement factor .alpha. be made as large as possible. In one embodiment, distributed feedback lasers well suited for frequency modulation lightwave communication systems are designed to have an integrated feedback element such as a corrugation grating whose effective pitch is selected to cause the Bragg wavelength and, therefore, the laser operating wavelength to be longer than the wavelength at substantially the maximum gain or gain peak in the semiconductor structure without the grating. That is, the wavelength of the grating is effectively detuned toward the longer wavelength and lower energy side of the peak of the gain profile.

Abstract: Combinatorial (Boolean ) logical functions are provided in a programmable optical logic device by combining a symmetric self-electrooptic effect device (S-SEED) with a logic control element for optically programming the S-SEED to initiate logic operations in a predetermined mode. A predetermined reference threshold optical signal is applied to one input of the S-SEED while first and second optical data signals are jointly applied to another input of the S-SEED to permit the desired combinatorial logic operation to be performed on the optical data signals by the optical logic device. As such, the programmable optical logic device is said to perform threshold logic operations. Logic operations which may be programmed into the optical logic device include AND, OR and NOT functions. A single optical signal is provided as output from each optical logic device.

Abstract: To overcome the deleterious effects of the nonuniform frequency modulation response in semiconductor lasers due to current injection in direct frequency modulation applications, it has been determined that the linewidth enhancement factor .alpha. be made as large as possible. In one embodiment, distributed Bragg relector lasers well suited for frequency modulation lightwave communication systems are designed to have an integrated feedback element such as a corrugation grating whose effective pitch is selected to cause the Bragg wavelength and, therefore, the laser operating wavelength to be longer than the wavelength at substantially the maximum gain or gain peak in the semiconductor structure. That is, the wavelength of the grating is effectively detuned toward the longer wavelength and lower energy side of the peak of the gain profile.

Abstract: Lower switching energies, enhanced electroabsorption and reduced tolerances on the operating wavelength of incident light are achieved while contrast between low and high absorption states is maintained in accordance with the principles of the invention by a self electrooptic device including an intrinsic quantum well region having an asymmetric electronic characteristic across a narrow bandgap subregion between the two wide bandgap layers defining the quantum well region. As a result, the quantum well region polarizes electrons and holes within the subregion in an opposite direction relative to a direction for an electric field applied to the device. The asymmetric electronic characteristic is realized as a compositionally graded, narrow bandgap layer or as a pair of coupled narrow bandgap layers of differing thicknesses separated by a thin wide bandgap layer.

Abstract: Biological particles are successfully trapped in a single-beam gradient force trap using an infrared laser. The high numerical aperture lens objective in the trap is also used for simultaneous viewing.Several modes of trapping operation are presented.

Abstract: In an optoelectronic integrated circuit, an electronic device is integrated with an optical device by fabricating the electronic device directly in a doped semiconductor layer of the optical device. The optical devices contemplated for use include at least a region of multiple low-doped or intrinsic quantum well layers; electronic devices include bipolar and field-effect transistors. Resulting integrated circuits exhibit a high degree of planarity.

Abstract: An optical fiber communications system with Raman amplification of the signal radiation comprises a broadband pump radiation source, or, preferably, a multiplicity of pump radiation sources and polarization maintaining optical fiber as the transmission medium. The sources are selected to result in a pump radiation spectrum having individual spectral components such that pump radiation intensity for each spectral component in the desired polarization in the fiber core is less than a critical intensity I.sub.c. In particular, the average intensity of pump radiation in a first spectral interval, centered on any wavelength .lambda..sub.p in the pump radiation spectrum and of width equal to the Brillouin line width of the fiber at .lambda..sub.p, is to be less than that average intensity in the first spectral interval that results in conversion of 10% of the radiation in the first spectral interval to stimulated Brillouin radiation.

Abstract: A bidirectional optical communications system is described using a multiple quantum well structure as both a photodetector and light modulator.

Abstract: Crosstalk for a directional coupler switch employing a reversed .DELTA..beta. electrode structure is reduced to a minimum by properly placing electrode sections over the waveguides to compensate interwaveguide coupling preceding an electrode section with interwaveguide coupling following the electrode section.

Abstract: Semi-insulating epitaxial layers of Group III-V based semiconductor compounds are produced by a MOCVD process through the use of organic titanium-based compounds. Resistivities greater than 1.times.10.sup.7 ohm/cm have been achieved.

Abstract: A process for creating bipolar and CMOS transistors on a p-type silicon substrate is disclosed. The silicon substrate has typical n+ buried wells and field oxide regions to isolate the individual transistor devices. In accordance with the process, stacks of material are created over the gate elements of the CMOS devices and over the emitter elements of the bipolar transistors. The stacks of material over the gate elements have a silicon dioxide gate layer in contact with the epitaxial layer of the substrate, and the stacks of material over the emitter elements have a polycrystalline silicon layer in contact with the epitaxial layer. Walls of silicon dioxide are created around the stacks in order to insulate the material within the stacks from the material deposited outside of the walls. Polycrystalline silicon in contact with the epitaxial layer is deposited outside the walls surrounding the stacks.

Abstract: Information borne by an optical signal at a first wavelength is transferred intact to another optical signal at a second wavelength and vice versa via an optoelectronic circuit employing quantum well devices connected serially to facilitate self electrooptic effects therein. The optoelectronic circuit accepts two input signals and provides two output signals wherein an input signal and its corresponding output signal are at the same wavelength. Bidirectional information transfer with bidirectional wavelength conversion is permitted by the optoelectronic circuit.

Abstract: The invention is a nonlinear or bistable optical device having a low switching energy. The invention uses a means responsive to light for generating a photocurrent, a structure having a semiconductor quantum well region, and means responsive to the photocurrent for electrically controlling an optical absorption of the semiconductor quantum well region. The optical absorption of the semiconductor quantum well region varies in response to variations in the photocurrent. A photodiode or phototransistor may be used as the means responsive to light, and may be made integral with the structure having the semiconductor quantum well region. An array of devices may be fabricated on a single chip for parallel logic processing.