Abstract: The present invention relates to a method for synthesizing supergratings using Fourier analysis. The method divides the synthesis process into two stages: synthesis of an “analog” grating profile, followed by a quantization step. The method provides a generalized procedure for analog synthesis by drawing on the Fourier approximation and on finite-inpulse-response (FIR) filter design theory, while it interprets the simple threshold quantization as a “zeroth order” Delta-Sigma Modulator, which it improves.

Abstract: A method of producing Y-junction carbon nanotubes. An alumina template with branched growth channels is produced after which individual Y-junction carbon nanotubes are grown directly by pyrolysis of acetylene using cobalt catalysis. The use of a branched growth channel allows the natural simultaneous formation of a very large number of individual but well-aligned three-port Y-junction carbon nanotubes with excellent uniformity and control over the length (up to several tens &mgr;m) and diameter (15-100 nm) of the “stem” and “branches” separately. These Y-junctions offer the nanoelectronics community a new base material for molecular scale electronic devices including for example transistors and rectifiers.

Abstract: The present invention provides self-collimating multiwavelength lasers (MWL) including a planar gain medium with a resonance cavity defined by superimposed gratings. These laser devices are characterized by lasing wavelengths with multiple peaks in their reflectance spectra defined by the superimposed gratings. The gratings also limit beam divergence, producing self-collimated multiwavelength output, with the potential for high power. These devices can be implemented in any planar gain medium in which multi-peak gratings can be produced, including but not limited to semiconductors and doped glasses. The self-collimated MWL's disclosed herein have applications in areas such as DWDM (dense wavelength division multiplexing) communications systems, free-space uses such as interconnects, range-finding, and inter-satellite infrared communication.

Abstract: A superimposed grating tunable WDM semiconductor laser is provided comprising a grating structure is a binary superimposed grating comprising a plurality of segments of equal dimension, s, each segment having one of two values of refractive index, whereby the grating structure is provided by a binary modulation of the refractive index modulation of segments s along the length of the grating.Thus, for a superimposed grating structure for an optoelectronic device for providing a spectrum comprising j reflection peaks at wavelengths .lambda..sub.j, the grating comprising a binary superimposed grating (BSG) having a sequence of a plurality of segments of equal size s, each segment of the sequence having a refractive index of one of two values wherein the effective waveguide index of the ith segment n.sub.i.sup.0 (.lambda.) is allowed to be changed by .DELTA.n.multidot.(m-1/2) with m=1 or m=0: ##EQU1## where i=1,2,3 . . . is the segment number, for digital position i.multidot.s, n.sup.0 (.lambda.

Abstract: A grating-in-etalon wavelength division multiplexing device is disclosed. In one aspect the device includes an etalon structure with a single volume (or Bragg) diffraction grating, multiple superimposed volume diffraction gratings or a binary volume supergrating is interposed between the reflective opposed faces of the etalon. The etalon includes a tilt mechanism for tilting one or both of the reflective faces at a preselected angle with respect to each other from the parallel. A multiple wavelength light beam is directed through the volume grating in different preselected directions so that light of wavelengths satisfying the Bragg condition on each traversal of the grating is diffracted in a direction different from the direction of the incident beam. The diffracted beam exits the etalon and is wavelength interrogated in a detector while the undiffracted wavelengths propagate through the grating to be reflected from the opposed mirror face back through the volume grating.

Abstract: A semiconductor laser device is provided in which an active layer is sandwiched between and upper and lower cladding layer, the lower cladding layer being situated on a semi-insulating substrate. The upper cladding layer includes a raised ridge section running from end to end between the facets or end surfaces of the laser cavity. The ridge section aids in optical confinement. A p+ contact region and an n+ contact region are formed extending though the upper cladding layer, the active region and the lower cladding layer on both sides of the ridge to provide lateral injection of charge carriers into the active region of the laser.

Abstract: A semiconductor laser device having a body with opposed facets and including an active region with aluminum diffused into the active region along the facets thereof. Adding aluminum to the portions of the active region along the facets increases the bandgap of the active region along the facets and provides a semiconductor laser device having an increased catastrophic optical damage (COD) level. The semiconductor laser device is produced by depositing a thin film of aluminum on the facets of the semiconductor laser device and then heat treating to cause diffusion of the aluminum film or phosphorus into the body of the semiconductor laser device along the facets thereof, thereby changing the composition of the semiconductor laser device body along the facets. Alternatively, phosphorus may be diffused into the body of the semiconductor laser device along the facets thereof.

Abstract: There is provided a semiconductor laser device capable of emitting a laser beam having stable transverse modes. A ridge type semiconductor laser device comprises an upper clad layer 15 left on its active layer to a thickness (d) between 0.25 and 0.50 m in order to ensure a stable production of fundamental transverse modes for laser operation and a rib-shaped clad layer 16 having a bottom width (W) between 2.0 .mu.m and 3.5 .mu.m and projecting from the upper clad layer in juxtaposition with the light emitting region of the active layer 13. When d and W are found within the respective ranges, the device emits a laser beam having stable transverse modes.

Abstract: A three terminal semiconductor device relies on resonant tunnelling through a quantum well resonator for its operation. The device has a first layer of a narrow bandgap semiconductor, a second layer of a narrow bandgap semiconductor, and a quantum well resonator between the first layer of a narrow bandgap semiconductor and the second layer of a narrow bandgap semiconductor. The quantum well resonator comprises a first layer of a wide bandgap semiconductor, a second layer of a wide bandgap semiconductor, and a third layer of a narrow bandgap semiconductor between the first layer of a wide bandgap semiconductor and the second layer of a wide bandgap semiconductor. All of the layers referred to above have a common conductivity polarity.

Abstract: Improved p-channel FETs and optoelectronic device make use of reduced hole effective mass achieved with quantum confinement. The devices include multiple one-dimensional p-channel FETs which have electrically induced and controllable one dimensional p-type semiconductor wires; square well two-dimensional p-channel FETs; and laser diodes and light emitting diodes which use one dimensional p-type semiconductor wires.

Abstract: A Metal-Semiconductor-Metal (MSM) photodetector comprises a semiconductor substrate, a semiconductor barrier layer on the substrate, a thin semiconductor active layer on the barrier layer, and at least two electrical contacts to the active layer. The barrier layer prevents carriers generated deep in the substrate from reaching the contacts. As it is the delayed detection of these carriers which limits the useful operating speed or bandwidth of conventional MSM photodetectors, the MSM photodetector according to the invention is capable of higher speed operation than conventional MSM photodetectors.

Abstract: A logic gate comprises a bipolar switching transistor and a depletion mode field effect load device. A current independent voltage source and a voltage independent current source are connected in series between an input terminal of the logic gate and a base of the bipolar transistor. The voltage independent current source is a depletion mode field effect transistor having a source and drain which are connected in series with the current independent voltage source and the base of the bipolar transistor. A feedback device is connected in series between a gate of the current source field effect transistor and a gate of the load transistor. A discharge device is connected in parallel with the current independent voltage source for actively discharging a base-emitter junction of the bipolar transistor during switching of the bipolar transistor from an on state to an off state. The logic gate is particularly suitable for use in memory elements.

Abstract: A hot electron transistor includes two base regions between the emitter and collector, with the first and second bases separated by a base-base barrier. The emitter injects high energy electrons across an emitter barrier into the first base, which acts as an electron gun to focus and accelerate the electrons and inject them across the base-base barrier into the second base. An input signal is applied to the second base, to modulate the flow of electrons from the second base across a collector barrier and into the collector.

Abstract: Improved p-channel FETs and optoelectronic devices make use of reduced hole effective mass achieved with quantum confinement. The devices include multiple one-dimensional p-channel FETs which have electrically induced and controllable one dimensional p-type semiconductor wires; square well two-dimensional p-channel FETs; and laser diodes and light emitting diodes which use one dimensional p-type semiconductor wires.

Abstract: A bipolar transistor has a barrier layer interposed between its base and its emitter. The barrier layer is formed of a different, wider band gap, semiconductor material than the base and the emitter and has the same conductivity type as the emitter. The barrier layer exhibits a large difference in the effective electron mass and the effective whole mass, and presents a small barrier to majority carriers. The tunneling emitter bipolar transistor exhibits a comparable current gain while having better temperature stability, less light sensitivity, and a much lower emitter resistance (leading to a much higher cut-off frequency) than conventional heterojunction bipolar transistors.