Abstract: A recombination layer with a gradient work function is provided which increases the power-conversion efficiency of multijunction photovoltaic devices by reducing the energy barrier to charge carriers migrating between pairs of photovoltaic junctions thereby facilitating the optimal recombination of opposing electron and hole currents generated when the photovoltaic is illuminated.

Abstract: Contemplated methods and devices comprise performing electrochemical sample analysis in a multiplexed electrochemical detector having reduced electrical cross-talk. The electrochemical detector includes electrodes that share a common lead from a plurality of leads. The sample, which may be a liquid sample, is introduced into one or more sample wells and a signal is applied to at least one of the electrodes. A response signal is measured while simultaneously applying a substantially fixed potential to each of a remainder of the plurality of leads.

Abstract: The invention provides a new class of photoconductive materials and devices, and methods for obtaining high internal photoconductive gain. The devices include a semiconductor or material with an electronic band gap provided in a confined geometry and which exhibits multi-exciton generation (MEG) when illuminated with photons with energies above the threshold for MEG. Due to carrier-carrier Coulombic interactions, multi-excitons within the confined material efficiently recombine via Auger recombination, in which a carrier from one exciton is excited to a higher energy level relative to the band edge. Carriers excited by Auger recombination are subsequently trapped by trap states that capture carriers excited high above the band edge more efficiently than carriers near the band edge. Carriers trapped by the trap states allow for the collection and recirculation of untrapped carriers of opposite charge when used as a photoconductive device, producing high internal photoconductive gain.

Abstract: A recombination layer with a gradient work function is provided which increases the power-conversion efficiency of multijunction photovoltaic devices by reducing the energy barrier to charge carriers migrating between pairs of photovoltaic junctions thereby facilitating the optimal recombination of opposing electron and hole currents generated when the photovoltaic is illuminated.

Abstract: Photovoltaic cells are fabricated in which the compositions of the light-absorbing layer and the electron-accepting layer are selected such that at least one side of the junction between these two layers is substantially depleted of charge carriers, i.e., both free electrons and free holes, in the absence of solar illumination. In further aspects of the invention, the light-absorbing layer is comprised of dual-shell passivated quantum dots, each having a quantum dot core with surface anions, an inner shell containing cations to passivate the core surface anions, and an outer shell to passivate the inner shell anions and anions on the core surface.

Abstract: The invention provides a new class of photoconductive materials and devices, and methods for obtaining high internal photoconductive gain. The devices include a semiconductor or material with an electronic band gap provided in a confined geometry and which exhibits multi-exciton generation (MEG) when illuminated with photons with energies above the threshold for MEG. Due to carrier-carrier Coulombic interactions, multi-excitons within the confined material efficiently recombine via Auger recombination, in which a carrier from one exciton is excited to a higher energy level relative to the band edge. Carriers excited by Auger recombination are subsequently trapped by trap states that capture carriers excited high above the band edge more efficiently than carriers near the band edge. Carriers trapped by the trap states allow for the collection and recirculation of untrapped carriers of opposite charge when used as a photoconductive device, producing high internal photoconductive gain.

Abstract: A bidirectional transceiver assembly includes a VCSEL structure that emits light at a defined wavelength on a substrate structure. A photodetector receives the light. A hole structure is formed on the substrate structure to allow the light from the VCSEL structure to be emitted so as to form an optical path.

Abstract: An entirely passive all-optical device, referred to as an optical hard limiter, includes alternating layers of materials having oppositely signed Kerr coefficients and substantially different linear indices of refraction, wherein the higher linear index material has the negative Kerr coefficient and the lower index material has the positive Kerr coefficient. The optical device has two distinct transmittance curves. Various optical devices and systems can be built from such optical hard limiters.

Abstract: A wavelength selective switch device is disclosed that includes an elongated signal communication path extending from a first end of the device to a second end of the device. The signal communication path extends through a plurality of regions of varying indices of refraction, and the plurality of regions includes adjustable regions that are each coupled to an adjustable voltage source for changing a voltage potential across each of the adjustable regions such that the index of refraction of said adjustable regions may be changed by changing the voltage potential across each adjustable region.

Abstract: An optical amplifier has a spatially varying absorption spectrum formed in a monolithic InGaAsP structure whose quantum well active structure has modified effective bandgap properties. The effective bandgap properties can be modified by rapid thermal annealing to cause the diffusion of defects from one or two InP defect layers into the quantum well active structure. Multiple such optical amplifiers, having their effective bandgap properties modified to provide different gain spectra, can be monolithically formed in a single semiconductor structure for broadband amplification, in which case their individual gain spectra can be controlled to control the total gain spectrum dynamically. Alternatively, the optical amplifier can be used in a Mach-Zehnder wavelength converter for broadband wavelength conversion.

Abstract: Method of synthesis of confined colloidal crystals using electrodeposition. The present invention provides a method of growing confined colloidal crystal structures using electrodeposition of monodispersed charged colloid spheres onto a substrate patterned with an array of electroconductive surface relief features on a surface of a substrate. In this approach, control over large-scale ordering is achieved via a planar pattern whose scale is on the order of tens of microns, a regime readily accessed through coarse lithography, laser micromachining, and holography.

Abstract: Method of synthesis of confined colloidal crystals using electrodeposition. The present invention provides a method of growing confined colloidal crystal structures using electrodeposition of monodispersed charged colloid spheres onto a substrate patterned with an array of electroconductive surface relief features on a surface of a substrate. In this approach, control over large-scale ordering is achieved via a planar pattern whose scale is on the order of tens of microns, a regime readily accessed through coarse lithography, laser micromachining, and holography.

Abstract: A photodetector has a spatially varying absorption spectrum formed in a monolithic InGaAsP structure whose quantum well active structure has modified effective bandgap properties. A waveguide couples light to the quantum well active structure. The spatially varying absorption spectrum allows wavelength-division demultiplexing. The effective bandgap properties can be modified by rapid thermal annealing to cause the diffusion of defects from one or two InP defect layers into the quantum well active structure.

Abstract: An optical sampler based on stable, non-absorbing optical hard limiters includes an optical feedback loop for storing an optical signal in optical form. The optical feedback loop includes appropriate components for amplifying/reproducing the stored optical signal. The optical sampler outputs the stored optical signal.

Abstract: Optical automatic gain control (AGC) is accomplished using stable, non-absorbing optical hard limiters and various optical logic gates derived therefrom. The AGC mechanism preserves the ratios between signal levels and provides an adjustable amount of gain.

Abstract: An optical switching device based on stable, non-absorbing optical hard limiters optically switches optical information from an input to a number of outputs based upon address information contained in the optical information. The optical switching device optically detects the location of the address bits in the optical information, optically samples the address bits, optically decodes the sampled address bits, optically activates an output based upon the decoded address bits, and optically outputs the optical information over the activated output.

Abstract: A laser has a spatially varying absorption spectrum formed in a monolithic InGaAsP structure whose quantum well active structure has modified effective bandgap properties. The spatially varying emission spectrum allows emission at multiple wavelengths or emission in a broad band. The effective bandgap properties can be modified by rapid thermal annealing to cause the diffusion of defects from one or two InP defect layers into the quantum well active structure. The laser can be implemented variously as a Fabry-Perot laser and a laser array.

Abstract: In a semiconductor laser, non-disordered quantum well active region functions as a lasing region. Surrounding the non-disordered quantum well active region is a disordered quantum well active region which prevents diffusion of injected carriers from the non-disordered quantum well active region or provides a lateral heterobarrier. The disordered quantum well active region is formed by rapid thermal annealing in which defects from one or two InP defect layers diffuse into the parts of the quantum well active region to be disordered.

Abstract: A quantum well optoelectronic device exploiting the multistability of the light-current characteristic of a multiple quantum well structure to achieve complex manipulation of the optical output of a light-emitting channel. Intraband tunneling of each of two distinct carrier types gives rise to a nonlinear dependence of optical gain on injected current.

Abstract: Analog noise is subtracted from an optical communication channel using stable, non-absorbing optical hard limiters. A reference signal B is combined with a control signal of intensity I2 through a 3 dB optical coupler to form a first combined signal having an intensity substantially equal to (B/2+I1). The first combined signal is processed by a first optical hard limiter to form a reflected signal having an intensity substantially equal to (I1−B/2). An information signal A is combined with a bias signal of intensity I2 through a 3 dB optical coupler to form a second combined signal. The reflected signal and the second combined signal are combined through a 3 dB optical coupler to form a third combined signal having an intensity substantially equal to 0.5(I1−B/2+A/2+I1). The third combined signal is processed by a second optical hard limiter to form a transmitted signal having an intensity substantially equal to 0.5(A−B). I2 is substantially equal to two times I1.