Exciton spectra, valence band splitting, and energy band structure of CuGaXIn1−XS2 and CuGaXIn1−XSe2 crystals

Exciton spectra are studied in CuGa_XIn_1−XS₂ solid solutions by means of photoreflectivity and wavelength modulation spectroscopy at liquid nitrogen temperature. The exciton parameters, dielectric constants, and free carrier effective masses are deduced from experimental spectra by calculations in the framework of a model taking into account the spatial dispersion and the presence of a dead-layer. The crystal field and spin orbit valence band splitting is calculated as a function of X taking into account the energy position of excitonic lines. The energy band structure of CuGa_XIn_1−XS₂ and CuGa_XIn_1−XSe₂ compounds is derived from optical spectra at photon energies higher than the fundamental band gap. The energies of optical transitions are tabulated for X values from 0 to 1.     

Optically induced mechanical interaction between semiconductor quantum dots under an electronic resonance condition

Assuming an electronic resonance condition, we study the shape-dependence of the radiation force (RF) on a semiconductor quantum dot (QD) floating in medium and the optically induced mechanical interaction (OIMI) between two QDs with Maxwell stress tensor (MST) method, where the response fields are calculated by the improved discrete dipole approximation (DDA). Main results are as follows: (1) Properties of the RF on an isolated QD drastically change due to its shape and polarization of an incident light, which can be used for shape-selective manipulation. (2) Anomalous OIMI between two QDs arises depending on the spatial structures of internal fields, which results from the interaction between polarizations in respective QDs when they are near each other.     

Time-domain Wave Propagation in Dispersive Media^①

The equation of time-domain wave propagation in dispersive media and the explicit beam propagation method are presented in this paper.This method is demonstrated by the short optical pulses in a directional coupler with second order dispersive effect and shows to be in full agreement with former references.This method is simple,easy and practical.     

Optical characterization of InGaAsN/GaAsN/GaAs quantum wells with InGaP cladding layers

Optical properties of InGaAsN/GaAs and InGaAsN/GaAsN/GaAs quantum well structures with InGaP cladding layers were studied by photoreflectance at various temperatures. The excitonic interband transitions of the InGaAsN/GaAsN/GaAs QW systems were observed in the spectral range above hν=E_g(InGaAsN). The confinement potential of the system with strain compensating GaAsN barriers became one step broader, thus more quantum states and larger optical transition rate were observed. A matrix transfer algorithm was used to calculate the subband energies numerically. Band gap energies, effective masses were adopted from the band anti-crossing model with band-offset values adjusted to obtain the subband energies to best fit the observed optical transition features. A spectral feature below and near the GaAs band gap energy from GaAs barriers is enhanced by the GaAs/InGaP interface space charge accumulation induced internal field.     

Thermally tuned optical fiber for true time delay generation

A new technique for generating a continuous range of true time delay values is introduced. Heating optical fiber in order to change the effective index of the guided mode produces time delays. A 45-m section of single-mode silica fiber is demonstrated to produce a continuous range of time delay values from 0 to 211 ps over a temperature tuning range of 50°C (30–80°C). A thermal time delay factor is introduced and found to be 0.096 ps/m°C for Corning LEAF fiber. A 7.66-m section of multimode Lucina polymer fiber is demonstrated to produce a range of time delay values from 0 to 32 ps over a temperature tuning range of 30°C (30–60°C). The thermal time delay factor for this fiber is −0.1427 ps/m°C.     

Physical layer performance benchmarking of two metropolitan area network configurations

This paper investigates the problem of dynamic survivable lightpath provisioning against single-node/link failures in optical mesh networks employing wavelength-division multiplexing (WDM).We unify various forms of segment protection into generalized segment protection (GSP). In GSP, the working path of a lightpath is divided into multiple overlapping working segments, each of which is protected by a node-/link-disjoint backup segment. We design an efficient heuristic which, upon the arrival of a lightpath request, dynamically divides a judiciously selected working path into multiple overlapping working segments and computes a backup segment for each working segment while accommodating backup sharing. Compared to the widely considered shared-path protection scheme, GSP achieves much lower blocking probability and shorter protection-switching time for a small sacrifice in control and management overhead.On the basis of generalized segment protection, we present a new approach to provisioning lightpath requests according to their differentiated quality-of-protection (QoP) requirements. We focus on one of the most important QoP parameters—namely, protection-switching time—since lightpath requests may have differentiated protection-switching-time requirements. For example, lightpaths carrying voice traffic may require 50 ms protection-switching time while lightpaths carrying data traffic may have a wide range of protection-switching-time requirements. Numerical results show that our approach achieves significant performance gain which leads to a remarkable reduction in blocking probability.While our focus is on the optical WDM network, the basic ideas of our approaches can be applied to multi-protocol label switching (MPLS) networks with appropriate adjustments, e.g., differentiated bandwidth granularities.     

All-optical logic AND-NOR gate with three inputs based on cross-gain modulation in a semiconductor optical amplifier

We report the realization of a novel all-optical logic AND-NOR gate based on cross-gain modulation (XGM). The used scheme requires only one SOA to perform the logic gate with three input signals. A 8.5 dB dynamic extinction ratio with a switching time of about 650 ps for the rise time and 100 ps for the fall time.     

Dependence of film thickness on the electrical and optical properties of ZnO-Cu-ZnO multilayers

ZnO-Cu-ZnO multilayers were prepared by simultaneous RF magnetron sputtering of ZnO and DC magnetron sputtering of Cu. Cu films with different thickness were used as the intermediate metal layer. The optical and electrical properties of the multilayers studied by UV-vis spectrophotometer and four point probe method, respectively, shows that transmittance increases with decrease of copper thickness up to an optimum thickness of 5 nm and sheet resistance decreases with increase of thickness. Low resistivity and high transmission were obtained when the film structure has a thickness of ZnO/Cu/ZnO: 50/5/50 nm. The performance of the multilayers as transparent conducting material was better than the single layer ZnO of equal thickness.     

Measuring small wavelength differences by heterodyne interferometry and optical activity of chiral crystal

The optical activity of a chiral crystal and common-path heterodyne interferometry are used in a simple measurement technique that was developed to measure small wavelength differences. When circularly polarized heterodyne light passes through a chiral crystal, the plane of polarization rotates. The phase difference between the right- and left-circular lights is directly proportional to the angle of rotation. The rotation angle depends strongly on the wavelength. The phase difference can be accurately detected and substituted into specially derived equations to estimate wavelength variations. The feasibility of this method was demonstrated and the wavelength sensitivity was about 0.00812 nm. This method provides the advantages of a simple structure, ease of operations, a large wavelength measurement range and high sensitivity.     

Simulation of vertical merged MOS elements with optical power supply

Functional optoelectronic vertical merged MOS (OVMMOS) elements with optical power supply increasing the packaging density for advanced high-speed low-voltage low-power deep-submicron ULSI are considered. Two types of new OVVMOS logical elements are proposed, analyzed and simulated. The simple reduced but adequate numerical electrical-optical model for the OVMMOS is formulated. Low-voltage low-power OVMMOS with combined channels for electrons and holes to increase integration level are simulated using two-dimensional (2D)-numerical device simulators. The problems of low light power operations and optimizations of OVMMOS elements are investigated using 2D simulators.