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Spin photocurrent spectra induced by Rashba- and Dresselhaus-type circular photogalvanic effect (CPGE) at inter-band excitation have been experimentally investigated in InGaAs/AlGaAs quantum wells at a temperature range of 80 to 290 K. It is found that, the sign of Rashba-type current reverses at low temperatures, while that of Dresselhaus-type remains unchanged. The temperature dependence of ratio of Rashba and Dresselhaus spin-orbit coupling parameters, increasing from -6.7 to 17.9, is obtained, and the possible reasons are discussed. We also develop a model to extract the Rashba-type effective electric field at different temperatures. It is demonstrated that excitonic effect will significantly influence the Rashba-type CPGE, while it has little effect on Dresselhaus-type CPGE.

Multiple-state storage (MSS) is common for resistive random access memory, but the effects of plasma treatment on the MSS and the switching properties have been scarcely investigated. We have demonstrated a stable four-state storage capability of single zinc oxide nanowire (ZnO NW) treated by argon plasma. The electrical switching is attributed to the electron trapping and detrapping from the oxygen vacancies (Vos). The MSS relates to the electrical-thermal induced distribution of the Vos which determines electron transport behavior to show different resistance states. Additionally, programming (set and reset) voltages decrease with plasma treatment due to the thickness modulation of the interface barrier.

The in-plane optical anisotropy (IPOA) in (001)-grown GaAs/AlGaAs quantum wells (QWs) with different well widths varying from 2 nm to 8 nm has been studied by reflectance difference spectroscopy. Ultra-thin InAs layers with thickness ranging from 0.5 monolayer (ML) to 1.5 ML have been inserted at GaAs/AlGaAs interfaces to tune the asymmetry in the QWs. It is demonstrated that the IPOA can be accurately tailored by the thickness of the inserted ultra-thin InAs layer at the interfaces. Strain-induced IPOA has also been extracted by using a stress apparatus. We find that the intensity of the strain-induced IPOA decreases with the thickness of the inserted InAs layer, while that of the interface-induced IPOA increases with the thickness of the InAs layer. Theoretical calculations based on 6 band k ⋅ p theory have been carried out, and good agreements with experimental results are obtained. Our results demonstrate that, the IPOA of the QWs can be greatly and effectively tuned by inserting an ultra-thin InAs layer with different thicknesses at the interfaces of QWs, which does not significantly influence the transition energies and the transition probability of QWs.

Tin sulphide films with thickness of 500~1000 nm were deposited on ITO glass substrates at 30~150°C by a thermal evaporation technique. The films were characterized with X-ray diffraction (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM) analysis. The vibrational property of the films was examined by Raman spectra. The SnS films are polycrystalline with a strong {111} preferred orientation, and they have orthorhombic crystal structure with a grain size of a few ten nanometers and exhibited near stoichiometric SnS composition. Their lattice parameters are a=0.4309~0.4313 nm, b=1.1263~1.1273 nm, c=0.3981~0.3990 nm which closely resembles those of bulk SnS at room temperature. And the substrate temperature has some influence on the composition and structure of the deposited films: when the substrate temperature increases from 30°C to 150°C, the grains in the films become smaller and the crystallinity has been improved. sulphide films with thickness of 500~1000 nm were deposited on ITO glass substrates at 30~150°C by a thermal evaporation technique. The films were characterized with X-ray diffraction (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM) analysis. The vibrational property of the films was examined by Raman spectra. The SnS films are polycrystalline with a strong {111} preferred orientation, and they have orthorhombic crystal structure with a grain size of a few ten nanometers and exhibited near stoichiometric SnS composition. Their lattice parameters are a=0.4309~0.4313 nm, b=1.1263~1.1273 nm, c=0.39810~.3990 nm which closely resembles those of bulk SnS at room temperature. And the substrate temperature has some influence on the composition and structure of the deposited films: when the substrate temperature increases from 30°C to 150°C, the grains in the films become smaller and the crystallinity has been improved.

Thermal emission spectral data sets were collected for a thin solid film (parafilm) and a thin liquid film (isopropanol) on the interval of 298–348 K. The measurements were performed using a conventional Fourier transform infrared (FT-IR) spectrometer with external optical bench and in-house-designed emission cell. Both DTGS and MCT detectors were used. The data sets were analyzed with band-target entropy minimization (BTEM), which is a pure component spectral reconstruction program. Pure component emissivities of the parafilm, isopropanol, and thermal background were all recovered without any a priori information. Furthermore, the emissivities were obtained with increased signal-to-noise ratios, and the signals due to absorbance of thermal radiation by gas-phase moisture and CO2 were significantly reduced. As expected, the MCT results displayed better signal-to-noise ratios than the DTGS results, but the latter results were still rather impressive given the low temperatures used in this study. Comparison is made with spectral reconstruction using the orthogonal projection approach–alternating least squares (OPA-ALS) technique. This contribution introduces the primary equation for emission spectral reconstruction using BTEM and discusses some of the unusual characteristics of thermal emission and their impact on the analysis.

In this study, tin precursor layers were deposited on ITO glass substrates by thermal evaporation, and sulphurised in a vacuum furnace at the temperature range between 423-673K, in order to translate the tin layers into compound SnS layers. All the layers synthesized were characterized with X-ray diffractograms, microstructure analysis. It was found that the best SnS films were synthesized for sulphurisation at temperature 573-673K, and they were polycrystalline with a strong {111} preferred orientation, and they had orthorhombic crystal structure with a grain size of a few hundred nanometers and exhibited near stoichiometric SnS composition. The near stoichiometric SnS film was measured to have a p-type electrical conductivity and a resistivity of the order of 10 2 Ω.cm , and its optical properties were investigated using spectrophotometric measurements of the transmittance and reflectance at normal incidence in the wavelength range 400-2500nm, the films were transparent for a wavelength >1250nm.

A modified direct method for subtracting axial scattered light was put forward, that is, when the collimated transmission measured, the axial scattered light was deducted by a small angle scattered light with the same beam size. And μ t values of two different samples of human whole blood were measured at laser wavelengths of 488,632.8 and 1341.4nm, respectively. It showed that μ t was different for the same blood sample at different wavelength and for different blood sample at the same wavelength.

Monte Carlo method is used to simulate light distribution in human artery of three layers that is irradiated respectively by two different surface photon sources (Guassian beam and flat beam) of 0.06cm radii at wavelength of 633nm. Fluence, diffuse reflectance and diffuse transmission distribution of the tissue are given when the two surface photon sources illuminate the tissue respectively. The influence of the shape of the incident beam on the above parameters, and that of the refractive index n on the diffuse reflectance Rd and absorptance A of the tissue, are discussed. The obtained results are: the diffuse reflectance Rd and fluence Φ are mainly distributed in radial scale of the size of the incident beam, and the influence of the shape of the incidence beam on the radial distribution of Rd and Φ is also in the scale of the size of the incident beam, whereas that of the shape of the incident light beam on the diffuse transmission is little. Rd is linearly decreased with the increasing of n in each layer tissue, but the influence of n in deeper layer tissue on Rd is little; absorptance is linearly increased with the increasing of n in each layer tissue. Therefore, the refractive index is a very important parameter in biotissue.

The relationships between the diffuse reflectance of tissue and its optical parameters (especially the refractive index and the ratio N' of effective scattering coefficient to absorption coefficient) are studied by Monte Carlo method. The limitation in the diffuse reflectance formula fitted by others is found, and a new diffuse reflectance formula which is different for N' in different region is presented. And the diffuse reflectance formulas are obtained for N' = 2 ~ 20 and N' = 40 ~ 100, respectively.© (2004) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Novel charge-mosaic composite membranes composed of cation and anion permeable domains were prepared. Poly(4-methylstyrene-isoprene-styrene-isoprene-4-methylstyrene) pentablock copolymer (MsISIMs), poly(isoprene-4-methylstyrene) diblock copolymer (IMs), and poly(isoprene-styrene-isoprene) triblock copolymer (ISI), used as the precursor of the charge-mosaic membranes, were polymerized from styrene (S), isoprene (I), and 4-methylstyrene (Ms). MsISIMs and a blend of ISI and IMs were then dissolved in benzene and cast on a polypropylene microporous supporting membrane. After chemical modification, the MsISIMs and IMs/ISI charge-mosaic composite membranes were obtained. Our experimental results show that the IMs/ISI charge-mosaic composite membrane is similar in membrane structure and properties to the MsISIMs charge-mosaic composite membrane.

Based on the principle of total internal reflection, a new experimental system , in which the sample is close sandwiched between two prisms, was designed to determine the refractive indices of biotissues and homogeneous medium. Some mammalian tissues have been determined at laser wavelengths ofO.488, 0.6328, 1.0795 and 1.3414?tm, respectively, and their dispersion equations have been obtained. And the absolute error between the n calculated from the dispersion equation and the measured is within 0.002. By utilizing these dispersion equations, the refractive indices of the tissues can be obtained at any wavelength within the waveband of O.488-1.3414?m. The method has great reliability and accuracy, and it can be used for measuring the refractive indices of biotissues and any other medium.

The mode splitting induced by electro-optic birefringence in a P—I—N InGaAs/GaAs/AlGaAs vertical-cavity surface-emitting laser (VCSEL) has been studied by polarized electroluminescence (EL) at room temperature. The polarized EL spectra with E || [110] and E || [10] directions, are extracted for different injected currents. The mode splitting of the two orthogonal polarized modes for a VCSEL device is determined, and its value increases linearly with the increasing injected current due to electro-optic birefringence. This article demonstrates that the polarized EL is a powerful tool to study the mode splitting and polarization anisotropy of a VCSEL device.

Polarized Raman scattering measurement on single wurtzite c-plane (001) ZnO nanorod grown by hydrothermal method has been performed at room temperature. The polarization dependence of the intensity of the Raman scattering for the phonon modes A1(TO), E1(TO), and E2high in the ZnO nanorod are obtained. The deviations of polarization-dependent Raman spectroscopy from the prediction of Raman selection rules are observed, which can be attributed to the structure defects in the ZnO nanorod as confirmed by the comparison of the transmission electron microscopy, photoluminescence spectra as well as the polarization dependent Raman signal of the annealed and unannealed ZnO nanorod. The Raman tensor elements of A1(TO) and E1(TO) phonon modes normalized to that of the E2high phonon mode are |a/d|=0.32±0.01, |b/d|=0.49±0.02, and |c/d|=0.23±0.01 for the unannealed ZnO nanorod, and |a/d|=0.33±0.01, |b/d|=0.45±0.01, and |c/d|=0.20±0.01 for the annealed ZnO nanorod, which shows strong anisotropy compared to that of bulk...

We theoretically study the influence of the spin—orbit coupling (SOC) on the in-plane optical anisotropy (IPOA) induced by in-plane uniaxial strain and interface asymmetry in (001) GaAs/AlGaAs quantum wells (QWs) with different well width. It is found that the SOC has more significant impact on the IPOA for the transition of the first valence subband of heavy hole to the first conduction band (1H1E) than that of 1L1E. The reason has been discussed. The IPOA of (001) InGaAs/InP QWs has been measured by reflectance difference spectroscopy, whose amplitude is about one order larger than that of GaAs/AlGaAs QWs. The anisotropic interface potential parameters of InGaAs/InP QWs are also determined. The influence of the SOC effect on the IPOA of InGaAs/InP QWs when the QWs are under tensile, compressive or zero biaxial strain are also investigated in theory. Our results demonstrate that the SOC has significant effect on the IPOA especially for semiconductor QWs with small well width, and therefore cannot be ignored.

The mode splitting induced by electro-optic birefringence in an P-I-N InGaAs/GaAs/AlGaAs vertical-cavity surface-emitting laser (VCSEL) has been studied by photocurrent difference spectroscopy (PCDS) at room temperature. The mode splitting, anisotropic broadening width, and the anisotropic integrated area of the two orthogonal polarized modes for a VCSEL device are determined. The mode splitting changes linearly with the injected current, which agree very well with theoretical calculations using a Jones matrix approach. It is demonstrated that the PCDS is a powerful tool to study the cavity anisotropy of a VCSEL device.

Tin sulphide (SnS) films with thicknesses of 65–580 nm have been deposited on glass substrates by thermal evaporation. The physical properties of the films were investigated using X-ray diffraction, scanning electron microscopy, atomic force microscopy, Raman spectroscopy and ultraviolet–visible–near-infrared spectroscopy measurements at room temperature. It is indicated that the deposited films mainly exhibit SnS phase, but they contain tiny SnO2. The deposited SnS films are pinhole free, smooth and strongly adherent to the surface of the substrate. With the increase of the film thickness from 65 to 580 nm, the colour of the SnS films changes from brown to dark brown to grey, and the grains and roughness of the films become larger and larger, but the direct bandgap decreases. All the films have larger direct bandgap of 1.55–2.28 eV, which is much larger than the 1.3 eV of bulk SnS.

Sn-based nanocrystals were prepared by depositing Sn-rich SiO2 films using a cosputtering process and a subsequent vacuum annealing. Transmission electron microscopy (TEM) and x-ray diffraction showed formation of Sn nanocrystals evenly distributed in SiO2 matrix at relatively low annealing temperature of 400°C. The size of Sn nanocrystals increased with increasing annealing temperature. X-ray photoelectron spectroscopy revealed that Sn was partially oxidized during the cosputtering process forming Sn oxide nanoclusters of 3.4±0.6nm in diameter after annealing, as observed by TEM. The Sn-based nanocrystal films exhibited wide optical bandgap around 4.2–4.4eV and a slightly high-energy shift with increasing annealing temperature. This result is in close agreement with the absorption in the Sn oxide nanoclusters as well as Sn-related oxygen defects in the matrix.