Blocking of the polaron effect and spin-split cyclotron resonance in a two-dimensional electron gas

Cyclotron resonance (CR) of high density GaAs quantum wells exhibits well-resolved spin splitting above the LO-phonon frequency. The spin-up and spin-down CR frequencies are reversed relative to the order expected from simple band nonparabolicity. We demonstrate that this is a consequence of the blocking of the polaron interaction which is a sensitive function of the filling of the Landau levels.

Polarization-Independent Micro-Ring Resonator on Silicon-on-Insulator

Polarization-independent laterally-coupled micro-ring resonator has been designed and demonstrated. The origin of the polarization-sensitivity of the photonic wire waveguide (PWW) was analyzed. A polarization-insensitive PWW structure was designed and a polarization-insensitive MRR based on this PWW structure was designed by finite difference time-domain method and was fabricated on an 8-inch silicon-on-insulator wafer. The offset between the resonant wavelengths of the quasi-TE mode and the quasi-TM mode is smaller than 0.15 nm. The FSR is about 17 nm, extinction ratio about 10 dB and Q about 620.

Observation of photogalvanic current for interband absorption in InN films at room temperature

The linear and circular photogalvanic effects have been observed in undoped InN films for the interband transition by irradiation of 1060 nm laser at room temperature. The spin polarized photocurrent depends on the degree of polarization, and changes its sip when the radiation helicity changes from left-handed to right-handed. This result indicates the sizeable spin-orbit interaction in the InN epitaxial layer and provides an effective method to generate spin polarized photocurrent and to detect spin-splitting effect in semiconductors with promising applications on spintronics.

Mode analysis of photonic crystal polarization beam splitter and its application in integrated circuits design - art. no. 698437

In this work, the guided modes of a photonic crystal polarization beam splitter (PC-PBS) are studied. We demonstrate that the transmission of a low-loss photonic crystal 120 degrees waveguide bend integrated with the PBS will be influenced if the PBS is multi-moded. We propose a single-moded PC-PBS structure by introducing deformed structures, and it shows twice the enhancement of the transmission. This device with remarkable improvement of performance is promising in the use of photonic crystal integrated circuits design.

Compact polarization-insensitive arrayed waveguide grating based on SOI material

A compact polarization-insensitive 8x8 arrayed waveguide grating with 100GHz channel spacing at 1.55 mu m is presented on the material of silicon on insulator (SOI). Increasing the epitaxial layer thickness can reduce the birefringence of the waveguide, but the wvaeguide's bend radius also increases at the same time. We choose the SOI wafer with 3.0 mu m epitaxial layer to reduce the device's size and designed the appropriate structure of rib wave-guides to eliminate the polarization dependant wavelength shift. Compared to the other methods of eliminating the polarization dependant wavelength shift, the method is convenient and easy to control the polarization without additional etching process. The index differences between TE0 and TM0 of straight and bend waveguides are 1.4x10(-5) and 3.9x10(-5), respectively. The results showed that the polarization dependant wavelength shift is 0.1nm, and the device size is 1.5x1.0 cm(2).

Anomalous shift of the beating nodes in illumination-controlled In1-xGaxAs/In1-yAlyAs two-dimensional electron gases with strong spin-orbit interaction

The beating patterns in the Shubnikov-de Haas oscillatory magnetoresistance originating from zero-field spin splitting of two-dimensional electron gases (2DEGs) in In0.52Al0.48As/InxGa1-xAs/In0.52Al0.48As quantum wells with silicon delta doped on the upper barrier layer have been investigated by means of magnetotransport measurements before and after illumination. Contrary to the expectation, after each illumination, the beating nodes induced by the zero-field spin-splitting effect shift to lower and lower magnetic field due to the decrease in the zero-field spin-splitting energy of the 2DEGs. The anomalous phenomenon of the shift of the beating nodes and the decrease in spin-orbit coupling constants after illumination cannot be explained by utilizing the previous linear Rashba model. It is suggested that the decrease in the zero-field spin-splitting energy and the spin-orbit coupling constant arise from the nonlinear Rashba spin splitting.

Influence of band bending and polarization on the valence band offset measured by x-ray photoelectron spectroscopy

The influence of band bending and polarization on the valence band offset measured by x-ray photoelectron spectroscopy (XPS) is discussed, and a modification method based on a modified self-consistent calculation is proposed to eliminate the influence and thus increasing the precision of XPS. Considering the spontaneous polarization at the surfaces and interfaces and the different positions of Fermi levels at the surfaces, we compare the energy band structures of Al/Ga-polar AlN/GaN and N-polar GaN/AlN heterojunctions, and give corrections to the XPS-measured valence band offsets. Other AlN/GaN heterojunctions and the piezoelectric polarization are also introduced and discussed in this paper.

Polarization holographic high-density optical data storage in bacteriorhodopsin film

Optical films containing the genetic variant bacteriorhodopsin BR-D96N were experimentally studied in view of their properties as media for holographic storage. Different polarization recording schemes were tested and compared. The influence of the polarization states of the recording and readout waves on the retrieved diffractive image's intensity and its signal-to-noise ratio were analyzed. The experimental results showed that, compared with the other tested polarization relations during holographic recording, the discrimination between the polarization states of diffracted and scattered light is optimized with orthogonal circular polarization of the recording beams, and thus a high signal-to-noise ratio and a high diffraction efficiency are obtained. Using a He-Ne laser (633 nm, 3 mW) for recording and readout, a spatial light modulator as a data input element, and a 2D-CCD sensor for data capture in a Fourier-transform holographic setup, a storage density of 2 x 10(8) bits/cm(2) was obtained on a 60 x 42 mu m(2) area in the BR-D96N film. The readout of encoded binary data was possible with a zero-error rate at the tested storage density. (c) 2005 Optical Society of America.

Phonon-limited mobility in two-dimensional semiconductors with spin-orbit coupling

The authors demonstrate that the Rashba spin-orbit interaction in low-dimensional semiconductors can enhance or reduce the electron-phonon scattering rate by as much as 25%. The underlying mechanism is that the electron-phonon scattering phase space for the upper (lower) Rashba band is significantly enhanced (suppressed) by the spin-orbit interaction. While the scattering time decreases for the upper level, the mobility of the level increases due to an additional term in the electron velocity. (C) 2007 American Institute of Physics.

Radiation-matter oscillations in attosecond polarization beats using twin color-locked noisy lights

Based on the phase-conjugate polarization interference between two one-photon processes. When the laser has broadband linewidth, the sum-frequency polarization beat (SFPB) signal shows the autocorrelation of SFPB exhibits hybrid radiation-matter detuning terahertz damping oscillation. As an attosecond ultrafast modulation process, it can be extended intrinsically to any sum-frequency of energy-levels. It hits been also found that the asymmetric behaviors of the polarization beat signals result from the unbalanced dispersion effects, (c) 2005 Elsevier B.V. All rights reserved.

Polarization multiplexed write-once-read-many optical data storage in bacteriorhodopsin films

In polymeric films of bacteriorhodopsin (BR) a photoconversion product, which was named the F620 state, was observed on excitation of the film with 532 nm nanosecond laser pulses. This photoproduct shows a strong nonlinear absorption. Such BR films can be used for write-once-read-many (WORM) optical data storage. We demonstrate that a photoproduct similar or even identical to that obtained with nanosecond pulses is generated on excitation with 532 mn femtosecond pulses. This photoproduct also shows strong anisotropic absorption, which facilitates polarization storage of data. The product is thermally stable and is irretrievable to the initial B state either by photochemical reaction or through a thermal pathway. The experimental results indicate that the product is formed by a two-photon absorption process. Optical WORM storage is demonstrated by use of two polarization states, but more polarization states may be used. The combination of polarization data multiplexing and extremely short recording time in the femtosecond range enables very high data volumes to be stored within a very short time. (c) 2005 Optical Society of America.

Photochromic diarylethene for polarization holographic optical recording

Photochromic diarylethene, 1,2-bis[2-methyl-5-(3-fluorophenyl)-3-thienyl] perfluorocyleopentene (1a), was synthesized. The compound showed good photochromic reactions both in solution and in PMMA matrix by photo-irradiation. Using the diarylethene lb/PMMA film as recording medium and a He-Ne laser for recording and readout, four types of polarization holographic optical recording were accomplished for the first time. The results show that the orthogonal circular polarization recording is the best method for holographic optical recording when the target photochromic diarylethene is used as recording material. (c) 2006 Published by Elsevier B.V.

Theoretical design or single-polarization single-mode microstructured polymer optical fibres

Using the full-vector plane-wave expansion method, a kind of PMMA-based polarization-maintaining microstructured optical fibre (PM-mPOF) is theoretically studied. Dependence of the cutoff wavelengths of the two orthogonal polarization states (polarized along the two principal axes of PM-mPOF) on the structure parameters of the fibre is investigated in detail. A single-polarization single-mode (SPSM) PM-mPOF working in the visible region is designed and optimized with the result of the maximum SPSM bandwidth of 140 nm.

Polarization patterns control based on photoinduced anisotropy of photochromic fulgide

We investigate the photoinduced anisotropy of a photochromic material of pyrrylfulgide/PMMA films. It is proven that when the film is illuminated with a linear polarization light, an optical axis that has the same polarization as the excitation light could be induced in the film. A matrix of light spots with different polarizations is recorded on the pyrrylfulgide/PMMA film. When reading out with non-polarization light, the matrix of light spots shows no information of patterns. However, when reading out with different linear polarization lights, different patterns could be observed. The experiment confirms that the pyrrylfulgide/PMMA film could be used to record two different polarization patterns in a matrix of spots. This property may be applied in camouflage technology.