Incident Angle Dependence Research Articles

Laser induced threshold photoemission magnetic circular dichroism and its application to photoelectron microscope

This work enlightens the threshold photoemission magnetic circular dichroism (MCD) and its adaption on photoemission electron microscopy (PEEM) using lasers. MCD is a simple and efficient way to investigate magnetic properties since it does not need any spin analyzers with low efficiency, and thus the MCD related techniques have developed to observe magnetic domains. Usually, MCD in a total yield measurement in the valence band with weak spin–orbit coupling (SOC) excited by low photon energy (hν≤ 6eV) does not compete with the X-ray magnetic circular dichroism (XMCD) with strong SOC. XMCD PEEM observation of magnetic domains has been successfully established while MCD PEEM derived from valence bands has not been. However, using angle and energy resolved photoelectron, valence band MCD provides large asymmetry similar to that by XMCD. Threshold measurement of photoelectron in a total electron yield procedure can take advantage of the measurement of photoelectrons with a limited angle and energy mode. This restriction of the photoelectron makes the threshold MCD technique an efficient way to get magnetic information and gives more than 10% asymmetry for Ni/Cu(001), which is comparable to that obtained by angle resolved photoemission. Thus the threshold MCD technique is a suitable method to observe magnetic domains by PEEM. For threshold MCD, incident angle dependence and high sensitivity to out-of-plane magnetized films compared with in-plane ones are discussed. Ultrashort pulse lasers make it feasible to measure two photon photoemission MCD combined with PEEM, where resonant excitation has a possibility to enhance dichroic asymmetry. Recent results for valence band magnetic dichroism PEEM are presented.

Broadband and mid-infrared absorber based on dielectric-thin metal film multilayers

We propose a periodic multilayer structure of dielectric and metal interlayers to achieve a near-perfect broadband absorber of mid-infrared radiation. We examine the influence of four factors on its performance: (1) the interlayer metal conductance, (2) the number of dielectric layers, (3) a nanopatterned antireflective layer, and (4) a reflective metallic bottom layer for backreflection. Absorption characteristics greater than 99% of the 300 K and 500 K blackbody spectra are found for the optimized structures. Incident angle and polarization dependence of the absorption spectra are examined. We also investigate the possibility of fabricating a nanopatterned antireflective layer to maximize absorption.

Irradiation effects of water cluster ion beam on PMMA surface

We investigated the irradiation effects of a water cluster ion beam on a PMMA surface. The incident angle dependence of the sputter depth of the PMMA surface induced by the irradiation of a water cluster ion beam was measured. The sputter depth had a broad peak around the incident angle of 60°. The surface roughness caused by the irradiation of the water cluster ion beam was small compared with the sputter depth.

Incidence angle dependence of the enhancement factor in attenuated total reflection surface enhanced infrared absorption spectroscopy studied by numerical solution of the vectorial Maxwell equations

The finite element method (FEM) was used to solve the time-harmonic Maxwell equations in a study of the effect of the incidence angle of infrared light on the surface enhancement caused by colloidal gold particles in attenuated total reflection surface enhanced infrared absorption spectroscopy (ATR-SEIRAS). The spectral enhancement factor was obtained from computations of absorbance from a thin organic layer in the presence and absence of the metal nanostructure. For computations of an isolated particle the enhancement factor is high around the critical angle and decreases with an increase in incidence angle. This trend was also observed in experiments performed with gold particles immobilised on a silane modified silicon ATR crystal. Computations where gold particles are touching each other show low enhancement factors around the critical angle and an increase with increasing incidence angle. These two opposing trends are analysed based on the electric field distribution around the particle.

1P6-4 Characteristics of Incidence Angle Dependence of Plate Constructed with Phononic Crystal Structures(Poster Session)

1P6-4 Characteristics of Incidence Angle Dependence of Plate Constructed with Phononic Crystal Structures(Poster Session)

Control of Rabi Splitting Energies in CuCl Microcavities with HfO2/SiO2 Distributed Bragg Reflectors

Abstract The exciton-photon interaction in CuCl microcavities with HfO2/SiO2 distributed Bragg reflectors has been investigated from the viewpoint of the active-layer-thickness dependence of the interaction energy, the so-called vacuum Rabi splitting energy. The active layer thickness was changed from A/32 to A/5, where A corresponds to an effective resonant wavelength of the lowest-lying Z3 exciton. We performed angle-resolved reflectance measurements, and clearly detected three cavity-polariton modes originating from the lower, middle, and upper polariton branches in a strong coupling regime of the Z3 and Z1,2 excitons, and cavity photon. The incidence-angle dependence of the cavity-polariton energies was analyzed with a phenomenological Hamiltonian for the strong coupling. The vacuum Rabi splitting energies are systematically controlled from 22 (37) to 68 (122) meV for the Z3 (Z1,2) exciton with an increase in the active layer thickness. The active-layer-thickness dependence of the Rabi splitting energy is quantitatively explained using a simple model for quantum-well microcavities.

Measurements of SiO2, Polycrystalline Silicon, and Si3N4 Etching Yields Depending on Ion Incident Angle

The ion incident angle dependences of the etching yields of SiO2, polycrystalline silicon (poly-Si), and Si3N4 were studied using a plasma beam irradiation apparatus. The angle dependences were affected not only by the etchant chemistry produced by Ar and/or fluorocarbon gas plasmas, but also by the incident ion energy. Since the incident etchant characteristics were measured, the results are useful for constructing an etching profile simulator.

Incident angle dependence of absorption enhancement in plasmonic solar cells

The enhancement of solar light absorption in a solar cell is a challenging issue. In this article we show that in a thin-film silicon solar cell covered with silver nanoparticles on the surface, the absorption of the incident light can be particularly enhanced at certain angular range and wavelength. Such absorption enhancements are associated with the resonant localized surface plasmon (LSP) modes of the nanoparticle and nanoparticle-induced local Fabry-Perot (FP) modes. Our simulations suggest that the spectral shift of the LSP modes due to changing the incident angle leads to an incident-angle-sensitive absorption enhancement of the solar cell. Selecting the incident angle in a well-defined range of 0° to 35° is essential for optimizing the performance of a thin-film solar cell.

SU‐E‐T‐238: OnedosePlus MOSFET Dosimeter Performance in Tangential Field in Vivo Dosimtery

Purpose: To investigate the incident angle dependence of the OnedosePlus MOSFET dosimeter and to evaluate the dosimeterˈs performance in vivo dosimetry for tangential fields treatments. Methods: Two types of external beam radiation plan were generated based on a solid water phantom: one with a group of oblique beams directed toward the anterior surface of the phantom and other with two opposing half blocked beams directed parallel to the anterior surface. The second plan represented an extreme case of tangential field treatments. In the deliveries of the plans, OnedosePlus dosimeters were placed at various locations on the phantom anterior surface. Calibrated Radiochromic EBT2 film dosimeters were placed at the same locations of the phantom anterior surface and at the corresponding locations 1cm away from the anterior surface. The measured doses from the OnedosePlus dosimeters were compared against the corresponding doses in the plans and the film measurements. Results: As the incident beam angle increased from 0 to 90 degree to the CAX, the OnedosePlus reading increased 15%. The doses measured using the OnedosePlus dosimeters in the extreme tangential field plan did not have a clear correspondence to either the surface dose or the doses at 1 cm depth. The film readings were in close agreement with the TPS calculated doses with an average dose difference less than 5%. The OnedosePlus measured doses were higher than the TPS calculated doses at the 1cm depth by a constant (average: 31.45+/− 2.71cGy), and much higher than the surface film measurements by an average of 246%. Conclusions: OnedosePlus dosimeter readings have a strong dependence on the incident beam angle, especially when the beam angle is larger than 45 degree. The point of measurement for OnedosePlus dosimeter is unclear for the treatments involving tangential beams and it overestimates doses for the assumed point of measurement (1cm depth).

Negative Refraction and Energy-Transmission Efficiency of Acoustic Waves in Two-Dimensional Phononic Crystal: Numerical and Experimental Study

The negative refraction of acoustic waves in a two-dimensional phononic-crystal slab is studied by numerical simulation based on the finite-difference time-domain (FDTD) method and by ultrasonic measurement. The incident-angle dependences of energy-transmission efficiency in the simulation and experiment are in good agreement in the frequency range of approximately 1.2 MHz. Using the FDTD method, we optimize the efficiency by varying structural parameters such as filling fraction and slab thickness. The effect of deviation from the ideal crystallinity is also evaluated quantitatively via the simulation. These results indicate that an energetically efficient acoustic lens can be fabricated by carefully optimizing the structure of the phononic crystal.

Performance of see-through prism CPV module for window integrated photovoltaics

We have examined the performance of a see-through photovoltaics module that uses a low-concentration prism concentrator by undertaking ray-tracing analysis and an on-site experiment. The incident angle dependency of the prism concentrator makes it possible to concentrate direct solar radiation onto solar cells and transmit diffuse solar radiation. Fewer solar cells can then be used without sacrificing the conversion efficiency or lighting performance. The module generates approximately 1.15 more electricity than a conventional module while operating with 63% less solar cell area. We also introduce a design method for the concentrator geometry that adjusts the incident angle dependency for different latitude and tilt angles.

Control of exciton-photon interactions in CuCl microcavities

We have investigated the active-layer-thickness dependence of exciton-photon interactions in planar CuCl microcavities with HfO${}_{2}/$SiO${}_{2}$ distributed Bragg reflectors. The active layer thickness was changed from $\ensuremath{\lambda}/$32 to $\ensuremath{\lambda}/$4, while the cavity length was fixed at $\ensuremath{\lambda}/$2. We performed angle-resolved reflectance measurements and clearly detected three cavity-polariton modes, originating from the lower, middle, and upper polariton branches, in a strong-coupling regime of the ${Z}_{3}$ and ${Z}_{1,2}$ excitons and cavity photon. The incidence-angle dependence of the cavity-polariton modes was analyzed using a phenomenological Hamiltonian for the strong coupling. It was found that the interaction energies of the cavity-polariton modes, the so-called vacuum Rabi splitting energies, are systematically controlled from 22(37) to 71(124) meV for the ${Z}_{3}$(${Z}_{1,2}$) exciton by changing the active layer thickness from $\ensuremath{\lambda}/$32 to $\ensuremath{\lambda}/$4. The active-layer-thickness dependence of the Rabi splitting energy is quantitatively explained by a simple theory for quantum-well microcavities.

指向性を有する再帰反射材の試作及び日射反射特性の測定

Two kinds of directional retroreflective materials are manufactured, which are designed to show abrupt change in reflectance at the incident angle (Θ) of around 30 degrees. The measured solar reflectances are 17.7 percent for Θ ≥ 40 deg. and 39.0 percent for Θ ≤ 20 deg. for one type; 54.4 percent and 40.8 percent for the other. Building materials having these kinds of incident angle dependences can be used as cool roofs free of side effect; they can be high-reflective exclusively against summer sunlight, and low-reflective against other light sources, such as, winter sunlight, headlights of cars, and street lights.

Experimental demonstration of surface selection rules for SERS on flat metallic surfaces

We have measured the polarization and incident angle dependence of the Surface-Enhanced Raman Scattering (SERS) signal of a nile blue monolayer adsorbed on a flat gold surface. Comparisons with predictions of electromagnetic (EM) theory indicate that the molecules are predominantly adsorbed flat on the surface. These results provide the most direct demonstration of the concept of surface selection rules in SERS, and further confirm the validity of the SERS-EM model beyond the |E|(4)-approximation.

Velocity correlated multifragmentation inC60-surface impact: Energy distributions and incidence angle dependences

described within a scenario where Cn groups are statistically thermally emitted off an outgoing precursor away from the surface, as manifested by shifted Maxwellian flux distributions with only two parameters: kinetic energy per carbon atom associated with the center-of-mass velocity of the moving precursor and its temperature T. The best fitted parameters were found to be = 2.60 eV and kT= 0.86 eV. A distinct narrowing effect was observed for the incidence angle dependences of the C n fragments yield, going from C4 to C15 . The gradually decreasing angular width as a function of cluster size n was analyzed based on the assumption of isotropic, statistical fragments emission off an outgoing multifragmenting source the superhot precursor. The predicted 1 /n narrowing law was found to be in good agreement with the observed width effect and the two parameters , kT extracted from the independently measured kinetic-energy distributions. We conclude that both energy and angle distributions clearly demonstrate a statistical expansionlike, precursor-mediated multifragmentation mechanism.

First flight demonstration of film‐laminated InGaP/GaAs and CIGS thin‐film solar cells by JAXA's small satellite in LEO

AbstractJAXA is currently carrying out development of lightweight and flexible thin‐film solar cells for space application. The cells are thin‐film III–V multi‐junction solar cells with high efficiency and CuInGaSe2 solar cells with super radiation tolerance. The electrical performances of InGaP/GaAs dual‐junction solar cells and CIGS solar cells in space have been demonstrated by JAXA's small satellite, which flew in a Low‐Earth Orbit since January 2009. This flight demonstration is the first experiment for a thin‐film III–V multi‐junction solar cell in the world. Thin‐film solar cells were laminated using transparent polymer film in place of conventional coverglass for protection of solar cell's surface. The film‐laminated cells were observed for short‐circuit current degradation. The ground tests in which atomic oxygen, charged particles and ultraviolet rays were irradiated to the cells and films indicated that the cause of the degradation was attributed to the film coloring by obliquely incident UV rays. This is because the lamination film has UV‐reflective multilayer coating on its surface and the optical properties vary depending on the UV incident angle. The flight degradation trend of short‐circuit current was, therefore, predicted using the ground test results taking into account the incident angle dependence. The flight data and the predicted results were in reasonable agreement with each other. Thus, we could verify the validity of the ground tests and prediction methodology for film‐laminated solar cell in this study. Copyright © 2010 John Wiley & Sons, Ltd.

Design and fabrication of multi-layer antireflection coating for III-V solar cell

ZnS and ZnS–MgF 2 composite films were prepared on soda-lime glass substrates and MgF 2 films on GaAs by rf magnetron sputtering to investigate multi-layer antireflection (AR) coatings. Optical constants of these films were determined by envelope method and spectroscopic ellipsometry. In particular, ZnS–MgF 2 composite films were fabricated by co-sputtering of ZnS and MgF 2 target to obtain intermediate refractive index material for a middle layer in the triple-layer AR coating and these films exhibited the desired intermediate refractive index. Based on the extracted optical constants, single-, double- and triple-layer AR coatings on GaAs substrates were designed and fabricated by rf magnetron sputtering. Low reflectance could be obtained from single-layer AR coating only at a specific wavelength and could be obtained from multi-layer AR coating at wide wavelength regime. Additionally, incident angle dependence of the reflectance of the multi-layer AR coatings was also investigated and showed different behavior according to a number of layers.

Charge Transfer and Molecular Orientation of Tetrafluoro-tetracyanoquinodimethane on a Hydrogen-Terminated Si(111) Surface Prepared by a Wet Chemical Method

We investigated the chemical state and molecular orientation of 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4-TCNQ) adsorbed on a hydrogen-terminated Si(111) (1 × 1) surface using transmission infrared (IR) spectroscopy. We deposited F4-TCNQ molecules on H−Si(111) by a wet chemical method. Similar to evaporated F4-TCNQ molecules on various substrates in vacuum, we observed anionized F4-TCNQ on the H−Si(111) substrate. The incident angle dependence of the IR spectra reveals that this F4-TCNQ anion lies flatly on the surface. On the other hand, minority neutral F4-TCNQ species assume random orientation, judging from the comparison between s- and p-polarized IR spectra. We conclude that the first layer on the H−Si surface is a flat-lying anion species and the upper layers consist of randomly oriented neutral molecules.

3.6L: LateNews Paper: High Transmission and High Contrast PBS for Mobile Projection Applications

AbstractWe report the development and the successful product launch of a new 3M Polarizing Beam Splitter, 3M PBSA, which enables high performance optical engines for Liquid Crystal on Silicon LCOS projectors. This PBSA has typical effective transmission of 94% of polarized light with a double pass contrast of around 1500:1. Recent developments in contrast performance, incident angle dependency, and thermal stability are reported.

Incident angle dependency of propagating modes in rectangular grating for polarization‐independent −1ST order diffraction or polarization splitting

AbstractThe role of the incident angle of incoming light on the excited modes in rectangular grating at the interface of air and fused silica in Littrow mounting is investigated by the modal analysis.The analysis points out that the optimum effective refractive index difference for two propagating modes varies with the angle of incidence. In polarization‐independent −1st order diffraction, effective refractive index difference has the same value for the p‐ and s‐polarizations for incident angles from 30° to 37.5°, and a ratio of one‐third with the further increase of incident angle, to select the minimum aspect ratio of the grating dimensions. On the other hand, polarization splitting condition has a change of ratio of effective refractive index difference from a half to zero at an incident angle of 45.3°, where the coupling order of diffraction for p‐ or s‐polarization is also swapped. Such ratio of effective refractive index differences are seen as the ratio of modal periods in the variation of diffraction efficiency with the grating height. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1362–1369, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25163