Total Reflection Condition Research Articles

Polar magneto-optical effects in magnetoplasmonic thin films illuminated by attenuated total reflection

We investigate the polar magneto-optical Kerr effect as a function of the angle of incidence in Co/Au thin films under attenuated total reflection conditions. An experimental method is proposed to measure the intrinsic polar magneto-optical Kerr rotation of the magnetoplasmonic films while considering the influence of the glass Faraday magneto-optical effect. The experimental results demonstrate that the Kerr rotations of these films are greatly affected by a number of factors including the angle of incidence, the linear polarization of the incident light, and the film thickness. The results suggest that the polar magneto-optical activity is affected by the evanescent fields decaying inside the films; these fields arise not only from attenuated total reflection at the glass/metal interface but also from the surface plasmon polaritons at the metal/air interface. A close relationship between the magneto-optical activity and the electromagnetic field distribution within the magnetoplasmonic films is clearly revealed.

Wave propagation of induced radiation in microcapillary holes of a glass microchannel plate

Soft x-ray reflection and transmission spectra of radiation propagating inside microchannel plates have been analyzed in the framework of the wave approximation. X-ray and fluorescence yields due to the grazing incidence reflection phenomenon have been investigated with respect to the geometry of the channel walls. We also discuss x-ray absorption near-edge structure spectra collected at the exit of microcapillaries under the total x-ray reflection condition, taking into account a surface transition layer at the sample surface. The fine structures and the angular distribution of the transmitted radiation have been interpreted in the energy range of the anomalous dispersion of the Si L2,3 edges.

Control of magnetic contrast with nonlinear magneto-plasmonics.

The interaction between surface plasmons (SP) and magnetic behavior has generated great research interest due to its potential for future magneto-optical devices with ultra-high sensitivity and ultra-fast switching. Here we combine two surface sensitive effects: magnetic second-harmonic generation (MSHG) and SP to enhance the detection sensitivity of the surface magnetization in a single-crystal iron film. We show that the MSHG signal can be significantly enhanced by SP in an attenuated total reflection (ATR) condition, and that the magnetic contrast can be varied over a wide range by the angle-of-incidence. Furthermore, the magnetic contrast of transverse and longitudinal MSHG display opposite trends, which originates from the change of relative phase between MSHG components. This new effect enhances the sensing of magnetic switching, which has potential usage in quaternary magnetic storage systems and bio-chemical sensors due to its very high surface sensitivity and simple structure.

Opto-mechanical probe for combining atomic force microscopy and optical near-field surface analysis.

We have developed a new easy-to-use probe that can be used to combine atomic force microscopy (AFM) and scanning near-field optical microscopy (SNOM). We show that, using this device, the evanescent field, obtained by total internal reflection conditions in a prism, can be visualized by approaching the surface with the scanning tip. Furthermore, we were able to obtain simultaneous AFM and SNOM images of a standard test grating in air and in liquid. The lateral resolution in AFM and SNOM mode was estimated to be 45 and 160 nm, respectively. This new probe overcomes a number of limitations that commercial probes have, while yielding the same resolution.

Spectroelectrochemical and DFT Study of Thiourea Adsorption on Gold Electrodes in Acid Media

The adsorption of thiourea (TU) at Au(111) and Au(100) single crystal and evaporated gold thin-film electrodes with preferential (111) orientation was studied in perchloric acid solutions with TU concentrations below 0.1 mM. For this purpose, cyclic voltammetry with gold single crystals was combined with external reflection infrared spectroscopy and surface-enhanced infrared reflection-absorption spectroscopy under attenuated total reflection conditions (ATR-SEIRAS) with gold thin film electrodes. In situ surface enhanced Raman spectroscopy (SERS) experiments were also carried out with these latter samples. In addition, optimized geometries and theoretical harmonic vibrational frequencies, obtained from B3LYP/LANL2DZ, 6-31+G(d) calculations for TU and thioureate species adsorbed on Au clusters with (111) orientation, were used for the interpretation of the experimental spectra. ATR-SEIRAS experiments show irreversible adsorption of TU at 0.10 V, whereas the SERS experiments have confirmed the bonding of the TU molecule to the metal surface through the S atom. The optimized geometry obtained from density functional theory (DFT) calculations for adsorbed TU corresponds to unidentate bonding through the sulfur atom, with the Au-S bond slightly tilted (13°) from the surface normal, whereas the C-S bond appears to be tilted by 45°. In the case of adsorbed thioureate, under the application of an external electric field of 0.01 a.u., a bidentate asymmetrical bridge adsorption configuration is obtained with one N(H) and the S atoms bonded to Au in positions close to top adsorption sites and with the molecular plane perpendicular to the metal surface. The observation of an adsorbate band for the asymmetric NCN stretching in the experimental infrared spectra confirms the tilting of the S-C bond of the adsorbed TU at low potentials. Changes of the adsorbate bands in the ATR-SEIRA spectra at potentials around 0.60 vs reversible hydrogen electrode (RHE) can be interpreted on the basis of DFT results as due to the deprotonation of adsorbed TU to form adsorbed thioureate. © 2014 American Chemical Society.

TRHEPD rocking curve analyses of Pt/Ge(001) and TiO2(110) surfaces

Recently, we developed new total reflection high-energy positron diffraction (TRHEPD) apparatus [1] on a beam line of the linac-based intense positron beam of the Slow Positron Facility at KEK, Japan. The high intensity allows us to install a brightness-enhancement section, which to observation of clear positron diffraction patterns for crystal surfaces under total reflection condition. In this work, we investigated the atomic configuration of Pt-induced nanowires formed on a Ge(001) surface [2] using the apparatus. By means of the diffraction intensity analysis based on the dynamical diffraction theory, or TRHEPD rocking curve analysis, a previously proposed theoretical model [D. E. P. Vanpoucke et al., Phys. Rev. B 77, 241308(R) (2008)], composed of Ge dimers on the top layer and buried Pt arrays in the second and fourth layers, was confirmed to be the fundamental structure of the nanowire. We also investigated the atomic configuration of a rutile-TiO2(110) surface. It is well known that the structure of this surface transforms its periodicity from (1×1) to (1×2) by elevating the sample temperature above ~1100 K, whereas the detailed structure is yet to be revealed. There is a longstanding controversy between the structure models proposed by scanning tunneling microscopy, low energy electron diffraction, surface X-ray diffraction, first-principles calculation with density functional theory results, etc. To solve the problem, we have measured TRHEPD rocking curves and determined the atomic arrangements of the topmost crystal surface [3].

Total reflection high-energy positron diffraction (TRHEPD)

Total reflection high-energy positron diffraction (TRHEPD) promises to be an ideal technique for determining the atomic arrangement of solid surfaces. TRHEPD makes full use of the total reflection of the positron beam from a surface in reflection high-energy positron diffraction (RHEPD), the positron counterpart of reflection high-energy electron diffraction (RHEED). Owing to the development and use of a brightness-enhanced intense positron beam at KEK, it is now possible to obtain clear TRHEPD patterns. It is shown that the TRHEPD pattern from a Si(111)-7×7 reconstructed surface for the total reflection condition does not contain contributions from atoms in the bulk.

Total reflection high-energy positron diffraction: An ideal diffraction technique for surface structure analysis

It is shown that the reflection high-energy positron diffraction (RHEPD) pattern from a Si(111)-(7 × 7) reconstructed surface for the total reflection condition, that is, the total reflection high-energy positron diffraction (TRHEPD) pattern, does not contain contributions from atoms in the bulk. Now, a method of observing the diffraction pattern formed only by the atoms on the topmost surface by a straightforward measurement of a bulk sample is available.

Transmission of Electromagnetic Waves Through Plane-Parallel Layers Under Total Reflection Conditions

Analytical expressions are obtained for and used in calculations of the transmittance of thin (on the order of a wavelength) layers under conditions of total reflection at one of the boundaries in the general case of linearly polarized radiation where the oscillation azimuth of the incident wave is not 0 or π/2. The transmittances of this kind of layer for TE (s-polarization) and TM (p-polarization) waves are compared. The analytic expressions are used to calculate the dependence of the energy transmittance on layer thickness for a fixed angle of incidence and different oscillation azimuths of a linearly polarized incident wave, as well as for several angles of incidence (including the critical angle) with a fixed oscillation azimuth.

Single-mode dynamic X-ray diffraction for Si and Si nanowires on Si

A method is reported of realizing single-mode diffraction using singly polarized X-ray wide-angle incidence and grazing-emergence diffraction from a bare Si substrate and from Si nanowires on an Si substrate. For a bare Si substrate, the surface-diffracted and specularly reflected beams of single-mode excitation are separated owing to the extremely asymmetric diffraction at grazing emergence. For Si wires on Si, single-mode diffraction is achieved by tuning the X-ray energy or the azimuthal angle under the conditions of total reflection. This finding opens up new opportunities for using crystal diffraction, in addition to optical reflection or refraction, for the design of coherent X-ray optics.

<i>In Situ</i> Microscope Measurements of the Formation of Nanometer-Sized Gold Particles at the Dodecane/Water Interface through the Direct Reduction of Aqueous Tetrachloroaurate(III) by Hydrophobic <i>dl</i>-α-Tocopherol in the Presence of 1,10-Phenanthroline

The contact of a dodecane solution of hydrophobic dl-α-tocopherol with an aqueous solution of tetrachloroaurate(III) resulted in the direct reduction of tetrachloroaurate(III) and the formation of gold particles at the dodecane/water interface. Without other additives, the gold particles were unfavorably aggregated with each other and chains of gold particles were formed. In the present study, a chemical preventing the aggregation was sought. Fourteen types of chemicals were individually added to the two-phase system, and then the size, shape, and movements of the gold particles formed at the dodecane/water interface were observed through an optical microscope using bright-field illumination, using dark-field illumination, or with scattered laser light under total internal reflection conditions. Of the 14 chemicals, 1,10-phenanthroline (phen) effectively prevented the aggregation of gold particles at the interface. The gold particles formed in the presence of phen under the optimized conditions were recovered on a coverslip, and their size and shape were recorded using an atomic force microscope. Almost all of the recovered gold particles were not higher than 50 nm and this meant that nanometer-sized gold particles were formed.

Huygens’ Principle: Exact wavefronts produced by aspheric lenses

We obtain simple exact formulas for the refracted wavefronts through plano-convex aspheric lenses with arbitrary aspheric terms by considering an incident plane wavefront propagating along the optical axis. We provide formulas for the zero-distance phase front using the Huygens' Principle and the Malus-Dupin theorem. Using the fact that they are equivalent, we have in the second method found a way to use an improper integral, instead of the usual evaluated integral, to arrive at these formulas. As expected, when the condition of total internal reflection is satisfied, there is no contribution to the formation of the refracted wavefront.

Principles of X-ray diffractometry of surface acoustic waves

Theoretical fundamentals of modern methods of X-ray diffractometry of surface acoustic waves (SAW) are considered briefly. X-ray diffraction on SAW-modulated crystals under total external reflection conditions and the Bragg conditions for the YZ-cut of the LiNbO3 crystal is considered. Agreement of theoretical and experimental results makes it possible to use them for SAW diagnostics. Possibilities and limitations of listed methods for determining the SAW field parameters are discussed.

Observation of hybrid state of Tamm and surface plasmon-polaritons in one-dimensional photonic crystals

Experimental observation of hybrid mode of Tamm plasmon-polariton and surface plasmon-polariton is reported. The hybrid state is excited in one-dimensional photonic crystal terminated by semitransparent metal film under conditions of total internal reflection for transverse-magnetic-polarized light. Coupling between Tamm and surface plasmon-polaritons leads to repulsion of their dispersion curves controlled by metal film thickness.

Three-dimensional modeling of light rays on the surface of a slanted lenticular array for autostereoscopic displays

In this paper, we developed an optical model describing the behavior of light at the surface of a slanted lenticular array for autostereoscopic displays in three dimensions and simulated the optical characteristics of autostereoscopic displays using the Monte Carlo method under actual design conditions. The behavior of light is analyzed by light rays for selected inclination and azimuthal angles; numerical aberrations and conditions of total internal reflection for the lenticular array were found. The intensity and the three-dimensional crosstalk distributions calculated from our model coincide very well with those from conventional design software, and our model shows highly enhanced calculation speed that is 67 times faster than that of the conventional software. From the results, we think that the optical model is very useful for predicting the optical characteristics of autostereoscopic displays with enhanced calculation speed.

X-ray micro-tomography using white beam radiation from SPring-8

An X-ray micro-tomography system using white beam radiation was developed. A flat mirror was used to eliminate X-rays with energies higher than the critical energy of the mirror under the total reflection condition. To enlarge the field of view in the reflected beam, a simple mechanical bender was used to expand the beam in the vertical direction. A single tomographic dataset was obtained with the scanning time of 0.5sec using a fast rotational sample stage. The dominant X-ray energy which contributed to the image formation in the tomographic measurement was estimated from the linear absorption coefficient of the standard samples.

Optical Simulation Study on the Effect of Diffusing Substrate and Pillow Lenses on the Outcoupling Efficiency of Organic Light Emitting Diodes

The effect of diffusing substrate and pillow lenses on the outcoupling efficiency of organic light-emitting diodes (OLEDs) was studied by optical simulation based on the point-dipole model. The diffusing substrate included Mie scatterers by which the condition of total internal reflection could be broken. The finite-difference time-domain method was used to obtain the intensity distribution on the transparent electrode of an OLED, which was used as a light source to carry out a ray-tracing simulation of the OLED and the diffusing substrate. It was found that the outcoupling efficiency of the OLED was sensitive to the thickness of organic layers and could be increased by 21.0% by adopting a diffusing substrate in which Mie scatterers whose radius was 2.0 μm were included at the density of 10 7 mm -3 and by 65.5% by forming one pillow lens with the radius of 2 mm on the front surface of the glass substrate. This study revealed that the outcoupling efficiency could be improved by adopting diffusing substrate and pillow lenses along with the optimization of the thickness of each layer in the OLED.

Transparent and flexible multi-layer films with graphene recording layers for optical data storage

Based on the polarization-sensitive absorption of graphene under conditions of total internal reflection, we demonstrate the fabrication and reading of transparent and flexible multi-layer-film optical data storage media based on graphene recording layers. We report a realization of the process of data writing-transferring-reading by repeatedly transferring recorded graphene and its strong polarization effect. The reading results show a high signal-to-noise ratio and stability and low crosstalk interference between the layers. In addition, the graphene-based multi-layer-film optical data storage medium has a high transparency and flexibility. The high signal-to-noise ratio remains stable after the structure is bent 1000 times.

Far-field optical superlenses without metal

The spatial resolution in traditional optical microscopy is limited by diffraction. This prevents imaging of features with dimensions smaller than half of the wavelength (λ) of the illumination source. Superlenses have been recently proposed and demonstrated to overcome this issue. However, its implementation often involves complex sample fabrication and lossy metal layers. Alternatively, a superlens without metals can be realized using surface waves as the illumination source at the interface between two dielectrics, at the total internal reflection condition, where one of the dielectrics is doped with a fluorescent material. Non-scanning far-field images with resolution of ∼λ/5 and without the need of any post-processing or image reconstruction can be achieved with this approach.

Reflector Texturing Design of a Thin Film Solar Cell in a Specific Wavelength Range Using Topology Optimization

For a thin film solar cell, proper light trapping is commonly requested for the purpose of increasing the absorbing efficiency in the silicon absorbing layer. This study aims to suggest a design method for a thin film solar cell using topology optimization so that the overall efficiency increases in a specified wavelength range from 700 nm to 800 nm. For the efficient energy translation, extending the wave-path length and raising the efficiency are inevitable. The bottom transparent conducting oxide (TCO) layer shape is designed so that the propagating wave reflects on the surface and it satisfies the total internal reflection condition at the top TCO layer.