Light Intensity Enhancement Inside the Grooves of Metallic Grating

Light absorption inside the grooves of metallic gratings filled with a semiconductor material can be improved by means of the electric field enhancement. To this end, the influence of grating dimensions in the electric field spectral behavior is theoretically investigated. Two conditions of cavity resonance have been analyzed separately: (1) for TE polarization (electric field parallel to the grooves) and (2) for TM polarization (magnetic field parallel to the grooves). When dimensions are chosen according to the first condition, the enhancement of TE fields is found to increase with the height-to-width ratio, and it is accompanied with a decrease in the bandwidth. The same enhancement levels can be achieved for TM fields if the second condition holds, provided that the period-to-width ratio is large enough. The simultaneous enhancement of TE and TM fields, based on a condition of surface resonance excitation, can also be accomplished. In this case, the TM response is very sensitive to changes in groove depth and width

Light trapping within the grooves of 1D diffraction gratings under monochromatic and sunlight illumination

The Rayleigh-Modal method is used to calculate the electromagnetic field within the grooves of a perfectly conducting, rectangular-shaped 1D diffraction grating. An \emph{enhancement coefficient} ($\eta$) is introduced in order to quantify such an energy concentration. Accordingly, $\eta >$1 means that the amount of electromagnetic energy present within the grooves is larger than that one will have, over the same volume, if the diffraction grating is replaced by a perfectly reflecting mirror. The results in this paper show that $\eta$ can be as large as several decades at certain, often narrow, ranges of wavelengths. However, it reduces to approximately 20% under sunlight illumination. In this latter case, such values are achieved when the \textit{optical spacing} between the grooves $dn$ is greater than 500 nm, where $d$ is the groove spacing and $n$ is the refractive index of the substance within the grooves. For $dn$ smaller than 500 nm the enhancement coefficient turns negligibly small.Comment: This paper contains 11 pages and 4 figures, and will be published elsewher

Low-injection behaviour of a solar cell with a metallic grating back-reflector

Recent studies have dealt with the possibility of increasing light absorption by using the so-called electric field enhancement taking place within the grooves of metallic gratings. In order to evaluate the potential improvements derived from the absorption increase, we employ a simplified model to analyze the low-injection behaviour of a solar cell with a metallic grating back-reflector

Light trapping by means of electric field enhancement in metallic grantings

The enhancement of the electromagnetic field within the grooves of a metallic diffraction grating is analyzed. A perfect conductor, rectangular-shaped diffraction grating is assumed, therefore, the field enhancement analyzed in this work is due to resonances caused by the structure itself, and not to the so-called surface-plasmon resonances which are observed to be influenced by metal properties as well. The modal approach has been employed for calculations. Basically, the squared amplitude of the electric field within the grooves is calculated as a function of the wavelength of the incident light. Similarly, the behaviour of the structure when exposed to a conical bundle of light is also analyzed. The present results show that a field intensity enhancement of the order of 100 is achievable. However, the spectral width of the resonances decrease with increasing enhancement as is expecte

Many-Body Effects in Atomic-Collision Cascades

Molecular-dynamics simulations have been used to identify two cooperative atom-ejection mechanisms which increase sputtering yield. Their effects are analogous to the "thermal spike," "shock wave," and "reduced binding energy" sputtering mechanisms. They are examples of nonlinear, many-body effects in cascades which go beyond collisions between randomly moving particles.This work was supported by a Special Opportunity Cxrant from the Office of Naval Research, and by the Foundation Research Program of the Naval Postgraduate School

Influence of electronic energy losses on atom ejection processes

Two independent computer simulations models establish that when ions bombard solid targets, electronic energy losses by atoms within the collision cascade have greater influence on the ejected atom yield than the ion's electronic losses. This conclusion is independent of the ion's mass or energy, or the mass ratio.This investigation was supported by a Special Research Opportunity Grant from the Office of Naval Research and by the Foundation Research Program of the Naval Postgraduate School

Dependence of atom ejection on electronic energy loss

This paper extends previous theoretical models to emphasize the influence of electronic energy losses upon the ejection of atoms by bombarding ions. This sensitivity of the sputtering yield to inelastic energy losses was first observed in computer simulations of sputtering. The theoretical analysis supports the simulation-derived conclusion that the total yield is much more sensitive to electronic energy losses by the atoms than to electronic energy losses of the bombarding ions, even when the ion is much lighter than the target atoms.Special Research Opportunity Grant from the U.S. Office of Naval Research, Department of the Navy, and by the Foundation Research Program of the Naval Postgraduate School (Monterey, Ca.)Approved for public release; distribution is unlimited

Efecto de la excentricidad de la órbita electrónica del átomo de H en el calculo del poder de frenado en la colisión de un protón con un átomo de H(1s), mediante el método CTMC

Se aplicó el método de trayectorias clásicas monte carlo (CTMC) al cálculo de las secciones eficaces de ionización, captura, excitación y stopping total de la colisión de un protón con un átomo de hidrógeno. Se utilizó las ecuaciones del movimiento planetario de Kepler para representar el electrón 1s en el campo Coulombiano del protón y se generaron las condiciones iniciales del electrón mediante la función de distribución microcanónica. Se consideraron las excentricidades ε=0.75, ε=0.001 y ε= aleatoria (en el rango [0,1]) para el cálculo de las secciones eficaces y stopping total. Los resultados muestran que las secciones eficaces para ε=0.75 y ε=aleatoria coinciden entre sí, no así para ε=0.001; mientras que para el stopping total los resultados reproducen bien los resultados experimentales de energías intermedias y altas.The Classical trajectory Monte Carlo Method (CTMC) is applied to the calculation of ionization, excitation, charge transfer and Stopping cross sections in the proton-Hydrogen collision process. Kepler equations for planetary motion are used to resemble the 1s electron in the proton Coulombic field and the electron initial conditions were generated by a microcanonical distribution function. Fixed eccentricities ε=0.75, ε=0.001 and random ([0,1] range) eccentricities were used for the calculation of cross sections and stopping. The results shows that the ε=0.75 y ε=random cross sections coincide between them, that is not the case for the ε=0.001 distribution; also the total stopping results are in good agreement with the experimental data in the high and intermediate energy range.Fil: Rodriguez Aguirre, Juan Manuel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Instituto de Modelado e Innovación Tecnológica. Universidad Nacional del Nordeste. Facultad de Ciencias Exactas Naturales y Agrimensura. Instituto de Modelado e Innovación Tecnológica; ArgentinaFil: Custidiano, Ernesto Ramon. Universidad Nacional del Nordeste. Facultad de Ciencias Exactas y Naturales y Agrimensura; ArgentinaFil: Jakas, Mario M.. Universidad de La Laguna; Españ