An elastomeric grating coupler

We report on a novel nondestructive and reversible method for coupling free space light to planar optical waveguides. In this method, an elastomeric grating is used to produce an effective refractive index modulation on the surface of the optical waveguide. The external elastomeric grating binds to the surface of the waveguide with van der Waals forces and makes conformal contact without any applied pressure. As a demonstration of the feasibility of the approach, we use it to measure the refractive index of a silicon oxynitride film. This technique is nondestructive, reversible, low cost and can easily be applied to the characterization of optical materials for integrated optics

Visible Photoluminescence from Low Temperature deposited hydrogenated amorphous silicon nitride

Cataloged from PDF version of article.Hydrogenated amorphous silicon nitride (a-SiNx:H) samples have been prepared by plasma enhanced chemical vapor deposition (PECVD) using a mixture of silane (Sill4), nitrogen and ammonia (NH3). Most films exhibit visible photoluminescence (PL) and some emit strong PL after annealing. While films grown without NH 3 exhibit PL in the deep red, those grown with NH 3 show PL in the green. The PL properties of these films with no oxygen (O) content are similar to those of silicon oxide (SiO x) films and porous Si. Using infrared and X-ray Photoelectron Spectroscopy, we suggest that PL from a-SiNx:H films originate from Si clusters which form during PECVD and crystallize upon annealing. We propose that the presence of O is not necessary for efficient PL

Price Promotion for Emotional Impact

Managers and academics often think of price promotions merely as incentives that entice consumers to accept offers that they might not have considered otherwise. Yet the prospect of paying a lower price for a product of given quality can also discourage deliberation, in a sense "dumbing down" the purchase encounter by making it less consequential. The authors examine this possibility in a dual-system theory of consumer behavior. Specifically, they argue that price promotion lowers a consumer's motivation to exert mental effort, in which case purchase decisions are guided less by extensive information processing and more by a quicker, easier, strong conditioner of preference: affect. Field data from a large daily deal company and four controlled experiments support this idea and document its implications primarily for product choice, in turn providing insight into the form and cause of brand switching that manufacturers and retailers can leverage to improve the allocation of promotional budgets and category management

The Conflict Resolution and Counterterrorism Dilemma: Turkey Faces its Kurdish Question

Cataloged from PDF version of article.This article considers the relationship between two processes-conflict resolution and counterterrorism-which conceptually share many common points, yet in practice do not necessarily proceed together easily towards a common goal. Considering particular cases of ethnic conflict in which terrorist factions exist, the article argues that while neither conflict resolution nor counterterrorism alone can adequately address the problem, simultaneously conducting both must keep in mind the processes' inherent differences and avoid excessive prioritizing of one over the other. By exploring recent Turkish governmental initiatives to address the Kurdish question, the article attempts to provide an outline for how to successfully cope with the two processes simultaneously. © Taylor & Francis Group, LLC

Low temperature photoluminescence spectra of InS single crystals

Cataloged from PDF version of article.Photoluminescence (PL) spectra of InS were investigated in the wavelength region 477.5–860 nm and in the temperature range 8.5–293 K. We observed three PL bands centered at 605 nm (A-band), 626 nm (B-band) and 820 nm (C-band). The A- and B-bands are due to radiative transitions from the donor level at 0.01 eV below the bottom of the conduction band to the valence band and from the donor level at 0.06 eV below the bottom of the conduction band to the acceptor level 0.12 eV above the top of the valence band, respectively. The proposed energy-level scheme allows us to interpret the recombination processes in InS single crystals. Copyright © 1997 Published by Elsevier Ltd

A Comparative Passivation Study for InAs/GaSb Pin Superlattice Photodetectors

Cataloged from PDF version of article.In the quest to find ever better passivation techniques for infrared photodetectors, we explore several passivation layers using atomic layer deposition (ALD). We compare the impact of these layers on detectors fabricated under same conditions. We use ALD deposited Al2O3, HfO2, TiO2, ZnO, plasma enhanced chemical vapor deposition deposited SiO2, Si3N4, and sulfur containing octadecanethiol self assembled monolayer passivation layers on InAs/GaSb p-i-n superlattice diodes with an average cutoff wavelength of 5.1 mu m. Passivated and unpassivated photodetectors compared for their electrical performances

Microcavity effects in the photoluminescence of hydrogenated amorphous silicon nitride

Fabry-Perot microcavities are used for the alteration of photoluminescence in hydrogenated amorphous silicon nitride grown with and without ammonia. The photoluminescence is red-near-infrared for the samples grown without ammonia, and blue-green far the samples grown with ammonia. In the Fabry-Perot microcavities, the amplitude of the photoluminescence is enhanced, while its linewidth is reduced with respect to the bulk hydrogenated amorphous silicon nitride. The microcavity was realized by a metallic back mirror and a hydrogenated amorphous silicon nitride - air or a metallic front mirror. The transmittance, reflectance, and absorbance spectra were also measured and calculated. The calculated spectra agree well with the experimental spectra. The hydrogenated amorphous silicon nitride microcavity has potential for becoming a versatile silicon based optoelectronic device such as a colot flat panel display, a resonant cavity enhanced light emitting diode, or a laser

A Compact Silicon-on-insulator Polarization Splitter

Cataloged from PDF version of article.A compact directional coupler-based polarization splitter is designed and realized using silicon-on-insulator (SOI) waveguides. Even though silicon does not have any material birefringence, the high index contrast obtained in the SOI platform and reduced waveguide dimensions makes it possible to induce significant birefringence. Polarization splitting is achieved by making use of this geometry-induced birefringence. In this work, we demonstrate polarization splitting in devices as short as 120 gm. Even smaller devices can be made using submicron-thick Si waveguides

Critical coupling in plasmonic resonator arrays

Cataloged from PDF version of article.We report critical coupling of electromagnetic waves to plasmonic cavity arrays fabricated on Moire surfaces. Dark field plasmon microscopy imaging and polarization dependent spectroscopic reflection measurements reveal the critical coupling conditions of the cavities. The critical coupling conditions depend on the superperiod of the Moire surface, which also defines the coupling between the cavities. Complete transfer of the incident power can be achieved for traveling wave plasmonic resonators, which have a relatively short superperiod. When the superperiod of the resonators increases, the coupled resonators become isolated standing wave resonators in which complete transfer of the incident power is not possible. Analytical and finite difference time domain calculations support the experimental observations. (C) 2011 Optical Society of Americ

Grating based plasmonic band gap cavities

Cataloged from PDF version of article.We report on a comparative study of grating based plasmonic band gap cavities. Numerically, we calculate the quality factors of the cavities based on three types of grating surfaces; uniform, biharmonic and Moiré surfaces. We show that for biharmonic band gap cavities, the radiation loss can be suppressed by removing the additional grating component in the cavity region. Due to the gradual change of the surface profile in the cavity region, Moiré type surfaces support cavity modes with higher quality factors. Experimentally, we demonstrate the existence of plasmonic cavities based on uniform gratings. Effective index perturbation and cavity geometries are obtained by additional dielectric loading. Quality factor of 85 is obtained from the measured band structure of the cavity. © 2009 Optical Society of America