Silicon oxide, silicon nitride and silicon oxynitride layers were grown by a PECVD technique. The resulting refractive indices of the layers varied between 1.47 and 1.93. The compositional properties of the layers were analyzed by FTIR and ATR infrared spectroscopy techniques. Comparative investigation of bonding structures for the three different layers was performed. Special attention was given to analyze N-H bond stretching absorption at 3300-3400 cm-1. Quantitative results for hydrogen related bonding concentrations are presented based on IR analysis. An annealing study was performed in order to reduce or eliminate this bonding types. For the annealed samples the N-H bond concentration was strongly reduced as verified by FTIR transmittance and ATR spectroscopic methods. A correlation between the N-H concentration and absorption loss was verified for silicon oxynitride slab waveguides. Moreover, a single mode waveguide with silicon oxynitride core layer was fabricated. Its absorption and insertion loss values were determined by butt-coupling method, resulting in low loss waveguides. © 2003 Elsevier B.V. All rights reserved

In this paper, we report experimental and theoretical investigations on tuning of the surface plasmon-exciton coupling by controlling the plasmonic mode damping, which is defined by the plasmonic layer thickness. The results reveal the formation of plasmon-exciton hybrid state characterized by a tunable Rabi splitting with energies ranging from 0 to 150 meV. Polarization-dependent spectroscopic reflection measurements were employed to probe the dispersion of the coupled system. The transfer matrix method and analytical calculations were used to model the self-assembled J-aggregate/metal multilayer structures in excellent agreement with experimental observations. © 2012 American Physical Society

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 μm. Even smaller devices can be made using submicron-thick Si waveguides. © 2005 IEEE

We have demonstrated slow propagation of surface plasmons on metallic Moiré surfaces. The phase shift at the node of the Moiré surface localizes the propagating surface plasmons and adjacent nodes form weakly coupled plasmonic cavities. Group velocities around v_{g}=0.44c at the center of the coupled cavity band and almost a zero group velocity at the band edges are observed. A tight binding model is used to understand the coupling behavior. Furthermore, the sinusoidally modified amplitude about the node suppresses the radiation losses and reveals a relatively high quality factor (Q=103).

The temperature dependence (15±293 K) of the six Raman-active mode frequencies and linewitdhs in gallium sul®de has been measured in the frequency range from 15 to 380 cm 21. We observed softening and broadening of the optical phonon lines with increasing temperature. Comparison between the experimental data and theories of the shift and broadening of the interlayer and intralayer phonon lines during the heating of the crystal showed that the experimental dependencies can be explained by the contributions from thermal expansion and lattice anharmonicity. The pure-temperature contribution (phonon± phonon coupling) is due to three-and four-phonon processes. q

Figure 1. The normal incidence reflection spectra for three different strain values of 7.5%, 15% and 23% for grating A (main) and no strain, 6.4% and 12.8% for grating B (inset). Abstract-In this study, we demonstrate that periods of metallic gratings on elastomeric substrates can be tuned with external strain and hence are found to control the resonance condition of surface plasmon polaritons [1]. The periods of the gratings are increased up to 25% by the use of applied mechanical strain. The tunability of the elastomeric substrate provides the opportunity to use such gratings as efficient surface enhanced Raman spectroscopy substrates. It's been demonstrated that the Raman signal can be maximized by tuning the period of the elastomeric grating. Tunable Surface Plasmon Resonance on an Elastomeric GratingThe surface plasmon resonance (SPR) phenomena observed on metal surfaces or nanoparticles has been a great interest in several fields of research such as nanoscale photonics and biological sensing. Continuous metallic films possessing a periodic perturbation exhibit strong extinction and scattering spectra when excited at the SPR condition. The challenge of designing effective structures to manipulate plasmonic fields and utilize them in functional devices still remains. In particular, the use of SPR in surface enhanced Raman spectroscopy (SERS) and biological sensing require an intelligent design in order to maximize the plasmonic enhancement. In this regard, the tunability of the SPR wavelength provides flexibility in many plasmonic sensing applications. Flexible designs utilizing electronic [2], ferroelectric [3], or thermal [4] tuning mechanisms are also reported in the literature. Those methods are reversible and can be applied after the plasmonic structure is fabricated. Such a repeatable process can find wide applications in the field of Raman spectroscopy and plasmonic sensing. It was reported that by controlling the geometry of the nanoshells films, the SERS enhancements can be optimized [5]. A repeatable thermal tuning mechanism using silver nanoparticles for achieving a tunable SERS substrate was reported by Lu et al. [6].In this study we use an elastomeric grating structure in order to excite surface plasmon polaritons (SPP) on its metallic surface. We report a way of tuning the SPR by applying mechanical strain on the elastomeric grating structure. The elongation of the elastomer effectively changes the period of the metallic grating. It can be seen that the SPR wavelength also shifts as the external strain changes the period of the elastomeric grating coated with a thin metallic layer.We fabricated two silicone elastomers with gratings on top using two different methods. The first elastomeric grating was generated using holographic lithography with 665 nm period. The elastomeric grating is then obtained using the replication procedure. Note that the thickness of the elastomer is kept around 5 mm. To generate SPP, the PDMS grating is coated with a 55 nm of silver using thermal evaporation. For the ...

Low temperature photoluminescence of GaS single crystals shows three broad emission bands below 2.4 eV. Temperature and excitation light intensity dependencies of these bands reveal that all of them originate from close donor-acceptor pair recombination processes. Temperature dependence of the peak energies of two of these bands in the visible range follow, as expected, the band gap energy shift of GaS. However, the temperature dependence of the peak energy of the third band in the near infrared shows complex behavior by blueshifting at low temperatures followed by a redshift at intermediate temperatures and a second blueshift close to room temperature, which could only be explained via a configuration coordinate model. A simple model calculation indicates that the recombination centers are most likely located at the nearest neighbor lattice or interstitial sites.

Surface-enhanced Raman Scattering (SERS) of rhodamine 6G (R6G) adsorbed on biharmonic metallic grating structures was studied. Biharmonic metallic gratings include two different grating components, one acting as a coupler to excite surface plasmon polaritons (SPP), and the other forming a plasmonic band gap for the propagating SPPs. In the vicinity of the band edges, localized surface plasmons are formed. These localized plasmons strongly enhance the scattering efficiency of the Raman signal emitted on the metallic grating surfaces. It was shown that reproducible Raman scattering enhancement factors of over 10 5 can be achieved by fabricating biharmonic SERS templates using soft nano-imprint technique. We have shown that the SERS activities from these templates are tunable as a function of plasmonic resonance conditions. Similar enhancement factors were also measured for directional emission of photoluminescence. At the wavelengths of the plasmonic absorption peak, directional enhancement by a factor of 30 was deduced for photoluminescence measurements. Wang, "Highly Raman-enhancing substrates based on silver nanoparticle arrays with tunable sub-10 nm gaps," Adv. References and Links