Surface Plasmon Polaritons: Guided-wave Devices and Applications

The prospect of controlling the interaction of light with matter at nanoscale has been widely studied in recent years, and entails characterizing optical and optoelectronic devices at resolution higher than the diffraction limit. One technique that allows localization of light to sub-wavelength dimensions is through the use of surface plasmon polaritons (SPPs) wherein the interaction of light with free electrons on a metal surface can lead to a bound surface electromagnetic field that is confined to deep sub-wavelength dimensions. Studies based on SPPs merged with the field of nanotechnology have resulted in novel imaging technologies, nonlinear and quantum-optical devices and the ability to design materials with unusual electromagnetic properties with potential applications ranging from enhancing the efficiency of photovoltaic devices to detection of bio-molecules at ultra-small concentrations. Here we report the design of nanophotonic devices based on SPP waveguide structures that would act as a true counterpart to today’s electronic devices, providing orders of increase in data speeds while maintaining nanoscale dimensions. The devices are based on metal-dielectric-metal (MDM) waveguide structures composed of Ag/SiO2/Ag heterostructure that utilizes interference effect within multiple intersecting plasmonic waveguides. We have explored guided-wave devices such as L and T-bends, 4-way-splitters and 2x2-networked structures, wherein by altering the device geometry one can tune its operating frequency, and by changing the angle of incidence one can switch these devices between ON/OFF states. We plan to fabricate and experimentally characterize these devices for applications in color routing, directional filters and optical switches. We discuss preliminary design rules and constraints based on results obtained from finite-difference-time-domain simulations

Band flipping and bandgap closing in a photonic crystal ring and its applications

The size of the bandgap in a photonic crystal ring is typically intuitively considered to monotonically grow as the modulation amplitude of the grating increases, causing increasingly large frequency splittings between the 'dielectric' and 'air' bands. In contrast, here we report that as the modulation amplitude in a photonic crystal ring increases, the bandgap does not simply increase monotonically. Instead, after the initial increase, the bandgap closes and then reopens again with the dielectric band and the air bands flipped in energy. The air and dielectric band edges are degenerate at the bandgap closing point. We demonstrate this behavior experimentally in silicon nitride photonic crystal microrings, where we show that the bandgap is closed to within the linewidth of the optical cavity mode, whose quality factor remains unperturbed with a value $\approx$ 1$\times$10$^6$ (i.e., linewidth of 2 pm). Moreover, through finite-element simulations, we show that such bandgap closing and band flipping phenomena exist in a variety of photonic crystal rings with varying units cell geometries and cladding layers. At the bandgap closing point, the two standing wave modes with a degenerate frequency are particularly promising for single-frequency lasing applications. Along this line, we propose a compact self-injection locking scheme that integrates many core functionalities in one photonic crystal ring. Additionally, the single-frequency lasing might be applicable to DFB lasers to increase their manufacturing yield.Comment: 7 pages, 4 figure

India

This article surveys significant legal developments in India during the year 2014

The anisotropic quasi-static permittivity of single-crystal β-Ga\u3csub\u3e2\u3c/sub\u3eO\u3csub\u3e3\u3c/sub\u3e measured by terahertz spectroscopy

The quasi-static anisotropic permittivity parameters of electrically insulating beta gallium oxide (β-Ga2O3) were determined by terahertz spectroscopy. Polarization-resolved frequency domain spectroscopy in the spectral range from 200 GHz to 1 THz was carried out on bulk crystals along different orientations. Principal directions for permittivity were determined along crystallographic axes c and b and reciprocal lattice direction a*. No significant frequency dispersion in the real part of dielectric permittivity was observed in the measured spectral range. Our results are in excellent agreement with recent radio frequency capacitance measurements as well as with extrapolations from recent infrared measurements of phonon mode and high-frequency contributions and close the knowledge gap for these parameters in the terahertz spectral range. Our results are important for applications of β-Ga2O3 in high-frequency electronic devices

Active Terahertz Devices Based on Hybrid Lead-Halide Perovskites

We demonstrate the use of organic-inorganic lead-halide perovskites to create active terahertz (THz) devices. Specifically, we use a series of two-dimensional hybrid lead halide perovskites to selectively modulate the THz transmission properties. The devices require deposition of the perovskite directly onto a silicon substrate, but allow for control of THz transmission properties using a simple halogen lamp and a set of color filters

Supplement 1: Hiding multi-level multi-color images in terahertz metasurfaces

Supplementary Information Originally published in Optica on 20 December 2016 (optica-3-12-1466