Engineering topics

Premaratne, Malin

Publications and source records attributed to Premaratne, Malin.

4 records

DOE OSTI2016

MoS{sub 2} spaser

We present a comprehensive analysis of a spaser made of a circular shaped highly doped molybdenum disulfide (MoS{sub 2}) resonator. “Spaser” is an acronym for “surface plasmon amplification by stimulated emission of radiation”–a nanoscale source of surface plasmons generated by stimulated emission in a plasmonic resonator which receives energy nonradiatively. By considering localized surface plasmon modes, operation characteristics of the model are analysed, and tunability of the design is demonstrated. We find the optimum geometric and material parameters of the spaser that provides efficient outputs and carryout a comparative analysis with a similar circular spaser made of graphene. Owing to physical and chemical properties of MoS{sub 2} and the active medium, the proposed design delivers efficient outputs in terms of spaser mode energy, operating thresholds, Q-factor, and electric field amplitude. Lower operating thresholds and higher mode energies are notable advantages of the design. Owing to having many superior features to existing similar designs, this MoS{sub 2} spaser may be much suited for applications in nanoplasmonic devices.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

DOE OSTI2015

Multimode analysis of highly tunable, quantum cascade powered, circular graphene spaser

We carried out a detailed analysis of a circular graphene spaser made of a circular graphene flake and a quantum cascade well structure. Owing to unique properties of graphene and quantum cascade well structure, the proposed design shows high mechanical and thermal stability and low optical losses. Additionally, operation characteristics of the model are analysed and tunability of the device is demonstrated. Some advantages of the proposed design include compact size, lower power operation, and the ability to set the operating wavelength over a wide range from Mid-IR to Near-IR. Thus, it can have wide spread applications including designing of ultracompact and ultrafast devices, nanoscopy and biomedical applications.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

DOE OSTI2015

Optically resonant magneto-electric cubic nanoantennas for ultra-directional light scattering

Cubic dielectric nanoparticles are promising candidates for futuristic low-loss, ultra-compact, nanophotonic applications owing to their larger optical coefficients, greater packing density, and relative ease of fabrication as compared to spherical nanoparticles; besides possessing negligible heating at nanoscale in contrast to their metallic counterparts. Here, we present the first theoretical demonstration of azimuthally symmetric, ultra-directional Kerker's-type scattering of simple dielectric nanocubes in visible and near-infrared regions via simultaneous excitation and interference of optically induced electric- and magnetic-resonances up to quadrupolar modes. Unidirectional forward-scattering by individual nanocubes is observed at the first generalized-Kerker's condition for backward-scattering suppression, having equal electric- and magnetic-dipolar responses. Both directionality and magnitude of these unidirectional-scattering patterns get enhanced where matching electric- and magnetic-quadrupolar responses spectrally overlap. While preserving azimuthal-symmetry and backscattering suppression, a nanocube homodimer provides further directionality improvement for increasing interparticle gap, but with reduced main-lobe magnitude due to emergence of side-scattering lobes from diffraction-grating effect. We thoroughly investigate the influence of interparticle gap on scattering patterns and propose optimal range of gap for minimizing side-scattering lobes. Besides suppressing undesired side-lobes, significant enhancement in scattering magnitude and directionality is attained with increasing number of nanocubes forming a linear chain. Optimal directionality, i.e., the narrowest main-scattering lobe, is found at the wavelength of interfering quadrupolar resonances; whereas the largest main-lobe magnitude is observed at the wavelength satisfying the first Kerker's condition. These unique optical properties of dielectric nanocubes thus can revolutionize their applications at visible and near-infrared regions in the fields of nanoantennas, nanolasers, photovoltaics, and even in biomedicine.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

DOE OSTI2013

Light focusing using epsilon-near-zero metamaterials

We present a strategy of focusing light using epsilon-near-zero metamaterials with embedded dielectric cylinder. The focusing mechanism is analytically investigated, and its accuracy is substantiated by rigorous full-wave simulations. It is found that the focusing intensity is highly depend on the embedded medium and its size, and the magnetic field amplitude of the focused beam itself can reach as high as 98.2 times the incident field. Owing to its versatility, the proposed light focusing system is sure to find applications in fields such as bio-sensing and in nonlinear optics.

36 MATERIALS SCIENCE↗