In conventional lasers, the optical cavity that confines photons also determines essential characteristics of lasing modes such as wavelength, emission pattern, directivity, and polarization. random which do not have mirrors or a well-defined cavity, light is confined within gain medium by means multiple scattering. The sharp peaks in spectra semiconductor powders, first observed 1999, has therefore lead to an intense debate about nature these so-called lasers with resonant feedback. We...

We analyze the absorption of solar radiation by silicon nanowire arrays, which are being considered for photovoltaic applications.These structures have been shown to enhanced compared with thin films, however mechanism responsible this is not understood.Using a new, semi-analytic model, we show that can be attributed few modes array, couple well incident light, overlap nanowires, and exhibit strong Fabry-Pérot resonances.For some wavelengths further slow light effects.We study evolution...

We consider band structure calculations of two-dimensional photonic crystals treated as stacks one-dimensional gratings. The gratings are characterized by their plane wave scattering matrices, the calculation which is well established. These matrices then used in combination with Bloch's theorem to determine a crystal from solution an eigenvalue problem. Computationally beneficial simplifications eigenproblem for symmetric lattices derived, spectrum classified, and, at long wavelengths,...

We present detailed experimental and numerical studies of random lasing in weakly scattering systems. The interference scattered light, which is weak the passive systems, greatly enhanced presence high gain, providing coherent resonant feedback for lasing. modes are confined vicinity pumped volume due to absorption emitted light outside it. In ballistic regime where size gain less than mean free path, oscillation occurs along direction most extended, producing directional laser output....

Using the exact theory of multipole expansions, we construct two-dimensional Green's function for photonic crystals, consisting a finite number circular cylinders infinite length. From this function, compute local density states (LDOS), showing how crystal affects radiation properties an fluorescent line source embedded in it. For frequencies within band gap crystal, LDOS decreases exponentially inside crystal; bands, find "hot" and "cold" spots. Our method can be extended to three...

We discuss density of states functions for photonic crystals, in the context two-dimensional problem arrays cylinders arbitrary cross section. introduce mutual (MDOS), and show that this function can be used to calculate both local (LDOS), which gives position information emission radiation from spectral (SDOS), angular information. establish connection between MDOS, LDOS, SDOS conventional states, depends only on frequency. relate all four band structure propagating within crystal, give...

We present a formulation for wave propagation and scattering through stacked gratings comprising metallic dielectric cylinders. By modeling photonic crystal as grating stack of this type, we thus formulate an efficient accurate method calculations that allows us to calculate reflection transmission matrices. The may contain arbitrary number gratings, provided each has common period. uses Green's function approach based on lattice sums obtain the matrices layer, it couples these layers...

We study wave propagation in mixed, 1D disordered stacks of alternating right- and left-handed layers reveal that the introduction metamaterials substantially suppresses Anderson localization. At long wavelengths, localization length mixed is orders magnitude larger than for normal structures, proportional to sixth power wavelength, contrast usual quadratic wavelength dependence systems. Suppression also exemplified long-wavelength resonances which largely disappear when materials are introduced.

We present a rigorous Bloch mode scattering matrix method for modeling two-dimensional photonic crystal structures and discuss the formal properties of formulation. Reciprocity energy conservation considerations lead to modal orthogonality relations normalization, both which are required calculations in inhomogeneous media. Relations derived studying propagation modes through structures, reflection transmission these at interfaces with other structures.

The effect of the microstructure on transversely coupled laser light into core a photonic crystal fiber is investigated. Computational two-dimensional modeling and direct experimental measurements indicate that there exist angles positions microstructure, relative to launched beam, preferentially couple core. implications these observations long period fiber-Bragg grating fabrication in fibers are discussed.

A finite element-based modal formulation of diffraction a plane wave by an absorbing photonic crystal slab arbitrary geometry is developed for photovoltaic applications. The semianalytic approach allows efficient and accurate calculation the absorption array with complex unit cell. This gives direct physical insight into mechanism in such structures, which can be used to enhance absorption. verification validation this applied silicon nanowire array, efficiency accuracy method demonstrated....

Solar cell designs based on disordered nanostructures tend to have higher efficiencies than structures with uniform absorbers, though the reason is poorly understood. To resolve this, we use a semi-analytic approach determine physical mechanism leading enhanced efficiency in arrays containing nanowires variety of radii. We our findings systematically design that outperform randomly composed structures. An ultimate 23.75% achieved an array 30% silicon, increase almost 10% over homogeneous...

The electromagnetic transmittance of disordered two-dimensional photonic crystals composed circular cylinders is investigated as a function wavelength and polarization. At short wavelengths, the shows band structure similar to that found in optical absorption spectrum amorphous semiconductors, with impurity states increasingly appearing on long side gaps degree disorder increased. In long-wavelength limit, Anderson localization waves found, provided not so large random crystal can be viewed...

In lossless periodic media, the concept of group velocity is fundamental to study propagation dynamics. When spatially averaged, numerically equivalent energy velocity, defined as ratio flux density modal fields. However, in lossy diverges from velocity. Here, we define a field which remains equal complex homogeneous and media. The definition extends more general situation fields that exhibit spatial or temporal decay due elements Bragg reflection effects. Our simple expression relies on...

We study the propagation and localization of classical waves in one-dimensional disordered structures composed alternating layers left- right-handed materials (mixed stacks) compare them with different same material (homogeneous stacks). For weakly scattering layers, we have developed an effective analytical approach calculated transmission length within a wide range input parameters. This enables us to describe, unified way, localized ballistic regimes as well crossover between them. When...

We investigate the optical properties of silicon nanohole arrays for application in photovoltaic cells terms modes within structure.We highlight three types modes: fundamental modes, important at long wavelengths; guided resonance which enhance absorption wavelengths where intrinsic is low; and channeling suppress front-surface reflection.We use this understanding to explain why parameters optimized occur specific ranges even as thickness varied.

Nanowire arrays exhibit efficient light coupling and strong trapping, making them well suited to solar cell applications. The processes that contribute their absorption are interrelated highly dispersive, so the only current method of optimizing is by intensive numerical calculations. We present an alternative depends solely on wavelength-dependent refractive indices constituent materials. choose each array parameter such number modes propagating away from absorber minimized, while resonant...

The effects of disorder in the geometry and refractive index on transmittance two-dimensional photonic crystals composed dielectric circular cylinders are considered, including randomness radii, positions cylinder centers, thickness each layer crystal. combinations different types strong also considered. localization homogenization properties disordered investigated. Analytical expressions for length form integrals presented both polarizations. It is shown numerically that slope exponential...

A method is developed to calculate electromagnetic properties of arrays metallic and dielectric cylinders. It incorporates exploits cylindrical boundary conditions Rayleigh identities for efficient, high-accuracy calculation scattering off individual layers that are stacked into using matrices. The enables absorption, dispersion, randomness be incorporated efficiently, reproduces known results with vastly improved speed accuracy. used demonstrate existence states introduced photonic band...

Comprehensive theoretical and numerical studies of the effects dispersion absorption on Anderson localization classical waves in weakly disordered, one-dimensional stacks composed dispersive metamaterials normal materials are presented. An asymptotic analysis for studying is developed. It shown that random entirely either metamaterial or dielectric layers completely suppressed at frequencies where magnetic permeability permittivity zero. In mixed alternating with disorder present...

A numerical implementation and generalized conservation properties of a formulation for calculating wave propagation through stacked gratings comprising metallic dielectric cylinders are presented. The basic the method was given in companion paper [J. Opt. Soc. Am. A. 17, 2165 (2000)]. Here, details discussed illustrated ensemble average strongly scattering structure with refractive index radius disorder. Also presented comprehensive treatment energy phase relations, as well reciprocity.

This is a review of some recent (mostly ours) results on Anderson localization light and electron waves in complex disordered systems, including: (i) left-handed metamaterials, (ii) magnetoactive optical structures, (iii) graphene superlattices, (iv) nonlinear dielectric media. First, we demonstrate that metamaterials can significantly suppress lead to an anomalously enhanced transmission. suppression essential at the long-wavelength limit case normal incidence, specific angles oblique...

Abstract The two-dimensional Green tensor for photonic crystals, consisting of clusters circular cylinders infinite length, is constructed using the exact theory multipole expansions. On basis this tensor, local density states both polarizations calculated, showing how depends on position inside crystal. We include results with a waveguide, obtained by removing line cylinders, and cavity, forming localized defect.

We consider the modes of coupled photonic crystal waveguides. find that fundamental these structures can be either even or odd, in contrast with behavior conventional waveguides, which mode is always even. explain this finding using an asymptotic model valid for long wavelengths.