Search results for "Photonic Crystal"

Light Propagation in Heterogeneous Opal-Based Photonic Crystals

2006

Ballistic light propagation in the heterogeneous photonic crystals based on the thin triple-film opal have been studied in the wavelength range of low order photonic bandgaps. Since the scattered light experiences the diffraction attenuation, the spectra and the angle diagrams of the transmitted and forward scattered light have been used to identify the effect of heterostructuring.

Artificially inscribed defects in opal photonic crystals

2005

Opals are three-dimensional photonic crystals, self-assembled from dielectric spherical beads into a face-centered cubic lattice. By introducing intentional defects in the crystal lattice, one modifies features such as spontaneous emission and the directionality of diffracted light. We here present a method for the artificial introduction of a lattice of such intentional defects in self-assembled poly(methyl methacrylate) (PMMA) photonic crystals by means of electron beam lithography. The inscribed defects are of the size of an individual bead, providing a broad spectral range between adjacent resonance peaks. This opens for devices with single line transmission in the photonic band gap, as…

Spatial soliton formation in photonic crystal fibers

2003

We demonstrate the existence of spatial soliton solutions in photonic crystal fibers (PCF's). These guided localized nonlinear waves appear as a result of the balance between the linear and nonlinear diffraction properties of the inhomogeneous photonic crystal cladding. The spatial soliton is realized self-consistently as the fundamental mode of the effective fiber defined simultaneously by the PCF linear and the self-induced nonlinear refractive indices. It is also shown that the photonic crystal cladding is able to stabilize these solutions, which would be unstable otherwise if the medium was entirely homogeneous.

Acoustically tunable photonic band gap structures

2005

We discuss the formation of a tunable one-dimensional photonic band gap structure through the modulation of the resonance frequency of an optical microcavity by a surface acoustic wave (SAW). The microcavity consists of a λ/2 GaAs layer bounded by AlAs/GaAs Bragg mirrors. The SAW periodically modulates the optical thickness of the cavity layer, leading to a light dispersion relation folded within a mini-Brillouin zone (MBZ) defined by |k x |≤ π/λ SAW (k x denotes the photon wave vector component along the SAW propagation direction x-with-caret). In reflection and diffraction experiments, we observe photon modes bounding the gaps in the center and at the boundary of the MBZ as well as a reno…

Redox-Tunable Defects in Colloidal Photonic Crystals

2005

Sub-wavelength imaging of light confinement and propagation in SOI based photonic crystal devices

2006

A light source is coupled into photonic crystal devices and a near field optical probe is used to observe the electromagnetic field propagation and distribution at a sub-wavelength scale. Bloch modes are clearly observed.

Quasi-Normal Frequencies in Open Cavities: An Application to Photonic Crystals

2005

The electromagnetic field in an optical open cavity is analyzed in the framework of the Quasi-Normal Modes theory. The role of the complex quasi-normal frequencies in the transmission coefficient and their link with the density of quasi-modes function is clarified. An application to a quarter-wave symmetric one-dimensional photonic crystals is discussed to illustrate the usefulness and the meaning of our results.

Second quantization and atomic spontaneous emission inside one-dimensional photonic crystals via a quasinormal-modes approach

2004

An extension of the second quantization scheme based on the quasinormal-modes theory to one-dimensional photonic band gap (PBG) structures is discussed. Such structures, treated as double open optical cavities, are studied as part of a compound closed system including the electromagnetic radiative external bath. The electromagnetic field inside the photonic crystal is successfully represented by a new class of modes called quasinormal modes. Starting from this representation we introduce the Feynman's propagator to calculate the decay rate of a dipole inside a PBG structure, related to the density of modes, in the presence of the vacuum fluctuations outside the one-dimensional cavity.

Enhanced resonant force between two entangled identical atoms in a photonic crystal

2013

We consider the resonant interaction energy and force between two identical atoms, one in an excited state and the other in the ground state, placed inside a photonic crystal. The atoms, having the same orientation of their dipole moment, are supposed prepared in their symmetrical state and interact with the quantum electromagnetic field. We consider two specific models of photonic crystals: a one-dimensional model and an isotropic model. We show that in both cases the resonant interatomic force can be strongly enhanced by the presence of the photonic crystal, as a consequence of the modified dispersion relation and density of states, in particular if the transition frequency of the atoms i…

Opals infiltrated with a stimuli-responsive hydrogel for ethanol vapor sensing

2013

We report on a novel class of optical materials for ethanol vapor sensing, based on polystyrene opals infiltrated with an innovative stimuli responsive hydrogel. We describe the fabrication process of the bare polystyrene opals and their subsequent infiltration. The optical characterization of the photonic crystal templates was performed to prove the good quality of the samples. Measurements on the infiltrated opals showed that the transmission spectra in the visible range strongly change at varying concentrations of ethanol vapor. The fabricated structures show a linear optical response in the visible range, for high values of ethanol concentration.