Search results for "Photonic Crystal"

Free spectral range enlargement by selective suppression of optical modes in photonic crystal L7 microcavities

2015

We show an enlargement in the free spectral range (FSR) of the emission spectra of a L7 photonic crystal microcavity (PCM). The FSR enlargement is achieved by the selective modal suppression of the second cavity mode. The selective suppression is made by introducing two nano-inclusions in specific sites within the defect region that forms the cavity. We have demonstrated the suppression of the second mode of the L7-PCM, and a significant increase in the FSR of the fundamental mode. The method provides an alternative to engineer the modal structure of a photonic crystal microcavity. The large FSR-value might improve the emission properties of light sources based on photonic crystal structure…

Designing a photonic crystal fibre with flattened chromatic dispersion

1999

Using a full-vector modal method, the authors have identified a region of nearly zero flattened chromatic dispersion in a specially designed photonic crystal fibre. The approach permits an accurate control of the dispersion features of these fibres in terms of their structural parameters.

In situ tuning of a photonic band gap with laser pulses

2008

We report on light-induced optical tuning of colloidal photonic crystals doped with gold nanoparticles (Au-nps). By resonantly exciting the Au-np surface plasmon absorption with picosecond pulses at 0.53 micron in a standard pump-probe setup, we observed permanent changes in the stop band resonance around 1.7 micron, with blue wavelength shifts as large as 30 nm and associated to a nanoparticle reshaping. Fine tuning was achieved by controlling either the pulse energy or the irradiation time.

Simulation of surface-modified porous silicon photonic crystals for biosensing applications

2012

In this work realistic biosensing structures based on the integration of porous silicon photonic crystals with polymer coating technology are presented. Microcavities and rugate filters are chosen as the photonic crystal configuration. The deposition of a polymer layer on the pore walls of these structures is proposed to improve the selectivity and sensitivity of the sensing function. A complete effective refractive index model including the polymer layer, the target and external effects like silicon oxidation has been developed in order to accurately simulate the structures. It is expected that the proposed structures could be used as low cost, highly integrated and highly sensitive biolog…

Creating Defined 3-D Defects Inside an Opaline Ormocer® Matrix with Two-Photon Lithography

2007

The creation of defined structures inside a synthetic opal is a key step toward applications in optics, where control of the propagation of light inside a photonic crystal is necessary. In a previous paper, we described the nanostructuring of Ormocer® to form inverse opals (Lange et al., Macromol. Rapid Commun. 2006, 27, 1746). Here, we report an application for this robust replica process in which defects can be directly produced within the PC by two-photon lithography. The holes of an inverse opal structure are first filled with a resin of similar refractive index. In this transparent material, polymerization can be initiated at defined places via two-photon lithography. After removal of …

Macromol. Chem. Phys. 21/2013

2013

Hydrogel films engineered in a mesoscopically ordered structure and responsive to ethanol vapors

2014

Abstract Responsive hydrogels filling the interstitial spaces of photonic crystals can form mesoscopically structured materials, which exhibit reversible shifts in the Bragg diffracted light as a response of environmental changes. These materials can be used to generate chemical or biochemical sensors. The present work reports on the synthesis and characterization of ethanol responsive hydrogels that can be used in the design of novel breathalyzers. The dynamic mechanical behavior of the macroscopic hydrogels and their swelling features in the presence of different liquids or vapors have been investigated to orientate the choice of the best responsive material and curing process. The swelli…

High Optical Quality Films of Liquid Crystalline Cellulose Derivatives in Acrylates

2013

Electrodeposition of ZnO nanorods on opaline replica as hierarchically structured systems

2011

We present a new method to prepare hierarchical structures by using ZnO replica and ZnO-coated PMMA opals as electrodes in an electrodeposition process of ZnO nanorods. Depending on the approach the nanorods can be either grown exclusively on top of the replica or inside the replica structures. Therefore two types of systems are accessible: 3D photonic crystals with a hierarchically structured surface consisting of nanorods and macroporous ZnO structures with an increased surface area.

Guiding and reflecting light by boundary material

2003

We study effects of finite height and surrounding material on photonic crystal slabs of one- and two-dimensional photonic crystals with a pseudo-spectral method and finite difference time domain simulation methods. The band gap is shown to be strongly modified by the boundary material. As an application we suggest reflection and guiding of light by patterning the material on top/below the slab.