Absorption In Photonic Crystals Research Articles

Selective Absorption of Photonic Crystal with Graphene

Selective absorption of photonic crystal with graphene is studied. The Photonic Crystal at THz regime with permittivity 4.2 is designed and validated with rigorous coupled-wave analysis method (RCWA) and finite element method (FEM). The selective absorption is achieved by combining the Photonic Crystal with Graphene. The selective absorption is explained with Fano resonance fitting method.

Inhibition of two-photon absorption due to dipole–dipole interaction in nanoparticles

We have investigated the inhibition of two-photon absorption in photonic crystals doped with an ensemble of four-level nanoparticles. The particles are interacting with one another by the dipole–dipole interaction. Dipoles in nanoparticles are induced by a selected transition. Numerical simulations have been performed for an isotropic photonic crystal. Interesting phenomena have been predicted such as the inhibition of the two-photon absorption due to the dipole–dipole interaction. It has also been found that the inhibition effect can be switched on and off by tuning a decay resonance energy within the energy band of the crystal. A theory of dressed states has been used to explain the results.

Investigation of optical band gap in potassium acid phthalate single crystal

AbstractOptical absorption in photonic crystals of potassium acid phthalate has been measured at room temperature, from which the band gap has been determined and the optical band gap was calculated by using absorption spectrum. The analysis of absorption coefficient in the absorption region reveals a direct band gap of 3.70 eV. Further this study includes the theoretical calculations to determine the optical constant of the material and a technique for photonic band gap tuning which is minimally required to develop the optoelectronic device. It was confirmed that potassium acid phthalate crystal has maximum transparency in the entire visible region and hence it exhibits industrial application oriented properties. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Microwave Absorption in Photonic Crystals Composed of SiC/Resin with a Diamond Structure

Three‐dimensional photonic crystals were fabricated by infiltrating an epoxy mold with a SiC/polyester mixture. The epoxy molds with normal or inverse diamond structures were formed by stereolithography. The size of the mold was 45 mm × 18 mm × 18mm, and the lattice constant of the photonic crystals was 18 mm. The effects of the epoxy mold type, aspect ratio (the ratio of height and diameter of a diamond lattice rod), and number of sample units on the formation of photonic band gap (PBG) and microwave absorption ability along the 〈100〉 direction were studied. The attenuations of microwave transmission and reflection were measured through the photonic crystal samples at a frequency range of 3–12 GHz with a network analyzer. The results obtained suggest that the combination of the absorbing material SiC and diamond structure has a dual effect to form a PBG with a high absorption ability.

Influence of eigenmode characteristics on optical tuning of a two-dimensional silicon photonic crystal

Ultrafast pump-probe measurements on a two-dimensional (2-D) silicon photonic crystal are used to show the influence of a pump eigenmode's spatial characteristics on the crystal's optical tuning properties. Electron-hole pairs are generated by two-photon absorption of $130\phantom{\rule{0.3em}{0ex}}\mathrm{fs}$, $1.5\phantom{\rule{0.3em}{0ex}}\ensuremath{\mu}\mathrm{m}$ pulses via different crystal eigenmodes and spatially modify the crystal's refractive index via Drude effects; characteristics of an eigenmode near $1.9\phantom{\rule{0.3em}{0ex}}\ensuremath{\mu}\mathrm{m}$ are monitored via time-resolved reflectivity. For a pump eigenmode producing an inhomogeneous carrier distribution, diffusion is responsible for an initially fast ($10\phantom{\rule{0.3em}{0ex}}\mathrm{ps}$ time scale) component of the recovery of the probe reflectivity with surface recombination accounting for a slower response ($700\phantom{\rule{0.3em}{0ex}}\mathrm{ps}$ time scale) after the carriers are nearly uniformly distributed within the silicon backbone. When carriers are initially generated homogeneously in the silicon, surface recombination alone controls the time evolution of the probed mode. A simple expression is developed for the mode-dependent two photon absorption in photonic crystals and a simple perturbation technique is used to treat modifications to photonic crystal eigenmodes by small refractive index changes.

Semiconductor absorption in photonic crystals

Absorption spectra of semiconductor structures in photonic crystal environments are investigated numerically. It is shown that the periodic dielectric structuring changes the local optical and Coulomb interaction properties of semiconductor electron–hole excitations. The structurally induced modifications offer the possibility to design important aspects of the optoelectronic semiconductor properties.