A.V. Fokin

Eu3+ emission in an anisotropic photonic band gap environment

Eu3+ ions have been incorporated into the silica skeleton of synthetic opal. The effect of the anisotropic photonic band gap structure upon the emission characteristics has been studied in the case where the emission bandwidth is narrower than the stop-band. Either suppression or enhancement of the spontaneous emission at the wavelength of the radiative transition has been observed, depending on the relative position of the emission band and the stop-band.

ANISOTROPIC PHOTOLUMINESCENCE IN INCOMPLETE THREE-DIMENSIONAL PHOTONIC BAND-GAP ENVIRONMENTS

The effect of an incomplete three-dimensional photonic band-gap structure upon the wideband photoluminescence from bare opal and opal impregnated with ZnS has been studied by means of angular-resolved photoluminescence. It has been shown that the photoluminescence becomes anisotropic in accordance with the angular dispersion of the stop band. Suppression of the spontaneous emission in the stop-band energy region and amplification of the spontaneous emission at the edge of the stop band have both been demonstrated.

Enhancement of the photonic gap of opal-based three-dimensional gratings

The “semimetallic” photonic band gap formed in a synthetic opal has been increased by depositing a layer (InP or TiO2) with high refractive index on the inner surface of opal voids. Reflectance spectra of the composites (nanolayers assembled within grating voids) are correlated with both the photonic structure of the opal and electronic structure of the semiconductor.

Optical properties of ordered three-dimensional arrays of structurally confined semiconductors

Three-dimensional arrays of nanometer size clusters have been realised using an opal matrix by filling its voids with CdS and CdSe. From the absorption edge and the luminescence behaviour it is concluded that the average size of the clusters is about 10 nm and that the energy is relaxed via semiconductor nanocluster states and via defect levels in the opal, depending on the strength of the nanocluster-matrix interaction. It is suggested that this class of materials is conducive to the realisation of photonic bandgap structures for visible light and preliminary emission results in opal filled with CdSe support this possibility.

Stop-band structure in complementary three-dimensional opal-based photonic crystals

The stop-band width and angular dispersion have been traced by angle-resolved reflectance spectroscopy for two opposite configurations of opal-based photonic crystals where either the silica balls possess a higher refractive index than the voids or vice versa. It has been demonstrated that filling the empty voids of opal with a material of higher refractive index than silica results in widening of the stop-band and squeezing of its dispersion, thus improving the stop-band of the opal grating towards the omnidirectional photonic band-gap situation.

Photon Localisation in Ordered Packages of Granular Semiconductors

The anisotropic photonic crystals have been prepared by impregnating the interstitial voids of synthetic opals with CdS and ZnS. The interplay of coherent and incoherent scattering has been traced by reflectance and photoluminescence (PL) spectroscopy. The reduction of anisotropy of the photonic bandgap (PBG) structure with increasing loading has been observed, as compared with bare opal. The interplay between the photonic and electronic energy structures of the composite material results in an amplified spontaneous emission (ASE).

Thin-film coated opals-an approach to 3-dimensional photonic crystals

Summary form only given. Synthetic opal provides a 3D template for the formation of photonic crystals for visible light operation. Improvement of the photonic bandgap structure of opal has been approached via coating the inner surface of the opal with TiO/sub 2/, InP or GaP layers using CVD and MOCVD. In contrast to other methods of embedding high refractive index materials in opal these methods allow the crystallinity of the original template to be preserved. The high refractive index coating serves to increase the width of the photonic stop-band and to squeeze the angular dispersion of the stop-band.