Facile method of infilling photonic silica templates with rare earth element oxide phosphor precursors
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A method for preparing rare-earth element-doped yttrium oxide phosphor photonic band gap crystals (PBG) is described, which obviates the necessity for multiple infilling of the opal-like template. The method utilizes (i) the re-dissolving and the concentration of previously precipitated spherical phosphor particles made by homogeneous precipitation methods into a viscous precursor phosphor solution, and (ii) formation of an opal-like template of polystyrene or silica spheres. A procedure is outlined that permits the precursor solution to be drawn into the template in a controlled manner that can be easily monitored using an optical microscope. Attenuation of the strong, red cathodoluminescent emission is observed in Y2O3:Eu3+ phosphor PBG crystals that are engineered to have a stopband overlapping the emission bands in the red region. This attenuation results from Bragg diffraction of the light emitted within the PBG phosphor crystals.
I. INTRODUCTION
Photonic crystals are materials with a periodic refractive index modulation. These crystals inhibit electromagnetic wave propagation for a particular wavelength range, opening up a photonic band gap (PBG).1,2 The ultimate aim is to produce these materials with a significant extended three-dimensional substructure with periodic nanoscale lattice parameters with dimensions comparable to optical wavelengths. Applications of these materials have centered on the exploitation and manipulation of their light propagation and spontaneous emission properties.1–5 If large three-dimensional PBG crystals can be fabricated commercially at optical wavelengths (this infers that the synthesis would need to be relatively simple and cost effective), new photonic devices such as tight angle optical fibers, photonic transistors, and PBG phosphor materials should be attainable in the near future.6–10 A new technology would be born in which photonic integrated circuits would open up the possibility of a photonic computer.11,12 Colloids of polystyrene (PS) or silica spheres (SS) have been found to be ideal to form self-assembled blocks of synthetic bare opal-like template.13–17 The bare opal-like template can then be infilled within the air spaces between the spheres with a material of medium to high refractive index such as we have previously Address all correspondence to these authors. a) e-mail: [email protected] b) e-mail: [email protected] DOI: 10.1557/JMR.2004.0212 1656
http://journals.cambridge.org
J. Mater. Res., Vol. 19, No. 6, Jun 2004 Downloaded: 10 Mar 2015
reported.6–10 The spheres of the resulting infilled opallike template can then be eliminated producing an inverse opal PBG crystal with high refractive index contrast.17–20 A number of problems have been encountered by all researchers in the pursuit of these exotic opal-like materials; these include small crystal size, cracking of the template, defects, faulting, fragility of the bare template (in particular PS), break up of the template during infilling, and general damage during processing.21–23 There are two signif
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