In this paper we describe a novel technique for the fabrication of aluminosilicate microfibres and microtubes which are
shown to act as optical cylindrical microresonators. The alumosilicate microfibres and microtubes were fabricated by
using vacuum-assisted wetting and filtration of silica gel through a microchannel glass matrix. The microfibres and
microtubes were studied using Scanning Electron Microscopy (SEM), micro-photoluminescence spectroscopy and
fluorescence lifetime imaging confocal microscopy. In the emission spectra of the micro-resonators we find very narrow
periodic peaks corresponding to the whispering gallery modes of two orthogonal polarizations with quality factors up to
3200. A strong enhancement in photoluminescence decay rates at high excitation power demonstrates the occurrence of
amplified spontaneous emission from a single microtube. These microtubes show a large evanescent field extending
many microns beyond the tube radius. Potential applications for these novel microresonators will be in the area of optical
microsensors for a single molecule detection of biological and chemical species, including anti-terrorism and defense
We present a detailed study of the photonic modes in microtube cavity of ~ 7-8 μm outer diameter that can act as micron-scale optical cylindrical resonator. We demonstrate a new route to the fabrication of individual microtubes with the maximum length of 200 &mgr;m, using a vacuum assisted wetting and filtration through a microchannel glass matrix. The microtubes were studied using micro-photoluminescence spectroscopy and luminescence lifetime imaging confocal microscopy. In the emission spectra of the microresonators we find periodic very narrow peaks corresponding to the whispering gallery modes of two orthogonal polarizations with quality factors upto 3200 at room temperature. In order to identify the peaks in the observed mode structure, we have adopted the boundary-value solution to the problem of scattering of electromagnetic waves by a dielectric micro-cylinder. A strong enhancement in photoluminescence decay rates at high excitation power suggest the occurrence of amplified spontaneous emission from a single microtube. The evanescent field in these photonic structures extends a couple of micrometers into the surroundings providing the possibility for efficient coupling to an external photonic device.
Porous materials in general have received great attention from the last century. The development of new porous materials and the preparation of new composites based on porous materials is a subject of interest. The development of porous silicon based optical composite materials opened up new ways of incorporating optically active sol-gel materials into porous silicon. High purity silica optical fibres allow the most rapid and efficient data transmission. The objective of this work is to develop micro-channel glass / porous silicon-rare earth doped xerogel and glass composites, which would serve as compact optical amplifiers and delay line devices. Micro-channel glass / porous silicon-xerogel composites have been prepared by incorporation of sol-gel prepared from tetraethoxysilane, aluminium iso-propoxide and europium chloride into the porous matrix. Both xerogel and glass composites have been studied by various techniques such as FTIR, micro-Raman, photoluminescence spectroscopy, EDX and Scanning Electron Microscopy (SEM).