The fabrication, fluorescence dynamics, and whispering gallery modes of aluminosilicate microtube resonators

In this paper a novel technique for the production of aluminosilicate microtubes, which are shown to act as optical cylindrical microresonators, is described. The free-standing microbes are fabricated by using vacuum-assisted wetting and filtration of silica gel through a microchannel glass matrix. The microtubes are studied using scanning electron microscopy, micro-photoluminescence spectroscopy, and fluorescence lifetime imaging confocal microscopy. In the emission spectra of the microresonators 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 sow a large evanescent filed extending many micrometers beyond the tube radius. Applications for these novel microresonators will be in the areas of microlasers and microsensors and quantum information processing.