Whispering gallery mode emission from microtube cavity

Optical properties were studied of a novel microtube cavity of similar to 8 mu m diameter prepared by vacuum-assisted filtration of aluminosilicate xerogel using micro-channel glass matrix followed by thermal treatment. Periodic very narrow peaks of the emission spectra corresponding to orthogonally polarized whispering gallery modes were detected. The spectral position of different modes were analyzed using Lorenz-Mie theory. The mode assignment permits calculation of the spectral dependence of cavity Q values associated with observed peaks. Intensity-dependent, time-resolved stimulated emission experiments were performed on the single microtube cavity. The results show a strong decrease in emission lifetime with increasing excitation intensity, consistent with a mechanism of amplified stimulated emission.