High quality ZnO microtubes with hexagonal cross sections, fabricated via an oxidation-sublimation process, are studied as novel optical resonators. Whispering gallery modes, Fabry-P erot modes, and an additional set of modes with different polarizations are directly observed in the visible spectral range at room temperature by using the spatially resolved spectroscopic technique. The diameter and wall thickness of the microtube are crucial for light modulation. The experimental results are explained and fitted with a plane wave interference model and Cauchy dispersion formula for refractive indices.

Phonon properties of boron nitride nanotubes (BNNTs) were investigated using Raman spectroscopy at different temperatures and new sp3-bonded BN vibrations were identified. The Raman peak of the mode of BNNTs is found to be downshifted and broadened compared to that of hexagonal BN at the same temperature. By increasing the temperature, the energy of the mode and the sp3-bonding mode are downshifted, with the temperature coefficients being −0.010 and −0.069 cm−1/K, respectively. We attribute this downshifting to anharmonic effects as well as the elongation of the B–N bond in BNNT structures with increasing temperature.

The In2O3 nanowires with hexagonal cross section as optical whispering gallery resonators were fabricated by using a simple in situ thermal oxidation method. Whispering gallery modes (WGMs) with different polarizations in the visible spectral range were observed at room temperature. The experimental observations were well described by the plane wave model and Cauchy dispersion formula (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

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