Waveguide lasing from V-shaped ZnO microstructure.

A V-shaped optical resonance cavity was obtained from ZnO microstructures grown by thermal chemical vapor deposition. Strong laser emissions were observed in three regions--the tip of the two branches and the bottom facet of the V-shaped microstructures--under UV laser excitation at room temperature. In the region where the diameter of the branches was smaller than the wavelength of the laser light, light could not propagate into the tip due to the cutoff phenomenon, resulting in partial reflection.

Optical resonant cavity in a nanotaper.

The present study describes an optical resonant cavity in a nanotaper with scale reduction from micro to several nanometers. Both experimental results and a finite-difference time-domain (FDTD)-based simulation suggested that the nanometer-scale taper with a diameter similar to the wavelength of light acted as a mirror, which facilitated the formation of a laser cavity and caused lasing in ZnO nanotapers. As the light inside the nanotaper propagated toward the apex, the lateral mode was reduced and reflection occurred.