Counterpropagating Whispering-Gallery-Modes of Rolled-up Semiconductor Microtubes

We report on the first experimental demonstration of counterpropagating whispering-gallery-modes (WGMs) of rolled-up semiconductor microtubes. We studied the thermo-optic effect of the microtube and achieved optical-optical modulation in both propagating and counterpropagating WGMs. We also realized a thermal wavelength-switchable fiber ring laser using the counterpropagating WGMs of the microtube.