Nonlinear Effects due to Thermo-Optical Instability in Microsphere Resonators

Microresonators of different geometries appeared to be promising part for future generations of integrated optical circuits. Due to extremely low losses (high resonator Q-factors and ultra small resonance bandwidths, respectively) the microresonators possess high level of energy concentration and, in turn, unprecedented low level of threshold for various nonlinear effects. In this work, detailed investigation of thermo-optical effects in microspheres made on optical fiber end is presented. Quasi "broadening" of the resonance coupling peaks and their shifting have been observed in the tests of light coupling into the high-Q microspherical resonators through the optical tapered fiber. The both effects have been explained by thermo-optical nonlinearity causing resonance bistability.