Regenerative pulsation in silica microspheres.

Regenerative pulsation from whispering gallery modes excited by a continuous-wave laser beam is observed in silica microspheres that feature a diminishing thermal nonlinearity near 20 K. The regenerative pulsation arises from the competition between Kerr nonlinearity and the much reduced thermal nonlinearity, when the two nonlinearities with very different timescales are comparable in magnitude but opposite in sign.