This paper describes a silicon microresonator with which a new class of fiberoptic sensors can be formed. The basic principle is that the measured value changs the resonance frequency of the microresonater.The flexural vibrations of the microresonator are excited photothermally under the action of modulated optical radiation. The fabrication of microbridge-type resonators made of single-crystal silicon is presented. The mechanism by which microresonators are optically activated is identified and discussed.