Full-fiber-type sensing system for physical quantities using a photothermally vibrated quartz-core cantilever

A quartz-core cantilever fabricated from an optical fiber tip is proposed as a practical sensor for measurement of various physical quantities. Its operation is based on the principle that the resonance characteristics of the photothermally vibrated cantilever vary with the surrounding physical quantities. The cantilever is studied as a mechanical sensor for monitoring film thickness, liquid density and viscosity using a excitation vibration and detection system constructed solely of optical fiber. Thickness monitoring of Au film is possible with an accuracy of 0.5 nm up to a thickness of 500 nm. By utilizing the cantilever in liquid, the resonance frequency and half-power width dependence on the density and viscosity of the liquid were determined.