Nano-Displacement Measurement Using an Optical Drop-Shaped Structure

This letter presents a new optical fiber structure with the capability of measuring nano-displacement. This device is composed by a cleaved fiber and a drop-shaped microstructure that is connected to the fiber cladding. This optical structure is responsible for the light beam division and the formation of new optical paths. The operation mode consists of the Vernier effect that allows achieving higher sensitivity than the currently sensors. During the experimental execution, displacement sensitivities of 1.05 ± 0.01 nm/μm, 15.1 ± 0.1 nm/μm, 24.7 ± 0.3 nm/μm and 28.3 ± 0.3 nm/μm, were achieved for the carrier, the fundamental of the envelope, the first harmonic and the second harmonic, respectively. The M-factor of 27 was attained, allowing a minimum resolution of 0.7 nm. In addition to displacement sensing, the proposed optical sensor can be used as a cantilever enabling non-evasive measurements.