Optofluidic conical microresonator for precise displacement sensing

Abstract

In the present work we report fabrication of a compact optical displacement sensor based on whispering gallery mode with common materials on Polydimethylsiloxane (PDMS) medium with mold master technique. Conical and hollow geometry of microcavity filled with Rhodamine B-doped Glycerol as active medium. The fabricated device can be utilized for sensing applications. Coupling junction can be tuned so that moving the conical microcavity of about 100 μm in the axial direction is equivalent to ∼1.5 nm shift in resonant wavelength. Also, a small change in concentration of active medium results in a shift in the resonant wavelength which provides the feasibility of sensing the refractive index. The proposed structure demonstrates the ability of considerably high-resolution sensing for fine displacement steps which is limited by the resolution of the spectrometer (0.6 nm).