Simultaneous measurement of temperature and refractive index using focused ion beam milled Fabry-Perot cavities in optical fiber micro-tips

Abstract

Optical fiber micro-tips are promising devices for sensing applications in small volume and difficult to access locations, such as biological and biomedical settings. The tapered fiber tips are prepared by dynamic chemical etching, reducing the size from 125 mu m to just a few mu m. Focused ion beam milling is then used to create cavity structures on the tapered fiber tips. Two different Fabry-Perot micro-cavities have been prepared and characterized: a solid silica cavity created by milling two thin slots and a gap cavity. A third multi-cavity structure is fabricated by combining the concepts of solid silica cavity and gap cavity. This micro-tip structure is analyzed using a fast Fourier transform method to demultiplex the signals of each cavity. Simultaneous measurement of temperature and external refractive index is then demonstrated, presenting sensitivities of 15.8 pm/K and -1316 nm/RIU, respectively. (C) 2016 Optical Society of America