Simulation of an In-Line Optofluidic Refractive Index Sensor Based on a Seven-Liquid-Core Teflon-Cladding Fiber

We have proposed and theoretically demonstrated a highly sensitive optofluidic refractive index (RI) sensor based on a modal interferometer formed by a section of liquid-filled seven-hole Teflon-cladding fiber sandwiched by two standard single mode fibers (SMFs). When liquid gets into the air hole voids of the seven-hole Teflon-cladding fiber, it forms a seven-liquid-core fiber (SLCF) and the light waves are well guided by the liquid cores because of total inner reflection. When the input SMF is aligned to the central core of the SLCF, only two pairs of supermodes with different effective indices will be excited, and thus a Mach-Zehnder modal interferometer is constructed. The spectral response of the modal interferometer to the variation of RI of the liquid cores is numerically simulated through finite-element method software. The dependence of the RI sensitivity on the size and center distance of air holes of the SLCF are studied, respectively. Finally, a very high sensitivity of 24,577 nm/RIU for RI in the vicinity of 1.333 is achieved. The proposed sensor is potentially useful for label-free biochemical sensing due to its high sensitivity and very little sample consumption.