Highly sensitive refractive index sensor based on two cascaded microfiber knots with vernier effect

摘要

A highly sensitive refractive index (RI) sensor based on two cascaded microfiber knots with vernier effect is proposed and demonstrated by theoretical arithmetic. Deriving from high proportional evanescent field of microfiber and sharp spectrum fringes induced by vernier effect, a slight change of ambient RI will cause large variation of effective RI and significant wavelength shift of resonant peaks, indicating high sensitivity and resolution of the proposed compound resonator. Numerical analysis demonstrates a high sensitivity of 10000nm/RIU and a resolution of 5.57 × 10~(-5) RIU at the ambient RI around 1.33 for the fiber diameter of 1μm and cavity radii of R_1 = 500μm, R_2 = 547.62μm.