title: Tuning response range of a transmission-based fiber-optic refractometer through LP₁₁ mode.
abstract: A kind of sensing scheme is theoretically proposed to efficiently tune the response range of a fiber-optic refractometer based on the adiabatic transmission of the higher-order LP11 mode. Near the cut-off condition, transmission of the LP11 mode is a strong function of the refractive index (RI) under detection; thus high sensitivity is achieved. The cut-off RI value is dependent on the waist diameter; therefore the response RI range with high sensitivity can be changed just by altering the waist diameter. Theoretical calculations reveal that the response range is effectively tuned from 1.43-1.438 to 1.35-1.365 when the waist diameter is reduced from 2.5 to 1 μm. The proposed fiber-optic sensor is also superior when used as an absorbing sensor since the higher-order mode LP11 has a much larger power fraction in the evanescent field compared with the fundamental mode LP01 of the same fiber.
authors.forename: Guigen
authors.initials: G
authors.lastname: Liu
authors.forename: Kaiwei
authors.initials: K
authors.lastname: Li
authors.forename: Fang
authors.initials: F
authors.lastname: Dai
authors.forename: Peng
authors.initials: P
authors.lastname: Hao
authors.forename: Wenchao
authors.initials: W
authors.lastname: Zhou
authors.forename: Yihui
authors.initials: Y
authors.lastname: Wu
authors.forename: Ming
authors.initials: M
authors.lastname: Xuan