title: Tubular optical microcavities of indefinite medium for sensitive liquid refractometers.
abstract: Optical microcavities enable circulated light to intensively interact with a detecting liquid, thus promising high sensitivity in fluidic refractometers. Based on Mie scattering theory, we propose a tubular metamaterial device for liquid sensing, which utilizes anisotropic metamaterials with hyperbolic dispersion called indefinite media (IM). Besides traditional whispering gallery modes (WGMs), such tubular cavities can support surface plasmon polariton (SPP) WGMs, enabling high sensitivity liquid detection. Three configurations of such metamaterial tubes for sensing are discussed: tube-in-liquid, hollow-tube-in-liquid and liquid-in-tube; these are analyzed using numerical formulas and compared with dielectric and metal materials. Compared with traditional dielectric media (DM), the IM tubular cavity exhibits a higher sensitivity (S), which is close to that of a metal tubular cavity. However, compared with metal media, such an IM cavity can achieve higher quality (Q) factors similar to the DM tubular cavity. Therefore, the IM tubular cavity can offer the highest figures of merit (QS) for the sensing performance among the three types of materials. Our results suggest a novel tubular optofluidic device based on metamaterials, which could be useful for liquid refractometers.
authors.affiliation: Department of Materials Science, Fudan University, Shanghai 200433, China. yfm@fudan.edu.cn.
authors.forename: Shiwei
authors.initials: S
authors.lastname: Tang
authors.forename: Yangfu
authors.initials: Y
authors.lastname: Fang
authors.forename: Zhaowei
authors.initials: Z
authors.lastname: Liu
authors.forename: Lei
authors.initials: L
authors.lastname: Zhou
authors.forename: Yongfeng
authors.initials: Y
authors.lastname: Mei
mesh_terms: D046210:Microfluidic Analytical Techniques / Q000295:instrumentation; D055096:Optical Devices; D012031:Refractometry / Q000295:instrumentation