基于表面等离子体共振的金属纳米结构传感器具有测量精度高、易集成的特点，已广泛应用于生物、化学、材料、光子学和生命科学等诸多领域。然而由于表面等离子体共振在可见光波段具有较大的辐射损耗，导致等离子体共振传感器谐振峰较宽，极大地限制了传感器的性能。本文采用不对称双椭圆柱结构在等离子体共振传感器中引入不对称性，产生Fano共振以实现窄带光谱特性。通过优化结构参数，在681 nm波长处，得到了半高全宽(FWHM)仅为10.8 nm的谐振谷。该传感器在环境折射率1.0~1.1的变化范围内，折射率灵敏度可以达到299 nm/RiU，品质因数可以达到27.8。该传感器在高折射率灵敏度传感应用方面有着巨大的潜力。

Plasmonic sensor based on metallic nanostructures is a promising platform for applications, such as biology, chemistry, materialogy, photonics and bioscience due to their attractive properties. However, the sensitivity of plasmonic sensors is usually limited by broad-spectral features due to large radiative loss of metallic nanostructures in visible region. in this paper, we introduce structural asymmetry to generate the Fano resonance in the metallic nanostructure composed of asymmetric ellipsoidal pair. The distinct Fano-like resonance around wavelength of 681 nm possesses sharp peak as narrow as 10.8 nm. And the Fano mode exhibits high refractive index sensitivity as large as 299 nm/RiU. Due to the excitation of sharp spectral features, high figure of merit of 27.8 at the Fano resonance is obtained in a wide refractive index range of 1.0~1.1. This device is promising for the applications of high sensitivity microchip sensor.