Highly sensitive self-referenced surface plasmon resonance fiber optic sensor with indium tin oxide/metal/dielectric structure

A highly sensitive self-referenced surface plasmon resonance (SPR) fiber optic sensor with an indium tin oxide (ITO)/metal/dielectric structure is proposed and theoretically analyzed using the transfer matrix method-based numerical simulations. First, the thicknesses of the metal and ITO films are optimized to realize self-referenced sensing with low normalized transmission power at the resonance peak. Then, a thickness-optimized dielectric (TiO2) film is employed on top of the metal film to improve the sensitivity of the proposed self-referenced sensor. In addition, a comparison between the traditional self-referenced sensor and the proposed self-referenced sensor with the dielectric film are carried out. The self-referenced sensor with a 36 nm ITO/37 nm Ag/70 nm TiO2 structure obtains up to 14510 nm/RIU in sensing sensitivity when the refractive index of the analyte varies from 1.33 to 1.37, which is improved by 421% compared with the traditional one without the dielectric. At the same time, the shift of the self-referenced resonance wavelength changes little for the proposed structure. The proposed ITO/metal/dielectric structure-based fiber optic sensor exhibits highly sensitively self-referenced sensing performance in the near infrared band, which can promote its application in the field of biosensors.