Design of Infrared SPR Sensor Based on Bimetallic Nanowire Gratings on Plastic Optical Fiber Surface

In this paper, a bilayer metallic grating with pitch of
$1~\mu $
m on the flank of a cylindrical plastic optical fiber was proposed as a novel optical sensor. Surface plasmon resonance excited by this structure for refractive index sensing is investigated by finite difference time domain methods. A theoretical sensitivity of 643.75 nm/RIU is obtained, where the wavelength of the resonant sharp dip is obviously shifted from 1.398
$\mu $
m to 1.501
$\mu $
m for surrounding refractive index increased from 1.33 to 1.49. Several factors which affect the accuracy of the device, such as the polarization state of the incident light, grating pitch, and refractive index of the sensing medium, are discussed. The successful fabrication of the grating indicates the feasibility of the devices. The sensor is expected to have potential applications in the chemical, biomedical, environmental safety, and food safety industries as well as in many other aspects.