Theoretical model of a planar integrated refractive index sensor based on surface plasmon-polariton excitation with a long period grating

A theoretical model of a new integrated planar surface plasmon-polariton (SPP) refractive index sensor with a long period grating (LPG) is presented and comprehensively investigated. The main principle of operation of this device is based on high-efficiency energy transfer between a p-polarized guided mode propagating in a waveguide layer of the structure and copropagating SPP supported by a metal layer separated from the waveguide layer by a buffer. The high-efficiency energy transfer is realized by means of a properly designed LPG imprinted in the waveguide and buffer layers. This device is compact and free from any moving parts and can be easily integrated into any planar scheme. Our simulations are based on the coupled-mode theory and done at the well-developed and commercialized telecom wavelengths in the 1500 nm window.