Adjusting diffraction spectrum of an echelon-like grating influenced by surface plasmon of nanomaterials

This article aims to study the varying diffraction spectrum phenomenon influenced by surface plasmon of nanomaterials. Experiments used silver nanoparticles to build the echelon-like grating as test samples, where the grating spacing of line pattern is 10 μm and within the width of silver nanoparticles line is 5 μm alternately. In this work, the silver stripes with gradient thickness were first formed line pattern alternately with glancing angle deposition and photolithography, and then annealed at temperature of 250 °C for 3 mins to fabricate the silver nanoparticles as bowl-like forms. Thicknesses of the silver nanoparticles in the echelon-like grating increase from 0 nm to 40 nm and their diameters grow from 0 nm to 35 nm with quasilinear increment simultaneously. Analyzing the varying diffraction spectrum was focused on observing the first order diffraction by changing the beam size and the probe position of the incident light. The significant results show that the bigger the incident light beam size, the larger the peak wavelength difference (Δλ) of the two first order diffractions. Moreover, the peak spectrum is shifted to long wavelength and Δλ is diminished by probing area with big size of nanoparticles.