Wavelength-tunable diffraction spectrum influenced by surface plasmons of an echelon-like grating
劉同凱1, 曹永昌1, 蔡明善1*
1Department of Electrophysics, National Chiayi University, Chiayi, Taiwan
* presenting author:Ming-shan Tsai, email:mstsai@mail.ncyu.edu.tw
An echelon-like grating with tunable diffraction spectrum was demonstrated. The grating composed of nanoparticles with thickness gradient increased in grating vector direction was fabricated by photo-lithography, wedge-shaped coating of gold film, and annealing process. Because of the localized surface plasmon resonance strongly depended on the size parameter, the spectrum of the first order diffraction would be effectively modulated by beam size and probe position of the incident light. The wavelength difference Δλ of the spectrum peaks for the two first order diffraction was increased with the extended beam size. Δλ was declined as probe beam moved toward the larger size of nanoparticles. This is because absorption spectrum of nanoparticles had a broader full width at half maximum.

Keywords: surface plasmon, nanoparticles, echelon grating, diffraction