Fabrication of plasmonic surface relief gratings for the application of band-pass filter in UV-Visible spectral range

TL;DR

This paper reports the fabrication and characterization of plasmonic surface relief gratings on silver halide films for UV-Visible band-pass filtering, demonstrating their optical properties and potential for optical device applications.

Contribution

It introduces a simple method to fabricate plasmonic gratings with controlled periods using conventional SEM on silver halide films for optical filtering applications.

Findings

Maximum diffraction efficiency of 4% at 10 μm period

Bandwidth of 400 nm for 10 μm period grating

LSPR dip at ~366 nm linked to embedded silver nanoparticles

Abstract

The measured experimental results of optical diffraction of 10, 5 and 3.4 micrometer period plasmonic surface relief grating are presented for the application of band-pass filter in visible spectral range. Conventional scanning electron microscopic (SEM) is used to fabricate the grating structures on the silver halide based film (substrate) by exposing the electron beam in raster scan fashion. Morphological characterization of the gratings is performed by atomic force microscopy (AFM) shows that the period, height and profile depends on the line per frame, beam spot, single line dwell time, beam current, and accelerating voltage of the electron beam. Optical transmission spectra of 10 micrometer period grating shows a well-defined localized surface plasmon resonance (LSPR) dip at ~366 nm wavelength corresponding to gelatin embedded silver nanoparticles of the grating structure. As the period of the grating reduces LSPR dip becomes prominent. The maximum first order diffraction efficiency (DE) and bandwidth for 10 micrometer period grating are observed as 4% and 400 nm in 350 nm to 800 nm wavelength range respectively. The DE and bandwidth are reduced up to 0.03% and 100 nm for 3.4 micrometer period grating. The profile of DE is significantly flat within the diffraction bandwidth for each of the gratings. An assessment of the particular role of LSPR absorption and varied grating period in the development of the profile of first order DE v/s wavelength are studied. Fabrication of such nano-scale structures in a large area using conventional SEM and silver halide based films may provide the simple and efficient technique for various optical devices applications.