Fig. 1: Plasmonic chirped gratings for on-chip spectrometer.
From: Imaging-based intelligent spectrometer on a plasmonic rainbow chip
a Illustration of the plasmonic chirped grating being used as an on-chip spectrometer. b SEM images of the plasmonic grating fabricated on a thin Ag film via focus-ion beam milling. The grating is composed from an assembly of multiple 6-groove units. The period of the units increases from 244 to 764 nm along the length of the chip. This allows for a spatial distribution of plasmon resonances, i.e., a “rainbow trapping” effect. The scale bar for the top image is 50 µm; the scale bars for the bottom two images are both 10 µm. c Schematic of a simple reflection mode microscope system to observe “rainbow trapping” patterns on the plasmonic chip. d Images of the “rainbow” color pattern produced by the chirped grating (top panel) and spatial patterns of the plasmonic resonances for narrowband illumination at several center wavelengths (lower panels). e Spectral lineshapes for the spatial patterns of the corresponding center wavelengths in (d).
