Evanescently coupled multimode spiral spectrometer

TL;DR

This paper introduces a compact high-resolution spectrometer using evanescently-coupled multimode spiral waveguides, achieving 0.01 nm resolution and simultaneous recovery of multiple spectral channels with enhanced bandwidth.

Contribution

The work presents a novel spiral spectrometer design leveraging evanescent coupling for improved spectral resolution and multiplexing capabilities.

Findings

Achieved 0.01 nm spectral resolution at 1520 nm

Simultaneous recovery of 40 spectral channels

Enhanced bandwidth via compressive sensing

Abstract

We designed a high-resolution compact spectrometer based on an evanescently-coupled multimode spiral waveguide. Interference between the modes in the waveguide forms a wavelength-dependent speckle pattern which is used as a fingerprint to identify the input wavelength after calibration. Evanescent coupling between neighboring arms of the spiral results in a non-resonant broad-band enhancement of the spectral resolution. Experimentally, we demonstrated a resolution of 0.01 nm at a wavelength of 1520 nm using a 250 {\mu}m radius spiral structure. Spectra containing 40 independent spectral channels are recovered simultaneously and the operation bandwidth is significantly increased by applying compressive sensing to sparse spectra reconstruction.