Scalable Miniature On-chip Fourier Transform Spectrometer For Raman Spectroscopy

TL;DR

This paper introduces a compact, multi-aperture waveguide-based Fourier Transform Spectrometer on a chip that enhances Raman spectroscopy capabilities for applications like biomedical diagnostics and material sensing.

Contribution

The work presents a scalable, miniaturized on-chip FTS with multi-aperture design, enabling high-throughput Raman spectroscopy in a small footprint, which was previously limited by conventional spectrometer sizes.

Findings

Achieved a spectral range of 40 nm and resolution of 0.5 nm.

Successfully demonstrated Raman spectroscopy of various chemicals.

LASSO regression improves spectrum reconstruction accuracy.

Abstract

Miniaturized spectrometers for Raman spectroscopy have the potential to open up a new chapter in sensing. Raman spectroscopy is essential for material characterization and biomedical diagnostics, however, its weak signal and the need for sub-nanometer resolution pose challenges. Conventional spectrometers, with footprints proportional to optical throughput and resolution, are difficult to integrate into compact devices such as wearables. Waveguide-based Fourier Transform Spectrometers (FTS) enable compact spectrometers, and multi-aperture designs can achieve high throughput for applications such as Raman spectroscopy, however, experimental research in this domain remains limited. In this work, we present a multi-aperture SiN waveguide-based FTS overcoming these limitations and enabling Raman spectroscopy of isopropyl alcohol, glucose, Paracetamol, and Ibuprofen with enhanced throughput. Our spectrometer chip, fabricated on a 200 mm SiN wafer, with 160 edge-coupled waveguide apertures connected to an array of ultra-compact interferometers and a small footprint of just 1.6 mm x 4.8 mm, achieves a spectral range of 40 nm and a resolution of 0.5 nm. Experimental results demonstrate that least absolute shrinkage and selection operator (LASSO) regression significantly enhances Raman spectrum reconstruction. Our work on waveguide-based spectrometry paves the way for integrating accurate and compact Raman sensors into consumer electronics and space exploration instruments.