A packaged, fiber-coupled waveguide-enhanced Raman spectroscopic sensor

TL;DR

This paper introduces a packaged, fiber-coupled waveguide-enhanced Raman sensor that filters background noise on-chip, enabling reliable, compact, and sensitive chemical detection suitable for practical applications.

Contribution

The authors present a novel packaged WERS chip with integrated background filtering and a rugged flow cell, advancing from free-space coupling to fiber-based, chip-scale Raman sensing.

Findings

Effective background filtering improves signal clarity.

Enhanced signal-to-noise ratio with optimized waveguide geometries.

Demonstrated reliable measurements over extended periods.

Abstract

Waveguide-enhanced Raman spectroscopy (WERS) is a promising technique for sensitive and selective detection of chemicals in a compact chip-scale platform. Coupling light on and off the sensor chip with fibers however presents challenges because of the fluorescence and Raman background generated by the pump light in the fibers; as a result all WERS demonstrations to date have used free-space coupling via lenses. We report a packaged, fiber-bonded WERS chip that filters the background on-chip through collection of the backscattered Raman light. The packaged sensor is integrated in a ruggedized flow cell for reliable measurement over arbitrary time periods. We also derive the figures of merit for WERS sensing with the backscattered Raman signal and compare waveguide geometries with respect to their filtering performance and signal to noise ratio.