Foundry-based waveguide-enhanced Raman spectroscopy in the visible

Abstract

Waveguide-enhanced Raman spectroscopy (WERS) is an analytical technique frequently employed for chemical and biological sensing. Operation at visible wavelengths to harness the inverse fourth power with excitation wavelength signal scaling of Raman scattering intensity is desirable, to combat the inherent inefficiency of Raman spectroscopy. Until now, WERS demonstrations in the visible have required custom materials and fabrication, resulting in high losses and low yields. In this work, we demonstrate a silicon nitride (SIN) visible WERS platform fabricated in a 300 mm complementary metal-oxide semiconductor (CMOS) foundry. We measure the propagation loss, coupling loss, WERS signal, and background for WERS spirals designed for 532 nm and 633 nm pump wavelengths. We compare these results to the state-of-the-art near-infrared WERS platform at 785 nm. Further, we theoretically validate the relative performance of each of these WERS configurations, and we discuss the optimal WERS configuration at visible wavelengths. We conclude that a configuration optimized for 785 nm pumping provides the greatest signal-to-background ratio in the fingerprint region of the spectrum, and pumping at 633 nm maximizes Stokes signal out to 3000 cm−1.