Ultrasensitive Chemical Detection Using Integrating Cavity-Enhanced Raman Spectroscopy.

Raman spectroscopy is a powerful analytical technique used for molecular detection, identification, and characterization, but its broader utility has been limited by the intrinsically weak spontaneous Raman scattering intensity. In this work, we demonstrate significant Raman signal enhancement using a novel high-performance integrating cavity constructed with newly developed Lambertian materials exhibiting exceptionally high reflectivity. Cavity ringdown measurements yield a peak average reflectivity of 99.943 ± 0.0004% at 610 nm. Raman measurements of bulk methanol, magnesium sulfate, and glycine demonstrate μmol sensitivity using a compact, fiber-coupled 405 nm diode laser delivering 17 mW of optical power. Additionally, limit-of-detection studies performed using a 532 nm diode-pumped solid-state laser at 150 mW demonstrate nanomole-level sensitivity for two common polycyclic aromatic hydrocarbons─benzo[a]pyrene and pyrene. These findings establish integrating cavity-enhanced Raman spectroscopy as a promising approach for compact, high-sensitivity systems in medical, environmental, industrial, and space-based applications.