On-Chip Notch Filter on a Silicon Nitride Ring Resonator for Brillouin Spectroscopy

Noncontact Brillouin spectroscopy is a purely optical and label-free method to retrieve fundamental material viscoelastic properties. Recently, the extension three-dimensional imaging modality has paved way novel exciting opportunities in biomedical field, yet detection of spectrum remains challenging as consequence dominant elastic background light that typically overwhelms inelastic peaks. In this Letter, we demonstrate fully integrated ultra-compact notch filter based on an ring resonator fabricated silicon nitride platform. Our on-chip was measured have 10 dB extinction ratio Q factor 1.9x10^5. The experimental results provide proof-of-concept ability attenuate light, heralding future developments integrated, low-cost spectrometers.