Ultra-compact on-chip spectrometer based on thermally tuned topological miniaturized bound states in the continuum cavity

On-chip spectrometers are key components in many spectral sensing applications owing to their unique advantages in size and in situ detection. In this work, we propose and demonstrate a class of thermally tunable spectrometers by utilizing topological miniaturized bound states in the continuum (mini-BIC) cavities in a photonic crystal (PhC) slab combined with a metal micro-ring heater. We achieve a resolution of 0.19 nm in a spectral range of ∼6 nm, while the device’s footprint is only 42×42 μ m 2 . The mini-BIC spectrometer works in nearly vertical incidence and is compatible with array operation. Our work sheds light on the new possibilities of high-performance on-chip spectrometers for applications ranging from bio-sensing to medicine.