Broadband and High-Resolution Integrated Spectrometer Based on a Tunable FSR-Free Optical Filter Array

Integrated spectrometers provide the possibility of compact, low-cost portable spectroscopy sensing, which is the critical component of the lab-on-a-chip system. However, using existing on-chip designs is challenging to realize a high-resolution miniature spectrometer over a broad wavelength range. Here, we demonstrate an on-chip time-sampling narrowband filter array spectrometer that enables simultaneous acquisition of high-resolution spectra via optical Fabry–Pérot cavities and a large spectral range with tunable free spectral range free filters. Two spectrometers consisting of five and seven filter cells with a compact footprint are fabricated and experimentally characterized, demonstrating a resolution of <0.43 and <0.51 nm and a spectral range of 73.2 and 102.7 nm, respectively. Unknown broad bandwidth input signal spectra can be successfully retrieved. Integrating more filter cells with thermal isolation trenches can dramatically boost the operational spectral range. Such spectrometers may open up new pathways toward spectral analytical applications.