Monolithically‐Integrated Silicon Photonic Spectrometer with a High‐Q Single‐Microring

Abstract Highly‐integrated spectrometers with performance excellence are extremely desired for various applications, such as consumer electronics and human health wellness. Here, a monolithically‐integrated single‐microring spectrometer is proposed and realized. An innovative scheme of utilizing the free spectral range (FSR) dispersion for a single‐microring and strategically inducing resonant peaks red‐shift more than twice of the FSR is proposed. In this way, the working window of the single‐microring is significantly extended far beyond the FSR limitation with the assistance of reconstruction algorithm. Moreover, the single‐microring is realized with a high‐ Q factor by introducing low‐loss broadened optical waveguides designed with modified‐Euler curves, resulting in high‐resolution spectrum measurement. The monolithically‐integrated silicon single‐microring spectrometer with a Ge/Si photodetector, is experimentally demonstrated with a resolution as high as 0.02 nm in a broad working window of 66 nm (which is >15 times larger than the microring's FSR). Besides, the present on‐chip spectrometer is fabricated with standard processes for silicon photonics, showing an ultra‐compact footprint of 370 × 110 µm 2 , which is one of the smallest monolithically‐integrated spectrometer to date. The present spectrometer is expected to be very attractive for realizing low‐cost portable sensing modules and lab‐on‐a‐chip systems because of the performance excellence, the footprint compactness and the integration density.