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 µm², 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.