Compact MEMS-Based Computational Mid-Infrared Spectrometer on Silicon-on-Insulator Platform

Microspectrometers have been rapidly developed in the past few years due to their advantages of compact footprint, low cost, and in-situ measurement capability. The mid-infrared (MIR) has received great attention as a key band in spectroscopic sensing. However, the development of compact and high-performance MIR microspectrometer is still in its infancy. Here, we present a MEMS-based on-chip computational MIR microspectrometer that uses an in-plane comb-drive actuator to modulate a directional coupler built on the most common silicon-on-insulator platform. The in-plane comb-drive actuator can break through the limitation of photolithography resolution to reduce the waveguide coupling spacing, enhance the coupling strength, and increase the optical path difference, thereby improving the resolution and the compactness of the spectrometer. A spectral resolution of 3 nm and a bandwidth of 300 nm ($4-4.3 \mu \text{m})$ are achieved within a compact footprint of100 $\times 1000\mu \text{m}^{2}$.