Silicon-on-insulator wavelength-selective filter with integrated detectors at the 2 µm wave band

The short-wave infrared range is highly significant for spectroscopic sensing and upcoming optical communication applications. Integrating active and passive photonic components is essential to achieve compact optical solutions. In this paper, we show, for the first time to our knowledge, a wavelength-selective detection system based on the heterogeneous integration of two grating-coupled InGaAs photodetectors operating at the 2µm wave band, with a wavelength selectivity provided by a dual-channel Mach-Zehnder interferometer fabricated using a silicon-on-insulator (SOI) wafer. A full system responsivity of 0.1 A/W is measured together with >9.5 dB rejection ratio at two wavelengths. To our knowledge, we achieve the lowest measured dark current density (7.6 × 10^-4 A/cm² at -2 V) with micro-transfer printed integrated detectors.