Efficient Frequency Upconversion Photodetection in Heterojunction of InSe and Silicon Photonic Crystal Cavity

Frequency upconversion photodetection by two-dimensional (2D) materials with nonlinear optical response is an appealing technique for applications such as extending photodetection wavelength range, autocorrelation measurement, and high-efficiency single photon detection. However, the frequency upconversion efficiency in 2D materials is limited due to the low efficiency of nonlinear optical processes and atomic light-matter interaction length. Here, the efficient frequency upconversion photodetection is realized by van der Waals (vdW) integration of a few-layer InSe with a silicon photonic crystal cavity (Si-PPC). With the large second-order nonlinearity of InSe and enhanced light-matter interaction by Si-PCC, continuous wave (CW) pumped second harmonic generation (SHG) is demonstrated with pump power down to 100 µW. Further, InSe and Si absorb the SHG photons and generate photocarriers which are separated and collected by the n-InSe/p-Si heterojunction. A frequency upconversion photoresponsivity of 16 µA W⁻¹ with a CW laser at 1467 nm is obtained. More efficient SHG with pulsed laser improves the responsivity to 3.9 mA W⁻¹ with quadratic power dependence, which is record-high among the frequency upconversion photodetectors based on 2D materials. This work opens up opportunities for a high-efficiency 2D material nonlinear photodetector integrated on photonic integrated circuits.