Giant optical absorption of a PtSe₂-on-silicon waveguide in mid-infrared wavelengths

Low-dimensional platinum diselenide (PtSe₂) is a promising candidate for high-performance optoelectronics in the short-wavelength mid-infrared band due to its high carrier mobility, excellent stability, and tunable bandgap. However, light usually interacts moderately with low-dimensional PtSe₂, limiting the optoelectronic responses of PtSe₂-based devices. Here we demonstrated a giant optical absorption of a PtSe₂-on-silicon waveguide by integrating a ten-layer PtSe₂ film on an ultra-thin silicon waveguide. The weak mode confinement in the ultra-thin waveguide dramatically increases the waveguide mode overlap with the PtSe₂ film. Our experimental results show that the absorption coefficient of the PtSe₂-on-silicon waveguide is in the range of 0.0648 dB μm^-1 to 0.0704 dB μm^-1 in a spectral region of 2200 nm to 2300 nm wavelengths. Furthermore, we also studied the optical absorption in an ultra-thin silicon microring resonator. Our study provides a promising approach to developing PtSe₂-on-silicon hybrid optoelectronic integrated circuits.