Heterogeneous integration of PdSe₂ photodetectors on thin-film lithium niobate waveguides at 1.55 µm

In this work, multilayer PdSe₂ flakes obtained by mechanical exfoliation were heterogeneously integrated onto thin-film lithium niobate (TFLN) proton-exchanged (PE) waveguides and etched ridge waveguides, enabling two types of waveguide-integrated photodetectors. At a wavelength of 1550 nm and a bias voltage of 1 V, the PE-waveguide photodetector achieved a maximum responsivity of 1.83 A/W, together with a specific detectivity (D*) of 4.5 × 10⁸ Jones, and rise and fall times of 9.8 µs and 7.8 µs, respectively. Meanwhile, the ridge-waveguide device also exhibited stable photoresponse, with a responsivity of 47.8 mA/W and a specific detectivity of 2.8 × 10⁷ Jones. Owing to the smoother surface morphology of the PE waveguide, the intrinsic properties of PdSe₂ were better preserved, resulting in enhanced photoresponse. These results underscore the application potential of PdSe₂-TFLN heterogeneously integrated photodetectors in optical communication systems as well as multifunctional TFLN-based photonic chips.