Ultrasensitive Bidirectional Photoresponse SnSe 2 Photodetector Integration with Thin‐Film Lithium Niobate Photonics

Photodetectors (PDs) based on 2D materials are promising for photonics integration, offering fast response times, high responsivities, and low‐noise detection across a wide range of wavelengths. Here, a novel PD structure consisting of a 35‐nm‐thick SnSe 2 layer covering a proton‐exchanged thin‐film lithium niobate (TFLN) waveguide is presented. This device displays ultrasensitive bidirectional photoresponse characteristics at various wavelengths and can detect photon energies below the SnSe 2 bandgap. Under irradiation at 850 and 450 nm, the device exhibits a positive photoresponse driven by the photoconductive effect, achieving high responsivity of 761.78 A W −1 (0.95 nW) and 694.91 A W −1 (2.125 nW), respectively. Conversely, under irradiation at 1550 and 1310 nm, the device exhibits a negative photoresponse driven by the bolometric effect. The responsivity and response/recovery times under 1550 nm irradiation are measured to be 3.13 A W −1 (578 nW) and 21.3/20.4 ms, respectively. The PD exhibits one of the highest responsivities reported for 2D material‐integrated waveguide PDs. This high‐performance SnSe 2 /TFLN waveguide PD has broad potential for application in optical communication and multifunctional photonic circuits in the visible to near‐infrared (NIR) band.