Highly sensitive broadband photodetector based on PtSe2 photothermal effect and fiber harmonic Vernier effect.

Platinum diselenide (PtSe2), a two-dimensional material, has shown exceptional promise in photodetection applications because of its air stability, high carrier mobility, and layer-tunable bandgap. However, conventional photoconductive modes face challenges with high dark currents. To address this limitation, all-optical fiber detection technology with high sensitivity and response, has emerged as a promising approach for developing PtSe2, based devices. In this study, a high-sensitivity broadband photodetector based on PtSe2 with a cascaded Fabry-Pérot interferometer (FPI) is proposed, which utilises the broad spectral absorption property of PtSe2 and the interference enhancement mechanism of cascaded F-P cavities to achieve high-sensitivity broadband photodetection. The experimental results show that the detector has excellent spectral response in the 808-1,550 nm band, with a sensitivity of 3.867 nm/mW at 980 nm and a response time of 37.43 ms/129.17 ms. The sensitivity at 1,550 nm is up to 134.014 nm/mW, with a response time of 75.74 ms/28.66 ms. The double matching of 0.8 eV energy and PtSe2 material, which is situated in the range of the material intrinsic absorption peak (1,200-1,600 nm), is responsible for the excellent sensitivity at 1,550 nm. It is also highly matched with the interband jump energy level, which generates more hot carriers per unit optical power and thereby increases the photothermal conversion efficiency. This study provides a new solution for the design of high-sensitivity, ultra-wideband optical fiber photodetectors, which has important potential applications in optical communications, environmental monitoring, and sensing.