| Two-dimensional（2D）materials have opened up new boulevard for rapid development of optics,electrics and magnetics,owing to its unique physical properties.Recently,the 2D materials family has been expanding constantly,and their fascinating inherent nature and various potential application prospects are contemporary research hotspots.Among them,the physical and chemical properties of the 2D anisotropic material vary with the crystal orientation,thus the characteristics are distinct and rich.However,there is a lack of anisotropic 2D materials that can stably exist in the air,which greatly limits the further development of 2D materials in polarization-sensitive photonic devices,thermal imaging,and biomimetic synapses.In this paper,the purpose of research is to explore anisotropic 2D materials with high air stability.We successfully prepared high-quality,high-yield,large-area and novel 2D palladium diselenide（PdSe2）through the gold-assisted method.Optical microscope,atomic force microscope,and transmission electron microscope were utilized to display the atomically single-crystal structure of PdSe2.Theoretical calculations and polarization-resolved Raman were used to determine the layer numbers,crystal orientation and strong anisotropy of such material.The unique linear dichroism conversion behavior and high linear dichroic absorption ratio（αy/αx（?）1.11,1.15 and 0.84）of PdSe2 were observed for the first time by polarization-resolved absorption spectroscopy,thereby realizing the design of a polarization-sensitive photodetector with relatively high photocurrent ratio(Imax/Imin=2.94).Based on the excellent linear optical properties,a home-built I-scan system was used to further study the nonlinear optical properties of PdSe2.The strong second harmonic generation could be detected only in even-numbered layers,contrary to other 2D materials.Additionally,the two-photon absorption coefficients of 1-3 layers（β～4.16×105,2.58×105,and 1.51×105cm/GW）are larger by two or three orders of magnitude,compared with that of the conventional 2D materials.Giant modulation depths（αs～32%,27%,and 24%）of saturation absorption were obtained in 1-3 layers PdSe2,which have yet been achieved in other 2D materials.The research results have been published in Nature Communications.Herein,the linear and nonlinear optical characteristics of the novel PdSe2 were comprehensively investigated for the first time.Based on its unique intrinsic physical characteristics,a high-efficiency homogeneous pn junction transistor and a polarization-sensitive photodetector were constructed,which brings new possibilities for the application of linear,nonlinear and quantum optics,and provides new opportunities for the design of high-performance nano-optoelectronic devices in the future. |
