Van der Waals integration inch-scale 2D MoSe_(2) layers on Si for highly-sensitive broadband photodetection and imaging

As one of the most promising materials for two-dimensional transition metal chalcogenides(2D TMDs),molybdenum diselenide(MoSe_(2))has great potential in photodetectors due to its excellent properties like tunable bandgap,high carrier mobility,and excellent air stability.Although 2D MoSe_(2)-based photodetectors have been reported to exhibit admired performance,the large-area 2D MoSe_(2)layers are difficult to be achieved via conventional synthesis methods,which severely impedes its future applications.Here,we present the controllable growth of large-area 2D MoSe_(2)layers over 3.5-inch with excellent homogeneity by a simple post-selenization route.Further,a high-quality n-MoSe_(2)/p-Si van der Waals(vdW)heterojunction device is in-situ fabricated by directly growing 2D n-MoSe_(2)layers on the patterned p-Si substrate,which shows a self-driven broadband photoresponse ranging from ultraviolet to mid-wave infrared with an impressive responsivity of 720.5 mA·W^(−1),a high specific detectivity of 10^(13) Jones,and a fast response time to follow nanosecond pulsed optical signal.In addition,thanks to the inch-level 2D MoSe_(2)layers,a 4×4 integrated heterojunction device array is achieved,which has demonstrated good uniformity and satisfying imaging capability.The large-area 2D MoSe_(2)layer and its heterojunction device array have great promise for high-performance photodetection and imaging applications in integrated optoelectronic systems.

A digitally generated ultrafine optical frequency comb for spectral measurements with 0.01-pm resolution and 0.7-μs response time

Optical spectral measurements are crucial for optical sensors and many other applications,but the prevailing methods,such as optical spectrum analysis and tunable laser spectroscopy,often have to make compromises among resolution,speed,and accuracy.Optical frequency combs are widely used for metrology of discrete atomic and molecular spectral lines.However,they are usually generated by optical methods and have large comb spacing,which limits the resolution for direct sampling of continuous spectra.To overcome these problems,this paper presents an original method to digitally generate an ultrafine optical frequency comb(UFOFC)as the frequency ruler for spectral measurements.Each comb line provides one sampling point,and the full spectrum can be captured at the same time using coherent detection.For an experimental demonstration,we adopted the inverse fast Fourier transform to generate a UFOFC with a comb spacing of 1.46 MHz over a 10-GHz range and demonstrated its functions using a Mach–Zehnder refractive index sensor.The UFOFC obtains a spectral resolution of 0.01 pm and response time of 0.7 μs;both represent 100-fold improvements over the state of the art and could be further enhanced by several orders of magnitude.The UFOFC presented here could facilitate new label-free sensor applications that require both high resolution and fast speed,such as measuring binding kinetics and single-molecule dynamics.