Based on an array detector, a new heterodyne detection system, which can correct the mismatches of amplitude and phase between signal and local oscillation (LO) beams, is presented in this paper. In the light of the fact that, for a heterodyne signal, there is a certain phase difference between the adjacent two samples of analog-to-digital converter (ADC), we propose to correct the spatial phase mismatch by use of the time-domain phase difference. The corrections can be realized by shifting the output sequences acquired from the detector elements in the array, and the steps of the shifting depend on the quantity of spatial phase mismatch. Numerical calculations of heterodyne efficiency are conducted to confirm the excellent performance of our system. Being different from previous works, our system needs not extra optical devices, so it provides probably an effective means to ease the problem resulted from the mismatches.
Due to quantum confinement and edge effects, graphene quantum dots (GQDs) demonstrate numerous novel chemical/physical properties. Doping GQDs with heteroatoms is an effective way to tailor their electronic and optical properties. However, due to different synthesis methods, the potential use of GQDs doped with heteroatoms is hindered by the poor understanding of their intrinsic optical properties and mechanisms. Recently, we studied optical properties of GQDs by employing theoretical calculations, which can reveal optical mechanisms of GQDs. In this work, optical spectra, HOMO–LUMO gap, and electronic density of GQDs are calculated to reveal electron transition processes. The recombination of electron-hole pairs can result in enhanced absorption intensity. It is expected that this work will provide valuable knowledge for understanding electronic and optical properties of GQDs and give important insights for the development of methods to controllably synthesize GQDs.
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