分类： 光学 >> 量子光学 提交时间： 2023-02-19
摘要： Locally chiral light (LCL) is a promising tool for probing and controlling molecular chirality. The pioneering tricolor LCLs' degrees of chirality (DOCs) change periodically in space and vanish by integrating over the whole spatial period, making them cease to be globally effective (i.e., globally achiral). Locally and globally chiral light (LGCL) is a type of more efficient LCL whose DOCs survive by integrating but still change periodically in space. Here, we propose a scheme to generate a new type of LCL called uniformly locally chiral light (ULCL). ULCLs are globally chiral and have spatially uniform DOCs, which makes them superior to current types of LCLs in studies of chiral molecules. By applying the ULCLs in an optical molecular-chirality switch, the racemic mixtures can be converted to enantiopure samples without size restrictions, where the perfect control of molecular chirality with a global efficiency of $100\%$ is predicted, which is twice that of LGCLs. Our work potentially constitutes the starting point for developing more efficient chiroptical techniques for probing and controlling molecular chirality.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
摘要： We theoretically investigate the spectral caustics of high-order harmonics in solids. We analyze the 1-dimension model of solids HHG and find that, apart from the caustics originated from the van Hove singularities in the energy-band structure, another kind of catastrophe singularities also emerge when the different branches of electron-hole trajectories generating high-order harmonics coalesce into a single branch. We solve time-dependent Schr\"odinger equation in periodic potential and demonstrate the control of this kind of singularities in HHG with the aids of two-color laser fields. The diffraction patterns of the harmonic spectrum near the caustics agree well with the inter-band electron-hole recombination trajectories predicted by the semiconductor semi-classical equation. This work is expected to help to understand the HHG dynamics in solids and manipulate the harmonic spectrum by adjusting driving field parameters.
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