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As an important parameter to determine the transmission characteristics of a Gaussian beam, the beam waist holds a huge impact in laser technology and imaging systems. Although it is necessary to clearly measure the specific value of the beam waist, the traditional measurement steps are complex and easily introduce error in the measurement process. In this work, we propose an effective method using the in-plane spin splitting (IPSS) generated by the photonic spin Hall effect (PSHE) to precisely estimate the beam waist. We establish a highly sensitive propagation model to describe the relationship between the IPSS shifts and the beam waist of an arbitrary linearly polarized light and then combine with the quantum weak measurement system to amplify the IPSS shifts. We reveal that the IPSS shifts are sensitive to the variation of beam waists when the beam is reflected near the Brewster angle. With the huge amplified IPSS shifts (maximum of 1500 microns), the variation of beam waist can be accurately detected, even by propagation amplification alone. Prospectively, our scheme may provide an effective method for accurately determining the Gaussian beam waist of arbitrary polarization.

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An efficient nicotinamide adenine dinucleotide (NADH) regeneration system is of great significance for the application of oxidoreductase-catalyzed reactions. Photochemical regeneration has been a research hotspot in recent years. Graphite carbon nitride (g-C3N4) has important application prospects. However, bulk g-C3N4 (BCN) has some disadvantages that lead to a low catalytic efficiency. Herein, nanoporous g-C3N4 (PCN) was prepared using silica nanoparticles as templates, and the effects of the mass ratio of cyanamide to silica and the particle size of the templates on the structure, optical, and catalytic properties of PCN were investigated. Then, cyanamide was separately co-polymerized with two types of thiophene compounds and imidazole-, benzene-, and quinolone-based compounds, and the effects of the structure and number of aromatic rings introduced into PCN on the properties of catalysts were studied. The results show that PCN had much better catalytic performance than BCN, the initial reaction rate of NADH regeneration could be upgraded from 18.01 to 37.14 mmol/(g·min) after PCN was modified with thiophene compound, and the yield of NADH after 20 min increased from 56.8 to 82.7%. When other aromatic compounds were added in the PCN preparation process, a catalytic performance similar to that of thiophene-modified PCN was acquired.