A p‐Quinodimethane‐Bridged Porphyrin Dimer

A p‐quinodimethane (p‐QDM)‐bridged porphyrin dimer 1 has been prepared for the first time. An unexpected Michael addition reaction took place when we attempted to synthesize compound 1 by reaction of the cross‐conjugated keto‐linked porphyrin dimers 8 a and 8 b with alkynyl/aryl Grignard reagents. Alternatively, compound 1 could be successfully prepared by intramolecular Friedel–Crafts alkylation of the diol‐linked porphyrin dimer 14 with concomitant oxidation in air. Compound 1 shows intense one‐photon absorption (OPA, λ_max=955 nm, ε=45400 M ^?1 cm^?1) and a large two‐photon absorption (TPA) cross‐section (σ⁽²⁾_max=2080 GM at 1800 nm) in the near‐infrared (NIR) region due to its extended π‐conjugation and quinoidal character. It also exhibits a short singlet excited‐state lifetime of 25 ps. The cyclic voltammogram of 1 displays multiple redox waves with a small electrochemical energy gap of 0.86 eV. The ground‐state geometry, electronic structure, and optical properties of 1 have been further studied by density functional theory (DFT) calculations and compared with those of the keto‐linked dimer 8 b . This research has revealed that incorporation of a p‐QDM unit into the porphyrin framework had a significant impact on its optical and electronic properties, leading to a novel NIR OPA and TPA chromophore.     

半导体上转换单光子探测技术研究进展

近年来,量子通信技术取得了卓越的进步和发展,而作为接收端的单光子探测器在其通信系统中则起着至关重要的作用.本文聚焦于当前主流的半导体单光子探测器,就其器件原理、工作模式、优势和劣势等方面进行了相关评述.在此基础上,着重介绍了本课题组所提出的一种新型半导体近红外上转换单光子探测技术（USPD）的研究进展.从USPD的器件基本原理、器件结构、性能指标等方面阐述了其优越性和可行性,并给出了USPD最新的空间光耦合实验结果.半导体上转换单光子探测技术的关键特性在于它不是采用InP雪崩层结构实现信号的放大,而是利用成熟的硅单光子雪崩二极管（Si-SPAD）器件来实现信号的放大和采集,从而规避InP结构在暗计数率和后脉冲效应方面的问题.USPD利用半导体材料,通过外加电场将近红外光子上转换为短波近红外或者可见光子,再用商用Si-SPAD进行探测的方法,也为我们提供了一种单光子探测的新思路,打开了另一扇单光子探测的窗口.