No abstract

A((=))-D, [A((=))](2)-D and [A ((=))](3)-D multi-maleimides and multi-itaconimides bearing electron-donating chromophores display a strong fluorescence quenching due to an intramolecular charge-transfer interaction. The electron-accepting C=C bond plays a key role in the intramolecular quenching. For the isomerization of these multi-itaconimides and Michael additions of these multi-maleimides, their emission behavior is irreversible. For the Diels-Alder additions of these multi-maleimides, their emission behavior is reversible due to the reversible opening and closing of intramolecular charge-transfer pathway. Tris-maleimide TMPA peripherally modified with furfural alcohol displays not only reversible fluorescence behavior but also reversible aggregation behavior.

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Mono‐, bis‐, and trismaleimides (MM‐2, BM‐4, and TM‐6, respectively) bearing electron‐donating chromophores generally displayed strong fluorescence quenching. The quenching mechanism of fluorescence was revealed by electrochemical studies. On the basis of the electrochemical data, an energy level diagram was established for these maleimides. The electron‐donating ability increased in the order of TM‐6 < BM‐4 < MM‐2. The electron‐accepting ability increased in the opposite order, that is, from MM‐2 to BM‐4 to TM‐6. The copolymerization of multimaleimides with diamine could be well monitored by fluorescence spectroscopy. Compared with fluorescence probe techniques, the fluorescence monitoring could directly reflect the consumption of CC bonds. Furthermore, a novel trismaleimide resin was preliminarily studied, in which TM‐6 was a dual‐purpose functional monomer acting not only as a crosslinker but also as an intrinsic fluorophore to monitor its crosslinking or cure process. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 304–313, 2006

We report the generation of biphotons, with a temporal full width at the half maximum (FWHM) of 13.4±0.3 µs and a spectral FWHM of 50±1 kHz, via the process of spontaneous four-wave mixing. The temporal width is the longest, and the spectral linewidth is the narrowest up to date. This is also the first biphoton result that obtains a linewidth below 100 kHz, reaching a new milestone. The very long biphoton wave packet has a signal-to-background ratio of 3.4, which violates the Cauchy-Schwarz inequality for classical light by 4.8 folds. Furthermore, we demonstrated a highly-tunablelinewidth biphoton source and showed that while the biphoton source's temporal and spectral width were controllably varied by about 24 folds, its generation rate only changed by less than 15%. A spectral brightness or generation rate per pump power per linewidth of 1.2×10 6 pairs/(s•mW•MHz) was achieved at the temporal width of 13.4 µs. The above results were made possible by the low decoherence rate and high optical depth of the experimental system, as well as the nearly phasemismatch-free scheme employed in the experiment. This work has demonstrated a high-efficiency ultranarrow-linewidth biphoton source, and has made a substantial advancement in the quantum technology utilizing heralded single photons.