A wet-stretching technique was applied to chromophore-blended poly(vinyl alcohol) (PVA) films to control the agglomeration of chromophores and improve the triplet−triplet annihilation (TTA) photon upconversion (UC) performance of the solid-state system. By using the stretching technique, a maximum UC quantum yield of ∼3% and lowest threshold intensity of 90 mW/cm 2 were obtained under atmospheric conditions. It was found that a decrease in the crystallinity of the PVA matrix induced by stretching caused specific localization of the chromophores and accelerated triplet energy transfer and triplet exciton migration.

No abstract

A method suggested by Holevo is used to obtain a lower bound for the information capacity of a quantum narrow-band free-space link without extraneous noise. At high photon rates the bound is better than those previously proposed and comes close to a fundamental upper bound. It is not so good at low rates, where it is beaten by photon-detecting systems. The normal modes are not treated as independent channels. A system is describeo where the normal modes are used in pairs.

The mechanical stretching process enhances the upconversion emission of chromophore-blended poly(vinyl alcohol) films under an air atmosphere.