title: Amplified Photon Upconversion by Photonic Shell of Cholesteric Liquid Crystals.
abstract: As an effective platform to exploit triplet-triplet-annihilation-based photon upconversion (TTA-UC), microcapsules composed of a fluidic UC core and photonic shell are microfluidically prepared using a triple emulsion as the template. The photonic shell consists of cholesteric liquid crystals (CLCs) with a periodic helical structure, exhibiting a photonic band gap. Combined with planar anchoring at the boundaries, the shell serves as a resonance cavity for TTA-UC emission and enables spectral tuning of the UC under low-power-density excitation. The CLC shell can be stabilized by introducing a polymerizable mesogen in the LC host. Because of the microcapsule spherical symmetry, spontaneous emission of the delayed fluorescence is omnidirectionally amplified at the edge of the stop band. These results demonstrate the range of opportunities provided by TTA-UC systems for the future design of low-threshold photonic devices.
authors.forename: Ji-Hwan
authors.initials: JH
authors.lastname: Kang
authors.affiliation: Department of Chemical and Biomolecular Engineering, KAIST , Daejeon 305-701, South Korea.
authors.forename: Shin-Hyun
authors.identifier: 0000-0003-4095-5779
authors.initials: SH
authors.lastname: Kim
authors.forename: Alberto
authors.initials: A
authors.lastname: Fernandez-Nieves
authors.forename: Elsa
authors.identifier: 0000-0002-8205-8016
authors.initials: E
authors.lastname: Reichmanis