Vienna University of Technology

About: Vienna University of Technology is a education organization based out in Vienna, Austria. It is known for research contribution in the topics: Laser & Context (language use). The organization has 16723 authors who have published 49341 publications receiving 1302168 citations.

All-Optical Switch and Transistor Gated by One Stored Photon

Abstract: The realization of an all-optical transistor, in which one “gate” photon controls a “source” light beam, is a long-standing goal in optics. By stopping a light pulse in an atomic ensemble contained inside an optical resonator, we realized a device in which one stored gate photon controls the resonator transmission of subsequently applied source photons. A weak gate pulse induces bimodal transmission distribution, corresponding to zero and one gate photons. One stored gate photon produces fivefold source attenuation and can be retrieved from the atomic ensemble after switching more than one source photon. Without retrieval, one stored gate photon can switch several hundred source photons. With improved storage and retrieval efficiency, our work may enable various new applications, including photonic quantum gates and deterministic multiphoton entanglement.

Controlled Arrangement of Nanoparticle Arrays in Block-Copolymer Domains

Abstract: This Review describes recent results on the precise spatial distribution control of metal and semiconductor nanoparticles into domains of microphase-separated block copolymers. Specific focus is directed towards selective incorporation into a specific microphase of a block copolymer. Details on theoretical aspects concerning nanoparticle incorporation as well as practical examples are given. Furthermore, examples on applications and technological aspects of the resulting nanoparticle/polymer nanocomposites are provided.

Ab initio calculation of the lattice dynamics and phase diagram of boron nitride

Abstract: We present a detailed study of the lattice dynamics and of the phase stability of cubic zincblende (c-BN) and hexagonal (h-BN) boron nitrides. The phonon-dispersion relations at different densities are calculated using a first-principles force-constant method. The calculated eigenfrequencies and phonon Gr\"uneisen parameters are in good agreement with experimental findings. From the electronic and vibrational energies as a function of volume we calculate the phase $(p,T)$ diagram of boron nitride in a quasiharmonic approximation. At low temperature c-BN is the stable modification; the c-BN/h-BN coexistence line intersects the temperature axis at 1440 K. In experiments this temperature lies between 1200 and 1800 K. Anharmonic corrections improve the agreement between the calculation and experiment for high pressure and temperature.