Festschrift 25 Jahre Fachgebiet Maschinenelemente und Mechanik, Technische Hochschule Darmstadt

Festschrift 25 Jahre Fachgebiet Maschinenelemente und Mechanik, Technische Hochschule Darmstadt Leiter Prof. Dr.-Ing. Walter Raab. Kolloquium am 13. September 1991, Darmstad

Acousto-Optic Modulation in Ambient Air

Control over intensity, shape, direction and phase of coherent light is a cornerstone of 20 photonics. Modern laser optics, however, frequently demands parameter regimes where either the wavelength or the optical power restricts control e.g. due to absorption or damage. Limitations are imposed by the properties of solid media, upon which most photonic control schemes rely. We propose to circumvent these limitations using gas media tailored by high-intensity ultrasound waves. We demonstrate a first implementation of this approach by modulating ultrashort laser 25 pulses using ultrasound waves in ambient air, entirely omitting transmissive solid media. At peak powers of 20 GW exceeding the limits of solid-based acousto-optical modulation by about three orders of magnitude, we reach a diffraction efficiency greater than 50% while preserving excellent beam quality. Our results open a route towards versatile gas-phase Sono-Photonic methods, i.e. gas-based photonic systems controlled by sonic waves.Comment: 20 pages, including 11 pages of main text and 9 pages of supplementary text, 3 figures, 3 supplemtary figures, 1 supplementary tabl

Poly(para-phenyleneethynylene)s as emtters in polymer LEDs

11 different dialkoxy- and dialkyl-poly(para-phenyleneethynylene)s (PPEs) featuring novel branched and literature described linear and branched side chains were prepared using a Sonogashira coupling. The side chains were of different length and branching character. The degree of polymerization of the PPEs ranged from Pn = 44–343 with polydispersities ranging from 1.5–3.1. Fairly simple OLED-stacks with up to three layers (electron injection, emitter layer, and hole injection) were produced. Depending upon the PPEs’ structure and the stack architecture but particularly the thickness of the emitting PPE-layer, a large increase in brightness up to 2.2 � 103 cd m�2 was observed, a significant improvement over earlier reported values

Festschrift 25 Jahre Fachgebiet Maschinenelemente und Mechanik, Technische Hochschule Darmstadt

Festschrift 25 Jahre Fachgebiet Maschinenelemente und Mechanik, Technische Hochschule Darmstadt Leiter Prof. Dr.-Ing. Walter Raab. Kolloquium am 13. September 1991, Darmstad