Promotionsvortrag Physik: „Thermodynamics for Advancing and Controlling Brillouin Scattering“

Ankündigung des Promotionsvortrags von: Herrn Andreas Geilen

In our modern world, light is increasingly utilized for communication, signal processing, and sens-ing. Concepts based on stimulated Brillouin scattering (SBS) contribute to this development by allowing light to manipulate light, using acoustic phonons as a mediator, or to probe the acoustic phonons directly. In this thesis, different materials and methods to improve and tailor the Brillouin gain and phonon lifetime by an order of magnitude have been developed and experimentally demonstrated in the analysis of liquid-core optical fiber (LiCOF) and in an optoacoustic memory, respectively.

First, the sealed LiCOF design allows high pressures above 1000 bar, while using only minute amounts (nL) of the liquid under test, a method that is not limited to CS2. With the gained knowledge of the relationship between temperature and pressure, the meta-stable regime of ab-solute negative pressure is reliably reached and pressures below 300 bar are generated and an-alyzed.

Second, a cryogenic setup was developed and built to cool down optical fibers to 4.2 K. This is used to implement a Brillouin-based memory in HNLF at cryogenic temperatures, revealing an order of magnitude increase in the intrinsic phonon lifetime. The results allow for a direct local measurement of the acoustic lifetime. The proposed technique can be combined with existing schemes and opens new possibilities to apply Brillouin scattering for all optical data processing.

(Vortrag auf Englisch)

Dem Vortrag schließt sich eine Diskussion von 15 Minuten an. Vortrag und Diskussion sind öffentlich. Diesen Verfahrensteilen folgt ein nicht öffentliches Rigorosum von 45 Minuten.