Humboldt-Universität zu Berlin - Mathematisch-Naturwissen­schaft­liche Fakultät - Institut für Physik

Institutskolloquium: Prof. Dr. Harald Schwefel (The Dodd-Walls Centre for Photonic and Quantum Technologies, Department of Physics, University of Otago, Dunedin, New Zealand) spricht zum Thema:
Optical Frequency combs and lasing upside-down

Abstract

Legend has it that the ring of power was forged at Mount Doom – Middle Earth (New Zealand). I will show how we strive to harness the power of light bound in crystalline ring resonators [1] realising optical frequency combs, connecting future quantum computers to quantum networks as well as lasing. The magic lies in the nonlinear interaction of matter with the light.
Strong nonlinear interactions require high optical fields. One of the most successful platforms for harvesting strong nonlinear interactions with continuous wave pumping fields are optical
resonators. Large optical fields require long confinement times and small mode volumes. A particular successful system for nonlinear interactions is that of a whispering gallery mode (WGM) resonator. In such a resonator type the light is confined within a dielectric by total internal reflection at its circular dielectric boundary. The confinement by total internal reflection allows modes to exist throughout the transparency region of the material. This broadband confinement combined with the tight guiding of the modes at the rim of the resonator is ideal for nonlinear interaction between different frequency domains or for resonantly enhanced lasing feedback.
In this talk I will present our recent results of optical frequency combs [2] and dual frequency combs [3]. Furthermore, we investigate lasing from titanium doped sapphire WGMs [4] and the seemingly trivial effect that a close by dielectric perturbance has [5].

1. I. Breunig, "Three-wave mixing in whispering gallery resonators," Laser Photonics Rev. 10, 569---587 (2016).
2. A. Rueda, F. Sedlmeir, M. Kumari, G. Leuchs, and H. G. L. Schwefel, "Resonant electro-optic frequency comb," Nature 568, 378--381 (2019).
3. N. J. Lambert, L. S. Trainor, and H. G. L. Schwefel, "An ultra-stable microresonator-based electrooptic dual frequency comb," ArXiv210811140 Phys. (2021).
4. F. Azeem, L. S. Trainor, A. Gao, M. Isarov, D. V. Strekalov, and H. G. L. Schwefel, "Ultra-Low
Threshold Titanium-Doped Sapphire Whispering-Gallery Laser," Adv. Opt. Mater. 10, 2102137 (2022).
5. F. Azeem, L. S. Trainor, P. A. Devane, D. S. Norman, A. Rueda, N. J. Lambert, M. Kumari, M. R.
Foreman, and H. G. L. Schwefel, "Dielectric perturbations: anomalous resonance frequency shifts in optical resonators," Opt. Lett. 46, 2477–2480 (2021).

Das Kolloquium wird "hybrid" durchgeführt, kann also sowohl im Hörsaal als auch über zoom verfolgt werden. Die Anmeldedaten werden im Vorfeld über die üblichen Mailverteiler versandt oder können unter gd-at-physik.hu-berlin.de erfragt werden.