About us

Resonant Optics

Welcome to the Resonant Optics research group within the Physics Department of the University of Otago and as part of the Dodd-Walls Centre for Photonic and Quantum Technologies. Our team is lead by Associate Professor Harald Schwefel. Our research is centered around resonantly enhanced nonlinear interactions. Currently we investigate optical frequency combs, coherent microwave to optics conversion, and other fundamental aspects.

Optical Resonators

High quality optical resonators can confine, store, and therefore intensify light on a very small foot-print. Of particular interest to us are resonators based on the Whispering Gallery Mode (WGM) concept. Our group is known to make some of the world’s highest quality WGM resonators. We like to address some fundamental questions with analytical and numerical solutions associated with such optical resonators.

Nonlinear Optics

One of the central interests currently is to use these resonators to enhance the optical field in order to stimulate strong nonlinear interactions. These interactions can lead to the generation of new colours of light (e.g. through second harmonic generation) or to the mixing of two different frequencies (e.g. sum-frequency generation). We use these effects to generate optical frequency combs and to coherently convert microwave and THz radiation into the optical domain. Such conversion will be necessary for connecting future superconducting quantum computers as well as novel airborne microwave detectors for mapping the cosmic microwave background and measuring temperature in the atmosphere. In other works we study third harmonic generation and selective coupling as well as some sensing. Some of our Projects are described here

here is a link to the old version of our website

Recent Posts

Harald gives a presentation online on Waves and nonlinear wave mixing in high quality optical resonators at KOZwaveinar …

Harald been elected as OPTICA Fellow

Harald been selected as OPTICA Senior Member

We hit the cover on Advanced Optical Materials


Lasers and Telecommunication

High quality resonators can enhance Lasers and generate Frequency Combs for Telecommunication

Nonlinear and Quantum Optics

Through a coherent nonlinear interaction different frequency domains can be connected.


High quality Resonators can be used to detect very small changes in the surrounding.

THz Domain

Linear and Nonlinear interaction of THz radiation


We thank all of our funding agencies


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