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Resonant Optics


Group Leader: Associate Professor Harald Schwefel

Traditionally light cannot change its colour. Only at very high intensities can the light interact with its surrounding and generate all kinds of new colours. To get to these high field strengths with low power lasers, optical resonators, which trap light, are the key. Our group specialises in fabricating some of the world’s best ultra-high-quality optical resonators for a variety of different applications.

Connecting frequency domains
One of our current central interests is to use these resonators to enhance the optical field in order to stimulate strong nonlinear interactions. These interactions can lead to mixing of two different frequencies (sum-frequency generation) with which we coherently convert microwave and THz radiation into the optical domain. This conversion can preserve the quantum characteristics of the interacting fields and will be useful for connecting future superconducting quantum computers. Such interaction can also be used as novel airborne microwave detectors for mapping the cosmic microwave background and measuring temperature in the atmosphere. Another area we are working on is frequency combs, where the generated light contains many equally-spaced frequency components. In a more fundamental research we focus on connecting the near infrared domain with the visible light through third-order parametric down conversion.

High quality sensing
One side effect of ultra-high-quality optical resonators is their very sharp frequency response. Such a response is strongly affected by the environment. With this we can probe temperature, pressure and the surrounding material extremely precisely. We study these effects theoretically, numerically, and experimentally.

Find out more about our research here