Optics and Photonics Seminar: Nonlinear Optics in Diamond Microcavities

Monday, 01. July 2024 // 13.00 -

HU Department of Physics

Zum Großen Windkanal 2, 12489 Berlin
Lecture Hall 2.049

Dr. Sigurd Flågan
University of Calgary, Canada

Nonlinear Optics in Diamond Microcavities

The centrosymmetric nature of the diamond lattice prohibits second-order optical nonlinear processes, which limits pristine diamond to the study of third-order nonlinear interactions. However, introducing crystal defects can break the crystal symmetry, thus allowing for nonlinear second-order processes. In this work, we demonstrate cavity-enhanced second-harmonic generation from a diamond microdisk cavity, which we attribute to the presence of NV centres. We further show strong photoinduced suppression of the second-harmonic generated signal by off-resonant optical excitation of the NV centres. This quenching effect can be explained by nonlinear charge-state conversion from the negative to the neutral charge-state mediated by a strong IR cavity field. From this, we infer that the neutral charge-state possesses a comparatively smaller second-order nonlinearity compared to the negative charge-state.

If time allows, I will present an alternative platform for realising tuneable nonlinear optics based on a diamond membrane embedded in an open, fully-tuneable Faby-Perot microcavity. The resonance frequency of such a hybrid cavity platform depends on the exact combination of diamond thickness and airgap thickness. By exploiting a slight thickness gradient of the diamond membrane, we harness the nonlinear mode dispersion and demonstrate ∼THz continuous tuning of double-resonant Raman scattering^[1].

^{[1] S. Flågan, P. Maletinsky, R. J. Warburton, D. Riedel., Optica 9, 1197-1209 (2022)}