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Octave-spanning tunable parametric oscillation in crystalline Kerr microresonators


Parametric nonlinear optical processes allow for the generation of new wavelengths of coherent electromagnetic radiation. Their ability to create radiation that is widely tunable in wavelength is particularly appealing, with applications ranging from spectroscopy to quantum information processing. Unfortunately, existing tunable parametric sources are marred by deficiencies that obstruct their widespread adoption. Here, we show that ultrahigh-Q crystalline microresonators made of magnesium fluoride can overcome these limitations, enabling compact and power-efficient devices capable of generating clean and widely tunable sidebands. We consider several different resonators with carefully engineered dispersion profiles, achieving hundreds of nanometres of sideband tunability in each device. In addition to direct observations of discrete tunability over an optical octave from 1,083 nm to 2,670 nm, we record signatures of mid-infrared sidebands at almost 4,000 nm. The simplicity of the demonstrated devices—compounded by their remarkable tunability—paves the way for low-cost, widely tunable sources of electromagnetic radiation.

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The data that support the plots within this paper and other findings of this study are available from the corresponding author upon reasonable request.


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This work was supported by the Marsden Fund, Rutherford Discovery Fellowships and James Cook Fellowships of the Royal Society of New Zealand.

Author information

N.L.B.S. performed all the experiments. T.B. and V.N. performed numerical modelling of the resonators and helped perform the delayed self-heterodyne linewidth measurements. L.S.T. and H.G.L.S. fabricated the resonators. M.E. and S.C. contributed to theoretical interpretation of the results. M.E. and S.G.M. wrote the manuscript. All authors contributed to discussing and interpreting the results.

Correspondence to Stuart G. Murdoch.

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This file contains more information about the work and Supplementary Figs. 1–3.

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Fig. 1: Scheme description and resonator modelling.
Fig. 2: Experimental set-up and illustrative results.
Fig. 3: Experimental observations of octave-tunability and signatures of mid-IR sidebands.
Fig. 4: Proof-of-concept demonstration of continuous sideband tunability.