Fig. 1: Device principles and design.
From: Microresonator-based electro-optic dual frequency comb
a Effective electro-optic coefficient of LiNbO3 for axial and radial modes as a function of angle from the crystallographic z-axis, showing the angular dependency. b Cartoon of our device, with the LiNbO3 ring embedded in a toroidal loop gap. A gap in the outer of the cavity provides for optical access via prism coupling. c Left—half cross-section of the device in b. Centre—expanded view of LiNbO3 resonator and the gap of the loop-gap resonator. Right—expanded view of the edge of the resonator and cavity, showing COMSOL simulations of the optical and microwave field intensities. d Microwave spectrum of the cavity, tuned to critical coupling. e Optical mode spectrum for radial (upper) and axial (lower) modes. Free spectral ranges (FSRs) are arrowed.
