Fig. 2: Monolithic electro-optic cavity design.

a Measured time-domain intra-cavity fields, for quartz cavity lengths of 92, 82, 56, and 44 µm. Nominal deposited gold thickness for all samples is 10 nm. Standard error is represented here, and in panels (b–d) as a lighter area. b Cavity spectra corresponding to the cavity fields in panel (a) offset according to the cavity length. The intersections (blue ticks) of the computed cavity dispersions (light blue) with the experimental baselines (horizontal gray lines) highlight the perfect agreement to the experimental mode peaks (vertical gray lines). The gray regions are excluded to suppress zero-crossings of the cavity correction function. (c) Measured time-domain intra-cavity fields of a 44 µm-long quartz cavity for nominal deposited gold thicknesses of 14, 12, 10, 8 nm. d Cavity spectra corresponding to the fields in panel (c) including the mode-specific quality factors for the 14 nm Au mirror cavity (top trace). e Intra-cavity peak fields (black dots) and quality factors (blue dots) of the 3.3 THz mode (dashed line in (d)), as a function of the gold layer thickness. The dashed lines are derived from electromagnetic modeling