Cavity-enhanced field-resolved spectroscopy
Femtosecond enhancement cavities1 are key to applications including high-sensitivity linear2–4 and nonlinear5,6 gas spectroscopy, as well as efficient nonlinear optical frequency conversion7–10. Yet, to date, the broadest simultaneously enhanced bandwidths amount to <20% of the central optical frequency8,9,11–15. Here, we present an ultrabroadband femtosecond enhancement cavity comprising gold-coa
