Detuning-assisted cavity enhancement in spectroscopy

Cavity-enhanced spectroscopy is a widely used experimental technique. We show that detuning the cavity frequency from the transition of interest can enhance the precision for dipole moment estimation by up to two orders of magnitude beyond the improvement when the cavity is resonant with the transition. We show this for both classical continuous-wave (CW) and pulsed single-photon probes, even in the presence of losses. We trace this enhancement to a detuning-controlled redistribution of information between the light- and matter-like polaritons, with losses determining the optimal branch. We show that this enhancement remains accessible using conventional photodetection and time-correlated single-photon counting.