Fig. 1: Schematic description of the experimental system.

a The plasma-containing microcavity. b–g Calculated transmission through the fibre-coupled plasma resonator as a function of changes in the plasma’s absorption (b–d) and refractive index (e–g). We assume Lorentzian resonance absorption. Absorption-induced transmission is evident in (b–d), as indicated by the green lines and arrow in (b, c). Absorption-induced effects are symmetrical with detuning, as indicated by the blue and red lines and arrows in (b, d). On the contrary, index-induced effects for blue or red detuning are different, as indicated by the blue and red lines and arrows in (e–g).