Fig. 5
From: Active sorting of orbital angular momentum states of light with a cascaded tunable resonator
a Schematic of a generic two-mirror Fabry-Pérot cavity comprising two concave mirrors. The radii of curvature are marked in the figure. b Stability diagram of the optical cavity. The shaded regions indicate the stable cavity regions. The hyperbola bounding the shaded regions represents g1g2 = 1
