Figure 2: All-optical devices based on a degenerate cavity system.
From: Synthetic-lattice enabled all-optical devices based on orbital angular momentum of light
(a) The main (red) and auxiliary (brown) cavities are coupled by a pair of beam splitters (BSs), both cavities are degenerate. Two spatial light modulators (SLMs) are used to change photon’s OAM by ±M. (b) The input/output port realized as a pinhole at the centre of a mirror to couple the l=0 mode in and out.
