Efficient generation and sorting of orbital angular momentum eigenmodes of light by thermally tuned q-plates

We present methods for generating and for sorting specific orbital angular momentum (OAM) eigenmodes of a light beam with high efficiency, using a liquid crystal birefringent plate with unit topological charge known as "q-plate." The generation efficiency has been optimized by tuning the optical retardation of the q-plate with temperature. The measured OAM m=+-2 eigenmodes generation efficiency from an input TEM00 beam was of 97%. Mode sorting of the two input OAM m = +-2 eigenmodes was achieved with an efficiency of 81%.