Fig. 2
From: Universal orbital angular momentum spectrum analyzer for beams
The schematic experimental setup to demonstrate the universal OAM spectrum analyzer. DFB, Distributed feedback laser; SMF, single mode fiber; Col., collimator; HWP1 & HWP2, half wave plates; PBS, polarized beam splitter; SLM, liquid-crystal spatial light modulator; L1 & L2, a beam expender consists of concave and convex lenses with the focal length f1 = − 50 mm and f2 = 200 mm separately; R, reflector; LR, liquid-crystal retarder; BS, non-polarized beam splitter; CCD, infrared CCD camera