Mixed orbital angular momentum amplitude shift keying through a single hologram

The orbital angular momentum (OAM) of a photon describes the helical wavefront of a beam, and has recently attracted much attention due to their potential applications in diverse domains. OAM offers a new dimension, which can be encoded as various data symbols for a data-transmission system. Meanwhile, such encoding can be done simultaneously with other encodings as amplitude shift keying, for instance, the mixed OAM-amplitude shift keying (OAM-ASK), to increase further the encoding efficiency. Here we propose an OAM-ASK based data-transmission system, where the data encoding is realized by a single hologram. Additionally, the encoded data can be decoded perfectly through a single hologram too. As a proof-of-concept, we transmit a gray-scale image in free-space through octal OAM with binary amplitude (totally 4 bit per symbol), and 32-ary OAM with quaternary amplitude (totally 7 bit per symbol) over 10 meters. The favorable experimental results show 0 bit-error-rate. This work opens a new insight in mixed OAM-ASK and will inspire various applications.