Encoding and decoding of digital spiral imaging based on bidirectional transformation of light's spatial eigenmodes

Digital spiral imaging has been demonstrated as an effective optical tool to encode optical information and retrieve topographic information of an object. Here we develop a conceptually new and concise scheme for optical image encoding and decoding toward free-space digital spiral imaging. We experimentally demonstrate that the optical lattices with l = +/- 50 orbital angular momentum superpositions and a clover image with nearly 200 Laguerre-Gaussian (LG) modes can be well encoded and successfully decoded. It is found that an image encoded/decoded with a two-index LG spectrum (considering both azimuthal and radial indices, l and p) possesses much higher fidelity than that with a one-index LG spectrum (only considering the l index). Our work provides an alternative tool for the image encoding/decoding scheme toward free-space optical communications. (C) 2016 Optical Society of America