Ultracompact Orbital Angular Momentum Sorter on a CMOS Chip.

On-chip integrated orbital angular momentum (OAM) sorting is of great importance in tackling the severe challenge of exponential growth in data traffic. Despite the continuous success, current demultiplexing techniques either scarify efficiency dramatically or lose the compactness of a system. Here we experimentally demonstrate an ultracompact OAM sorter using TiO metasurfaces integrated onto a complementary metal-oxide-semiconductor (CMOS) camera. By utilizing the propagation phases, we transfer the unitary transformation theory in bulky systems into two TiO metasurfaces, responsible for the functions of transformation and fan-out beam copying and focusing as well as the functions of phase correction and Fourier transform. The flatform metasurface doublet enables one to integrate the OAM sorter onto a camera chip. Consequently, OAM beams with topological charges of = -3 to 3 were separated by a CMOS camera with an average crosstalk of -6.43 dB. This approach shall shed light on next-generation OAM modes processing.