A robust basis for multi-bit optical communication with vectorial light

Increasing the information capacity of communication channels is a pressing need, driven by growing data demands and the consequent impending data crunch with existing modulation schemes. In this regard, mode division multiplexing (MDM), where the spatial modes of light form the encoding basis, has enormous potential and appeal, but is impeded by modal noise due to imperfect channels. Here we overcome this challenge by breaking the existing MDM paradigm of using the modes themselves as a discrete basis, instead exploiting the polarization inhomogeneity (vectorness) of vectorial light as our information carrier. We show that this encoding basis can be partitioned and detected almost at will, and measured in a channel independent fashion, a fact we confirm experimentally using atmospheric turbulence as a highly perturbing channel example. Our approach replaces conventional amplitude modulation with a novel modal alternative for potentially orders of magnitude channel information enhancement, yet is robust to fading even through noisy channels, offering a new paradigm to exploiting the spatial mode basis for optical communication.