A Chip-Based Orbital Angular Momentum Receiver for Underwater Optical Communications

In this program, Physical Sciences Inc. (PSI) and Professor Eric. G. Johnson (Clemson University) will develop an integrated optical receiver for underwater communication using orbital angular momentum (OAM) on a silicon-nitride photonics platform. A high-bandwidth underwater optical link is a critical need for underwater communications. An ideal underwater communications link should be compact and robust, capable of high bandwidths with low error-rates and crosstalk to establish a secure link over long distances. An optical communication system operating at visible wavelengths (having minimal water absorption) is an attractive solution as radio-frequencies are unable to deeply penetrate water and acoustic systems are low-bandwidth. The large bandwidths and high directionality of laser-based systems are a promising alternative, however, Gaussian beam systems suffer from scattering due to turbidity, aberrations from turbulence, and other obstructions (e.g. bubbles). OAM modes have been shown to be more resilient to turbidity and turbulence than Gaussian beams, are also more secure, and can be spatially multiplexed for increased bandwidth. This effort will focus on reducing the size, weight, and power requirements, increasing the receiver’s sensitivity, and making the system robust and mass-producible targeting a bandwidth of 2 Gbs/s at distances of >500 m.