Real-time underwater wireless optical communication and positioning an integrated system based on angular diversity SiPMs.

Underwater communication and positioning are essential for autonomous underwater vehicle (AUV) docking and formation. The traditional methods for communication and positioning are mainly independent from each other, increasing the redundancy and integration difficulty for AUVs. In this Letter, we demonstrate a real-time underwater wireless optical communication and positioning (UWOCP) integrated system. The LED array is adopted as a light source, and the pulse-position modulation (PPM) is used for a maximum transmission and sensing distance. By employing the silicon photomultiplier (SiPM) array, which consists of five SiPMs with different angles, the high sensitivity and ability to distinguish angles are obtained. Through calculating the relationship between the received pulse signal intensity of the five SiPMs, the pitch angle and yaw angle can be obtained. The experimental results in the pool show that the Ethernet bandwidth of 2.2 Mbps with an average angular error of 3.08° for one-dimensional positioning can be realized at a 50 m distance. To the best of our knowledge, this is the longest distance at which a real-time UWOCP system has been demonstrated. The proposed UWOCP system has the advantages of high sensitivity, computing efficiency, and compact structure, presenting great potential for underwater applications.

Broadband unidirectional transverse light scattering in a V-shaped silicon nanoantenna.

The efficient manipulation of light-matter interactions in subwavelength all-dielectric nanostructures offers a unique opportunity for the design of novel low-loss visible- and telecom-range nanoantennas for light routing applications. Several studies have achieved longitudinal and transverse light scattering with a proper amplitude and phase balance among the multipole moments excited in dielectric nanoantennas. However, they only involve the interaction between electric dipole, magnetic dipole, and up to the electric quadrupole. Here, we extend and demonstrate a unidirectional transverse light scattering in a V-shaped silicon nanoantenna that involves the balance up to the magnetic quadrupole moment. Based on the long-wavelength approximation and exact multipole decomposition analysis, we find the interference conditions needed for near-unity unidirectional transverse light scattering along with near-zero scattering in the opposite direction. These interference conditions involve relative amplitude and phases of the electromagnetic dipoles and quadrupoles supported by the silicon nanoantenna. The conditions can be applied for the development of either polarization- or wavelength- dependent light routing on a V-shaped silicon and plasmonic nanoantennas.