In this paper, the current research of an underwater optical wireless communication (UWOC) network is reviewed first. A hybrid laser diode (LD) and light-emitting diode (LED)-based UWOC system is then proposed and investigated, in which hybrid cluster-based networking with mobility restricted nodes is utilized to improve both the life cycle and throughput of the UWOC network. Moreover, the LEDs are utilized for the coarse alignment, while the LDs are used for high-precision positioning to reduce the difficulty of optical alignment. Finally, challenges and trends for UWOC are pointed out to provide some insight for potential future work of researchers.

The propagation of a filamentary laser beam at an air-glass surface is studied by setting the incident angle satisfying the total reflection condition. The images of the trajectory of the filamentary laser beam inside the sample and the output far-field spatial profiles are measured with varying incident laser pulse energies. Different from the general total reflection, a transmitted laser beam is detected along the propagation direction of the incident laser beam. The energy ratio of the transmitted laser beam depends on the pulse energies of the incident laser beam. The background energy reservoir surrounding the filament core can break the law of total reflection at the air-glass surface, resulting in the regeneration of the transmitted laser beam.

Based on the geometrical optics approximation, we analyze the effects of non-Kolmogorov turbulence on the spiral spectrum of the orbital angular momentum (OAM) of Airy–Schell beams. Our numerical results of Airy–Schell beams on the horizontal path show that the beam spreading due to diffraction is smaller for shorter wavelengths, a smaller OAM quantum number, a larger radius of the main ring, and a higher arbitrary transverse scale in weak turbulence. The oscillation frequency of the mode probability density of Airy–Schell beams in the radial direction is much lower than that of Hankel–Bessel beams. The mode probability densities of Airy–Schell and Hankel–Bessel beams are remarkably dependent on the wavelength and OAM quantum number. In order to improve the mode probability density, Airy–Schell beams with shorter wavelengths and lower OAM quantum numbers may be the better choice, which is diametrically opposite to Hankel–Bessel beams. Our research provides a reasonable basis for selecting light sources and precise tracking.

In this Letter, new concepts of fluorescence phase-change materials and fluorescence phase-change multilevel recording are proposed. High-contrast fluorescence between the amorphous and crystalline states is achieved in nickel- or bismuth-doped Ge2Sb2Te5 phase-change memory thin films. Opposite phase-selective fluorescence effects are observed when different doping ions are used. The fluorescence intensity is sensitive to the crystallization degree of the films. This characteristic can be applied in reconfigurable multi-state memory and other logic devices. It also has likely applications in display and data visualization.