Gallium nitride micro-light-emitting diode structured light sources for multi-modal optical wireless communications systems

Abstract

<jats:p>Gallium nitride-based light-emitting diodes (LEDs) have revolutionized the lighting industry with their efficient generation of blue and green light. While broad-area (square millimetre) devices have become the dominant LED lighting technology, fabricating LEDs into micro-scale pixels (micro-LEDs) yields further advantages for optical wireless communications (OWC), and for the development of smart-lighting applications such as tracking and imaging. The smaller active areas of micro-LEDs result in high current density operation, providing high modulation bandwidths and increased optical power density. Fabricating micro-LEDs in array formats allows device layouts to be tailored for target applications and provides additional degrees of freedom for OWC systems. Temporal and spatial control is crucial to use the full potential of these micro-scale sources, and is achieved by bonding arrays to pitch-matched complementary metal-oxide-semiconductor control electronics. These compact, integrated chips operate as digital-to-light converters, providing optical signals from digital inputs. Applying the devices as projection systems allows structured light patterns to be used for tracking and self-location, while simultaneously providing space-division multiple access communication links. The high-speed nature of micro-LED array devices, combined with spatial and temporal control, allows many modes of operation for OWC providing complex functionality with chip-scale devices.</jats:p> <jats:p>This article is part of the theme issue ‘Optical wireless communication’.</jats:p>

Dual-color dynamic anti-counterfeiting labels with persistent emission after visible excitation allowing smartphone authentication

“…Fundamentally, to excite the phosphors with the smartphone flashlight, the absorption (PL excitation) spectra of the phosphors must coincide with the flashlight spectra. Most smartphone flashlights are based on an indium gallium nitride light-emitting diode (LED), with an emission peak at 450 nm 40 . Some of the blue light is converted to longer wavelengths by phosphors in the coating of the LED which leads to the observed white light color.…”

Optical wireless communication

“…The major limitation of these devices is the low optical output power, but arrays of micro LEDs can be used to overcome this limitation. This issue features a review article by Dawson et al, who have been pioneering the development of micro LEDs for high-speed VLC [11]. Various laser devices such as vertical-cavity surface-emitting lasers (VCSELs) operating in the infrared spectrum have also been used to build high-speed OWC links.…”

44‐1: Invited Paper: Micro‐LEDs for Technological Convergence between Displays, Optical Communications, and Sensing and Imaging Systems

“…Micro-LED technology is also setting performance benchmarks in LiFi [3,4], and the exciting prospect is emerging of combining micro-LED based capabilities for displays with lighting and communications, potentially also involving sensing, ranging and imaging functions. Thus micro-LEDs are poised to offer new convergences between hitherto largely disparate areas of technology and application [5].…”