Velocity-free event-triggered control for a class of uncertain axis-motion systems with prescribed performance.

This paper investigates the fixed-time prescribed performance control problem for a class of axis-motion servo systems subject to the external disturbances and parameter uncertainties. To eliminate the requirement for velocity measurements in the control process, an auxiliary observer is first designed to reconstruct the velocity signal of the controlled plant. Subsequently, an error transformation procedure incorporating a prescribed performance index is integrated into the control system architecture. To overcome the limitations of periodic control design, a robust event-triggered controller is developed, ensuring that the dynamic error of the closed-loop system exhibits fixed-time convergence. Through rigorous theoretical analysis and proofs, it is demonstrated that the proposed event-triggered strategy guarantees Zeno-behavior-free operation. Finally, simulation results are presented to validate the effectiveness of the proposed control algorithm.

Micro-LED with red-green-blue super-pixel integration for simultaneous display and optical near field communication.

This work presents a novel all-in-one Micro-LED pixel (µLEDP) technology by integrating red-green-blue super-pixels (RGBSP) in a single unit cell. Measurement results show that the proposed µLEDP delivers excellent optical and electrical characteristics, including wide color gamut (109% NTSC), wide correlated color temperature range (2831.7-10016.8 K), and high modulation system bandwidth (58-62 MHz). To the best of our knowledge, the proposed integrated µLEDP achieves the highest data rate compared to published results based on other multi-color low-capacitance high-bandwidth LEDs. The maximum simulated non-return-to-zero (NRZ) and 4-level pulse-amplitude-modulation (PAM-4) data rates of 0.3-Gb/s and 1.1-Gb/s, respectively.

CMOS monolithic photodetector with a built-in 2-dimensional light direction sensor for laser diode based underwater wireless optical communications.

Underwater wireless optical communications (UWOC) are considered an emerging high-speed wireless network for underwater applications and compete with underwater radio frequency (RF) communications and underwater acoustic communications (UAC). Even though the utilization of laser diodes (LDs) enhances the -3dB modulation bandwidth extraordinarily from a few tens of MHz to GHz, LDs have the features of high collimation and narrow spectrum. Without the point-to-point optical alignment, the performance of the LD-based UWOC system drops exponentially because the received optical power determines the signal-to-noise ratio (SNR) of the UWOC system. To achieve a high-performance and reliable UWOC link based on LDs requires focusing optics and an alignment system. In this paper, we demonstrated a CMOS monolithic photodetector with a built-in 2-dimensional light direction sensor for the UWOC link by using a 450 nm LD and none-return-to-zero on-off keying (NRZ-OOK) modulation method. Employing this innovative technique, the field of view (FOV) was enlarged to 120°, and data rates up to 110 Mb/s at a bit error rate (BER) of 2.3×10-10 were obtained. The establishment of a proposed UWOC physical link showed enhanced communication performance for more practical and robust wireless communication applications.

Micro-light-emitting diodes with quantum dots in display technology.

Micro-light-emitting diodes (µ-LEDs) are regarded as the cornerstone of next-generation display technology to meet the personalised demands of advanced applications, such as mobile phones, wearable watches, virtual/augmented reality, micro-projectors and ultrahigh-definition TVs. However, as the LED chip size shrinks to below 20 µm, conventional phosphor colour conversion cannot present sufficient luminance and yield to support high-resolution displays due to the low absorption cross-section. The emergence of quantum dot (QD) materials is expected to fill this gap due to their remarkable photoluminescence, narrow bandwidth emission, colour tuneability, high quantum yield and nanoscale size, providing a powerful full-colour solution for µ-LED displays. Here, we comprehensively review the latest progress concerning the implementation of µ-LEDs and QDs in display technology, including µ-LED design and fabrication, large-scale µ-LED transfer and QD full-colour strategy. Outlooks on QD stability, patterning and deposition and challenges of µ-LED displays are also provided. Finally, we discuss the advanced applications of QD-based µ-LED displays, showing the bright future of this technology.

4 Mb/s under a 3 m transmission distance using a quantum dot light-emitting diode and NRZ-OOK modulation.

We realize signal transmission with a miniature light source fabricated by a $4\; {\rm mm}^2 $4mm2 red-emissive CdSe/ZnS quantum-dot light-emitting diode (QLED) in visible light communication (VLC). The light emitted from the 60°-designed QLED transmits in free space with a data rate of 4 Mb/s at a 3 m transmission distance by using a simple modulation scheme of non-return-to-zero on-off keying. The maximum data rate of 2.5 Mb/s with a bit error rate below the forward-error-correction (FEC) limit is achieved with the optical angles of ${\rm \pm 20}^\circ $±20∘. The influences caused by the voltage, distance, and optical angle of emitting light are taken into consideration during communication. The performance of the QLED-based light source compares favorably with other solution-processed devices in efficiency, luminance, bandwidth, transmission speed, and distance. Additionally, to the best of our knowledge, this is the first report of an investigation on the application of QLED in VLC. Our results should be instructive for further investigation on QLED communication.