650-nm vertical-cavity surface-emitting lasers (VCSELs) for plastic optical fiber communication.

Vertical-cavity surface-emitting lasers (VCSELs) are widely used as light sources for high-speed communications. This is mainly due to their economical cost, high bandwidth, and scalability. However, efficient red VCSELs with emissions at 650 nm are required for plastic optical fiber (POF) technology because of the low-loss transmission window centered around this wavelength.

Multifunctional difluoroboron β-diketonate-based luminescent receiver for a high-speed underwater wireless optical communication system.

The last decade has witnessed considerable progress in underwater wireless optical communication in complex environments, particularly in exploring the deep sea. However, it is difficult to maintain a precise point-to-point reception at all times due to severe turbulence in actual situations. To facilitate efficient data transmission, the color-conversion technique offers a paradigm shift in large-area and omnidirectional light detection, which can effectively alleviate the étendue limit by decoupling the field of view and optical gain.

Wide-field-of-view optical detectors for deep ultraviolet light communication using all-inorganic CsPbBr perovskite nanocrystals.

Optical wireless communication (OWC) links suffer from strict requirements of pointing, acquisition, and tracking (PAT) between the transmitter and receiver. Extending the narrow field-of-view (FoV) of conventional light-focusing elements at the receiver side can relax the PAT requirements. Herein, we use all-inorganic CsPbBr nanocrystals (NCs) to extend various optical concentrators' FOV to 60°, regardless of the original FOV values of the concentrators.

Metal-Organic Frameworks in Mixed-Matrix Membranes for High-Speed Visible-Light Communication.

Mixed-matrix membranes (MMMs) based on luminescent metal-organic frameworks (MOFs) and emissive polymers with the combination of their unique advantages have great potential in separation science, sensing, and light-harvesting applications. Here, we demonstrate MMMs for the field of high-speed visible-light communication (VLC) using a very efficient energy transfer strategy at the interface between a MOF and an emissive polymer. Our steady-state and ultrafast time-resolved experiments, supported by high-level density functional theory calculations, revealed that efficient and ultrafast energy transfer from the luminescent MOF to the luminescent polymer can be achieved.

Chlorine-Infused Wide-Band Gap p-CuSCN/n-GaN Heterojunction Ultraviolet-Light Photodetectors.

Copper thiocyanate (CuSCN) is a p-type semiconductor that exhibits hole-transport and wide-band gap (∼3.9 eV) characteristics. However, the conductivity of CuSCN is not sufficiently high, which limits its potential application in optoelectronic devices.

All-inorganic halide-perovskite polymer-fiber-photodetector for high-speed optical wireless communication.

The use of optical carrier frequencies will enable seamless data connection for future terrestrial and underwater internet uses and will resolve the technological gap faced by other communication modalities. However, several issues must be solved to propel this technological shift, which include the limitations in designing optical receivers with large detection areas, omnidirectionality, and high modulation bandwidth, mimicking antennas operating in the radio-frequency spectrum. To address this technological gap, herein, we demonstrate halide-perovskite-polymer-based scintillating fibers as a near-omnidirectional detection platform for several tens-to-hundreds of Mbit/s optical communication in both free space and underwater links.

A flexible capacitive photoreceptor for the biomimetic retina.

Neuromorphic vision sensors have been extremely beneficial in developing energy-efficient intelligent systems for robotics and privacy-preserving security applications. There is a dire need for devices to mimic the retina's photoreceptors that encode the light illumination into a sequence of spikes to develop such sensors. Herein, we develop a hybrid perovskite-based flexible photoreceptor whose capacitance changes proportionally to the light intensity mimicking the retina's rod cells, paving the way for developing an efficient artificial retina network.

Single-Crystalline All-Oxide α-γ-β Heterostructures for Deep-Ultraviolet Photodetection.

Recent advancements in gallium oxide (GaO)-based heterostructures have allowed optoelectronic devices to be used extensively in the fields of power electronics and deep-ultraviolet photodetection. While most previous research has involved realizing single-crystalline GaO layers on native substrates for high conductivity and visible-light transparency, presented and investigated herein is a single-crystalline β-GaO layer grown on an α-AlO substrate through an interfacial γ-InO layer. The single-crystalline transparent conductive oxide layer made of wafer-scalable γ-InO provides high carrier transport, visible-light transparency, and antioxidation properties that are critical for realizing vertically oriented heterostructures for transparent oxide photonic platforms.

Gbit/s ultraviolet-C diffuse-line-of-sight communication based on probabilistically shaped DMT and diversity reception.

We demonstrated a high-speed 1×2 single-input and multiple-output (SIMO) diffuse-line-of-sight (diffuse-LOS) ultraviolet-C (UVC) solar-blind communication link over a distance of 5 meters. To approach the Shannon limit and improve the spectral efficiency, we implemented probabilistically shaped discrete multitone modulation. As compared to a single-input and single-output (SISO) counterpart, we observed significant improvement in the SIMO link in terms of the angle of view of the receiver and the immunity to emulated weather condition.

Toward self-powered and reliable visible light communication using amorphous silicon thin-film solar cells.

Enhancing robustness and energy efficiency is critical in visible light communication (VLC) to support large-scale data traffic and connectivity of smart devices in the era of fifth-generation networks. To this end, we demonstrate that amorphous silicon (a-Si) thin-film solar cells with a high light absorption coefficient are particularly useful for simultaneous robust signal detection and efficient energy harvesting under the condition of weak light in this study. Moreover, a first-generation prototype called AquaE-lite is developed that consists of an a-Si thin-film solar panel and receiver circuits, which can detect weak light as low as 1 µW/cm.

Ultraviolet-to-blue color-converting scintillating-fibers photoreceiver for 375-nm laser-based underwater wireless optical communication.

Underwater wireless optical communication (UWOC) can offer reliable and secure connectivity for enabling future internet-of-underwater-things (IoUT), owing to its unlicensed spectrum and high transmission speed. However, a critical bottleneck lies in the strict requirement of pointing, acquisition, and tracking (PAT), for effective recovery of modulated optical signals at the receiver end. A large-area, high bandwidth, and wide-angle-of-view photoreceiver is therefore crucial for establishing a high-speed yet reliable communication link under non-directional pointing in a turbulent underwater environment.

High-speed colour-converting photodetector with all-inorganic CsPbBr perovskite nanocrystals for ultraviolet light communication.

Optical wireless communication (OWC) using the ultra-broad spectrum of the visible-to-ultraviolet (UV) wavelength region remains a vital field of research for mitigating the saturated bandwidth of radio-frequency (RF) communication. However, the lack of an efficient UV photodetection methodology hinders the development of UV-based communication. The key technological impediment is related to the low UV-photon absorption in existing silicon photodetectors, which offer low-cost and mature platforms.

On the realization of across wavy water-air-interface diffuse-line-of-sight communication based on an ultraviolet emitter.

We experimentally demonstrated high-speed diffuse line-of-sight optical wireless communication across a wavy water-air-interface. The testbed channel was evaluated, in terms of data rate, coverage and robustness to the dynamic wave movement, based on the performance of different modulation schemes, including non-return-to-zero on-off keying (NRZ-OOK) and quadrature amplitude modulation (QAM)-orthogonal frequency division multiplexing (OFDM). Under the emulated calm water condition, 8-QAM-OFDM offers a data rate of 111.

Deep-Ultraviolet Photodetection Using Single-Crystalline β-GaO/NiO Heterojunctions.

In recent years, β-GaO/NiO heterojunction diodes have been studied, but reports in the literature lack an investigation of an epitaxial growth process of high-quality single-crystalline β-GaO/NiO thin films via electron microscopy analysis and the fabrication and characterization of an optoelectronic device based on the resulting heterojunction stack. This work investigates the thin-film growth of a heterostructure stack comprising n-type β-GaO and p-type cubic NiO layers grown consecutively on -plane sapphire using pulsed laser deposition, as well as the fabrication of solar-blind ultraviolet-C photodetectors based on the resulting p-n junction heterodiodes. Several characterization techniques were employed to investigate the heterostructure, including X-ray crystallography, ion beam analysis, and high-resolution electron microscopy imaging.

Perovskite-Based Artificial Multiple Quantum Wells.

Semiconductor quantum well structures have been critical to the development of modern photonics and solid-state optoelectronics. Quantum level tunable structures have introduced new transformative device applications and afforded a myriad of groundbreaking studies of fundamental quantum phenomena. However, noncolloidal, III-V compound quantum well structures are limited to traditional semiconductor materials fabricated by stringent epitaxial growth processes.

High-power blue superluminescent diode for high CRI lighting and high-speed visible light communication.

We demonstrated a high-power (474 mW) blue superluminescent diode (SLD) on c-plane GaN-substrate for speckle-free solid-state lighting (SSL), and high-speed visible light communication (VLC) link. The device, emitting at 442 nm, showed a large spectral bandwidth of 6.5 nm at an optical power of 105 mW.