Next-generation mode division multiplexing (MDM) systems aim to integrate concurrent functionalities within a single optical fiber efficiently. In this work, we report on harnessing MDM to simultaneously provide data transmission and power delivery over a two-mode fiber (TMF). We deployed a 1-km TMF to convey a 1 Gbps on-off keying (OOK) data signal and deliver a 17.12 mW input optical power. Through switching the mode allocation (LP01/LP11 for data/power), we examined the suitability of both integrated communication and PWoF functionalities. During our analysis, we established a robust communication link with 1.933×10−5 bit error rate (BER) using the LP11 mode for communication while simultaneously achieving electrical power delivery of ∼2.75 mW at the receiver side using the LP10 mode. This successful integration proves the feasibility of harnessing the TMF for simultaneous data and power transmission in next-generation integrated systems/networks encompassing communication and power.
Three types of halide-perovskite-based fast-acting fluorescent materials have been demonstrated for high-speed visible light communication. All-inorganic metal-halide perovskite CsPbI3 was utilized to generate red color at 685 nm, and twodimensional (2D) hybrid organic-inorganic halide perovskite nanosheets, (PEA)2PbI4 and (PEA)2PbBr4 (PEA= C8H9NH3), with peak photoluminescence (PL) wavelengths of 525 nm and 408 nm, were respectively used for green- and blue-light emission. The materials were then embedded in the polymethyl methacrylate (PMMA) to improve their durability and flexibility in practical applications. Pumped by a 405-nm violet laser, the red and green phosphors exhibit –3-dB modulation bandwidths of 14 MHz and 193 MHz, respectively. For the blue phosphor, a 124-MHz –3-dB bandwidth was obtained by using a 375-nm UVA laser diode. Benefitting from either the short PL lifetime or high PL quantum yield, aggregate Gb/s data transmission was achieved in the communication link. Direct current biased optical orthogonal frequency-division multiplexing (DCO-OFDM) modulation scheme was implemented with an adaptive quadrature amplitude modulation (QAM) signal. The transmission net data rates of RGB phosphors are 0.51 Gb/s, 0.93 Gb/s, and 0.43 Gb/s, respectively. The corresponding average bit error ratios are 3.5×10-3, 3.6×10-3, and 3.6×10-3, which are below the 7%-overhead forward error correction (FEC) criterion. Taking advantage of the tunability of the halide perovskite materials covering the whole visible range could further fulfill high-speed color-pure wavelength-division multiplexing by using a single source with multiple luminescent materials emitting light at different wavelengths. Besides, combining luminescent materials with specific colors, simultaneous white-light illumination, and high-speed communication can also be realized.
Fiber-optic distributed acoustic sensor (DAS) has been deployed for real-time monitoring of various physical phenomena. The operational principle of DAS relies on monitoring backscattered light from a fiber while leaving the pump optical pulses to get wasted at the fiber distal end. Here, we report on energy harvesting from the DAS pump optical signal to supply energy to passive devices. In this work, a DAS over a ∼1.1-km single-mode fiber (SMF) detects a 200-Hz vibration event produced by a piezoelectric transducer (PZT) while harvesting a 1.58–mW optical signal to charge a 10-F supercapacitor.
A Si-integrated oxide-nitride deep-ultraviolet photodetector with remarkable photosensitivity is demonstrated. The proposed device topology is realized through the disordered nucleation of β-Ga2O3 crystals on monocrystalline TiN interlayers forming an oxide-nitride vertical heterostructure stack housed on a Si substrate. Spectral responsivity levels of about 240 A/W at illuminating power density levels of around 7.40 μW/cm2 were achieved.
With the growing number of underwater vehicles and devices used for marine environmental monitoring, there is an urgent need for real-time and high-speed underwater wireless communication technologies to transmit huge amounts of data. This poses great challenges to conventional underwater acoustic communication technology due to its low bandwidth and high latency. Therefore, underwater wireless optical communication with high bandwidth and low latency has become a promising technology. To this end, we develop the first underwater optical wireless sensor network prototype in this work. It consists of two sensor nodes and an optical hub. There is a transceiver circuit, a pH sensor, and an integrated temperature, salinity, and conductivity sensor in the sensor nodes enabling real-time underwater environmental monitoring. There are four transceivers facing four sides in the optical hub to implement bi-directional optical wireless communication with the sensor nodes. In a laboratory testbed and a field trial conducted in an outdoor diving pool, 100% packet success rates are achieved between the optical hub and the sensor nodes at a transmission distance of 60 cm. In the field trial, one of the sensor nodes is placed 60 cm away from the optical hub for real-time underwater environmental monitoring. The other sensor node is mounted on a remotely operated vehicle to collect underwater environmental information. This prototype shows great potential in future underwater mobile sensor networks and the underwater Internet of Things.
Thin polymorphic gallium oxide films were grown on c-plane sapphire using pulsed laser deposition. The stacked thin films (ε-Ga2O3 and β-Ga2O3) were sequentially grown under the same conditions but in a different ambience. Our X-ray diffraction measurements and transmission electron microscopy images confirmed a β-Ga2O3/ε-Ga2O3 polymorphic heterostructure with rocking-curve widths of 1.4° (β-Ga2O3 (¯603)) and 0.6° (ε-Ga2O3 (006)). The crystallographic orientation relationships between c-plane sapphire and the heterogeneously nucleated ε-Ga2O3 buffer layer, as well as between the ε-Ga2O3 and β-Ga2O3 heterogeneous layers, were determined. Our study will aid in developing novel deep-ultraviolet optoelectronic devices, such as solar-blind and metal-insulator-semiconductor deep-ultraviolet photodiodes.
There have been recent research advances in AlGaN-based self-assembled nanowires (NWs) as building blocks for ultraviolet (UV) optoelectronics grown by plasma-assisted molecular beam epitaxy. We review the basic growth kinetics on various foundry-compatible-metal/silicon-based substrates and the epistructure design for UV devices. We highlight the use of diffusion-barrier-metal thin film on silicon substrate as a solution to enhance device performance. NWs offer the opportunity to mitigate the detrimental quantum-confined Stark effect (QCSE), which lowers the recombination rate thereby reducing the device efficiency. On the other hand, the polarization-induced doping from the graded composition along NWs can be advantageous for eluding the inefficient doping in AlGaN-based UV devices. Sidewall surface states and the associate passivation treatment, as well as the use of ultrafast electron-microscopy characterization, are crucial investigations in shedding light on device performance under the influence of surface dangling bonds. For investigating the electrical performance of individual NWs and NWs light-emitting diode as a single entity, recent reports based on conductive atomic force microscopy measurements provide fast-prototyping in-process pass-fail evaluation and a means of improving growth for high-performance devices. Stress tests of NWs devices, crucial for reliable operation, are also discussed. Beyond applications in LEDs, an AlGaN-based NWs solar-blind photodetector demonstrated leveraging on the dislocation-free active region, reduced QCSE, enhanced light absorption, and tunable-composition features. The review opens pathways and offers insights for practical realization of AlGaN-based axial NWs devices on scalable and low-cost silicon substrates.
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