Figure - available from: Optics Express
This content is subject to copyright. Terms and conditions apply.
(a) Experiment of the proposed VLC system. IFFT: inverse fast-Fourier-transformed (IFFT); DAC: digital-to-analog converter, APD: avalanche photodiode; AWG: arbitrary waveform generator; RTO: real-time oscilloscope; ADC: analog-to-digital converter. Photographs of (b) the experiment and (c) APD based Rx.
Source publication
We propose and implement a high-bandwidth white-light visible light communication (VLC) system accomplishing data rate of 2.805 Gbit/s utilizing a semipolar blue micro-LED. The system uses an InGaN/GaN semipolar (20-21) blue micro-LED to excite yellow phosphor film for high-speed VLC. The packaged 30 μm 2 × 4 blue micro-LED array has an electrical-...
Similar publications
Subcarrier Index Modulation is an OFDM variant that provides superior power and band-width efficiency. In this paper, we present a novel, double-sided pulse interval modulation (DS-PIM)-based SIM OFDM technique. The proposed technique exploits the variable symbol size of DPIM to provide a variable sub-block size and enable dynamic assignment of sub...
Citations
... Nowadays, the GaN material has attracted growing interest in the fields of illumination, power devices, and visible communication due to its high carrier mobility, high refractive index, and high nonlinearity coefficient [11,12]. Especially, many recent studies have proved simultaneous emission and detection function of the InGaN/GaN multi-quantum well (MQW) structures [13,14], which facilitates multiple components fabricated on a single chip, such as the monolithic integration of light emitting diode (LED), PD, modulator, and waveguide [15,16]. ...
This Letter reports a collinear optical interconnect architecture for acoustic sensing via a monolithic integrated GaN optoelectronic chip. The chip is designed with a ring-shaped photodiode (PD) surrounding a light-emitting diode (LED) of a spectral range from 420–530 nm. The axisymmetric structure helps the coaxial propagation of light transmission and reception. By placing this multiple-quantum wells (MQW)-based device and a piece of aluminum-coated polyethylene terephthalate (Al/PET) film on fiber ends, an ultra-compact acoustic sensing system is built. The sound vibrations can be simply detected by direct measurement of the diaphragm deformation-induced power change. An average signal noise ratio (SNR) of 40 dB and a maximum sensitivity of 82 mV/Pa are obtained when the acoustic vibration frequency changes from 400 Hz to 3.2 kHz. This work provides a feasible solution to miniaturize the sensing system footprint and reduce the cost.
... The literature on GaN-based PD has highlighted several structures, including metal-semiconductor-metal structures (MSM) [15][16][17], 2D structures [10][11][12]14], and multi-quantum-wells (MQWs) [18,19]. Among them, MQWs are commonly seen in LED/micro-LED devices and a considerable amount of literature has been published on large bandwidth micro-LED transmitters devices [20][21][22]. Hence, it inspires researchers to design PD based on LED/micro-LED devices in VLC systems, taking advantage such as the low cost, low complexity, and ubiquitous presence in the illumination system. ...
In this paper, we studied a series of high-speed photodetectors (PD) with different super-lattice interlayer periods and the scale of the effective area to examine their communication performance. The mini-PDs are designed with a single 1 mm × 1 mm effective area. The mini-PDs have three different super-lattice (SL) periods in the interlayer: 8, 15, and 32. The micro-PD sample has multiple 50um by 50um photosensitive areas that form a 4 × 4 receiver array, which shares a common N electrode. Its SL period is 26. The experiment shows that mini-PDs have the advantages such as better tolerance to beam spot deviation, larger field of view (FoV), higher responsibility, and wider peak width in spectral response. But micro-LED samples outperform the others in communication capacity and wavelength selectivity. The 8, 15, and 32 SL mini-PD samples achieve 6.6, 7.3, and 8.8 Gb/s data rates, respectively. The micro-PD gains the maximum data rate of 14.38Gb/s without applying waveform level post-equalization, and 15.26Gb/s after using an NN-based post-equalizer. This experiment shows that with proper DSP, GaN-based PD would be suitable for high-speed VLC systems, especially for the short wavelength spectrum in visible light.
... 124,125 There are three primary ways to modify light emission wavelength: through phosphors, using quantum dots (QDs), or by changing the compound semiconductor layer itself. [126][127][128][129] These techniques are discussed in detail in Sec. IV C. The wavelength of the light emitted from the microLEDs is also an important factor for optogenetic stimulations. ...
... 122 Recently, Chang et al. reported a white light VLC system that used semi-polar blue microLEDs and yellow phosphors to achieve a data rate of 2.805 Gbps. 128 The higher data rate and bandwidth of the system are attributed to the improved radiative efficiency of the semi-polar blue microLEDs resulting from the reduced quantum-confined Stark effect (QCSE). ...
MicroLEDs offer an extraordinary combination of high luminance, high energy efficiency, low cost, and long lifetime. These characteristics are highly desirable in various applications, but their usage has, to date, been primarily focused toward next-generation display technologies. Applications of microLEDs in other technologies, such as projector systems, computational imaging, communication systems, or neural stimulation, have been limited. In non-display applications which use microLEDs as light sources, modifications in key electrical and optical characteristics such as external efficiency, output beam shape, modulation bandwidth, light output power, and emission wavelengths are often needed for optimum performance. A number of advanced fabrication and processing techniques have been used to achieve these electro-optical characteristics in microLEDs. In this article, we review the non-display application areas of the microLEDs, the distinct opto-electrical characteristics required for these applications, and techniques that integrate the optical and electrical components on the microLEDs to improve system-level efficacy and performance.
... With the continuous development in the field of display technology, the nitride-based μ light-emitting diodes (μLEDs) have been evaluated for wide applications, such as the low-power consume wearable devices [1], wide-viewing angle outdoor displaying and televisions [2,3], high-speed wireless visible light communication [4,5], and high-resolution augmented/virtual reality (AR/VR) products [6]. For high pixels per inch (PPI) display, the size of μLED pixel size needs to shrink to below 20 μm. ...
Generally, the inductively coupled plasma-reactive ion etching (ICP-RIE) mesa technology was used to remove p-GaN/MQWs and expose n-GaN for electrical contact in a fabricated micro light-emitting diode (μLED). In this process, the exposed sidewalls were significantly damaged which result in small-sized μLED presenting a strong size-dependent influence. Lower emission intensity was observed in the μLED chip, which can be attributed to the effect of sidewall defect during etch processing. To reduce the non-radiative recombination, the ion implantation using an As ⁺ source to substitute the ICP-RIE mesa process was introduced in this study. The ion implantation technology was used to isolate each chip to achieve the mesa process in the μLED fabrication. Finally, the As ⁺ implant energy was optimized at 40 keV, which exhibited excellent current–voltage characteristics, including low forward voltage (3.2 V @1 mA) and low leakage current (10 –9 A@− 5 V) of InGaN blue μLEDs. The gradual multi-energy implantation process from 10 to 40 keV can further improve the electrical properties (3.1 V @1 mA) of μLEDs, and the leakage current was also maintained at 10 –9 A@− 5 V.
... Referring to the design method of filters, Min et.al proposed a novel equalization circuit design process and realized 1.35 Gb/s data rates with 600 MHz bandwidth using phosphor-coated LEDs [15]. In addition to using equalization technologies to expand the bandwidth of LEDs, there have been many researches on high-speed LED devices in recent years [16][17][18]. Chang et.al implemented 2.805 Gb/s phosphor white light visible light communication utilizing an InGaN/GaN semipolar blue micro-LED [16], and the micro-LED array has an electrical-to-optical (EO) bandwidth of 1042.5 MHz. ...
Due to narrow bandwidth and slow yellow light, it is difficult for visible light communication (VLC) systems based on high-power phosphor-coated light-emitting diodes (LEDs) to support high data rates. In this paper, a novel transmitter based on a commercial phosphor-coated LED is proposed, which can achieve a wideband VLC system without a blue filter. The transmitter consists of a folded equalization circuit and a bridge-T equalizer. The folded equalization circuit is based on a new equalization scheme and can expand the bandwidth of high-power LEDs more significantly. The bridge-T equalizer is used to reduce the influence of the slow yellow light generated by the phosphor-coated LED, which is more suitable than blue filters. Utilizing the proposed transmitter, the 3 dB bandwidth of the VLC system using the phosphor-coated LED is extended from several megahertz to 893 MHz. As a result, the VLC system can support real-time on-off keying non-return to zero (OOK-NRZ) data rates up to 1.9 Gb/s at a distance of 7 m with a bit error rate (BER) of 3 × 10⁻⁵.
... Both of them employ a simple On-Off Keying (OOK) modulation. A performance improvement can be achieved at the expense of more complex modulation/demodulation approaches: in [11] quaternaryamplitude-shift-keying (4-ASK) modulation allowed a 20-fold performance increase with respect to OOK; in [12] 2.8 Gb/s at 12 cm are obtained with a blue microled and Orthogonal Frequency Division Multiplexing (OFDM) modulation [13]; in [14] wavelength division multiplexing (WDM) applied to a RGB LED allowed 3.4 Gb/s at 10 cm. ...
... These are the typical characteristics required, for example, when the data communication is performed through LEDs simultaneously employed for lighting as well, like in vehicular [10] or indoor applications. Data channels targeted to higher bandwidths [12] would require a modification of the front-end. ...
Visible Light Communication (VLC) employs the modulation of light energy to establish a data connection at a short range. The end-to-end data latency is a significant concern due to the ever-increasing constraints imposed by new applications and standards like 6G. To enhance data rate and communication distance, researchers are proposing more calculation-demanding modulation/demodulation techniques. However, implementing these techniques in real-time and ultra-low latency environments is challenging. In this paper, the authors propose an open system that integrates a programmable VLC front-end with a robust back-end based on a Field Programmable Gate Array (FPGA) to address this challenge. The front-end can drive LEDs with up to 1 A over a bandwidth of 0.01 – 10 MHz and is programmed via an easy MATLAB interface. With the FPGA framework, users can implement various low-latency VLC applications by modifying a minimal part of the code. The system is demonstrated by implementing two applications: a 1.56 Mb/s link based on chirp coding and a 100 kb/s link based on Manchester modulation that complies with IEEE 802.15.7. In both cases, the bit latency was under 50 μs, and transmission errors were not detected when the input SNR was greater than 1 and -2 dB, respectively.
... Recently, by reducing the size to the micron scale, with lateral dimensions less than 100 µm, micro-LEDs present better −3 dB bandwidth up to a few hundred MHz [7,8]. Sun et al. [9] reported GaN-based blue LEDs with a 75 µm diameter, exhibiting a −3 dB modulation bandwidth of 225.4 MHz and a light output power of 1.6 mW at the current of 35 mA. ...
Over the past few decades, GaN-based LEDs have been widely used in solid-state lighting (SSL) due to their energy-saving and long-lifetime characteristics. However, the limited modulation bandwidth of conventional commercial LED chips limits their application in a high-speed visible light communication (VLC) system. Herein, this work designs vertical parallel micro-LED arrays with different array numbers to develop LED sources for communication and lighting. The as-prepared micro-LEDs in a 2 × 2 array reveal a high modulation bandwidth of ∼785 MHz at 6.67 kA/cm². Meanwhile, the light output power is over 7 mW, which is more suitable for VLC in free space.
... Thus, blue μLEDs exhibit the highest reported modulation bandwidth among all wavelength devices. Currently, c-plane μLEDs have a lower band-width than nonpolar or semipolar μLEDs; however, bandwidths greater than 1 GHz can be achieved by structural optimization or growth of microstructures 86,90,95,96 . In addition, the use of QDs as active regions also helps reduce the carrier lifetime of the device 91,93 . ...
With the rapid growth of mobile communication data in recent years, visible light communication (VLC) technology based on GaN LEDs can cope with spectrum crises. However, as a light source device, the modulation bandwidth (MB) and light output power (LOP) are not ideal, which hinders communication quality and system reliability. This work proposes the high-reliability graphene (Gr)/GaN-based micro-light-emitting diodes (micro-LEDs) arrays with an LOP of 46 mW and a high
$-$
3-dB MB of 610 MHz at the current density of 6.7 kA/cm
$^{\text{2}}$
. The various layers of Gr were adopted to increase carrier radiative recombination rate and current spreading in the quantum wells, which can effectively increase the reliability and LOP, as well as reduce the aging of LOP. With the appropriate layers of Gr, hole injection was enhanced and current expansion was improved accordingly, increasing the MB of the micro-LEDs. Possessing high MB, the micro-LEDs arrays also achieved high LOP and low aging rate under high temperature and humidity conditions by introducing the appropriate number of Gr layers, which will be beneficial to improve the lifespan and reliability of the micro-LEDs. The optimistic results in this letter possess high potential of providing high LOP and MB light sources in VLC system.
Optical wireless communication (OWC) is an emerging area where research and development are growing worldwide. The radio-frequency (RF) spectral resource in traditional communication band has been exhausted, and frequency allocation will be a big issue, particularly for the future 6G networks. The non-terrestrial-networks (NTN) in 6G introduce new applications, such as automatic logistics with drones, satellite communication, underwater communication, etc, making OWC inevitable for such ultra-broadband and secure wireless transmissions. This tutorial covers the recent advances and future perspectives in OWC, free-space-optical (FSO) communication and sensing, from devices to applications.
