76
|
Janjua B, Sun H, Zhao C, Anjum DH, Priante D, Alhamoud AA, Wu F, Li X, Albadri AM, Alyamani AY, El-Desouki MM, Ng TK, Ooi BS. Droop-free Al xGa 1-xN/Al yGa 1-yN quantum-disks-in-nanowires ultraviolet LED emitting at 337 nm on metal/silicon substrates. OPTICS EXPRESS 2017; 25:1381-1390. [PMID: 28158020 DOI: 10.1364/oe.25.001381] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/21/2016] [Accepted: 01/12/2017] [Indexed: 06/06/2023]
Abstract
Currently the AlGaN-based ultraviolet (UV) solid-state lighting research suffers from numerous challenges. In particular, low internal quantum efficiency, low extraction efficiency, inefficient doping, large polarization fields, and high dislocation density epitaxy constitute bottlenecks in realizing high power devices. Despite the clear advantage of quantum-confinement nanostructure, it has not been widely utilized in AlGaN-based nanowires. Here we utilize the self-assembled nanowires (NWs) with embedding quantum-disks (Qdisks) to mitigate these issues, and achieve UV emission of 337 nm at 32 A/cm2 (80 mA in 0.5 × 0.5 mm2 device), a turn-on voltage of ~5.5 V and droop-free behavior up to 120 A/cm2 of injection current. The device was grown on a titanium-coated n-type silicon substrate, to improve current injection and heat dissipation. A narrow linewidth of 11.7 nm in the electroluminescence spectrum and a strong wavefunctions overlap factor of 42% confirm strong quantum confinement within uniformly formed AlGaN/AlGaN Qdisks, verified using transmission electron microscopy (TEM). The nitride-based UV nanowires light-emitting diodes (NWs-LEDs) grown on low cost and scalable metal/silicon template substrate, offers a scalable, environment friendly and low cost solution for numerous applications, such as solid-state lighting, spectroscopy, medical science and security.
Collapse
|
77
|
Murali B, Yengel E, Peng W, Chen Z, Alias MS, Alarousu E, Ooi BS, Burlakov V, Goriely A, Eddaoudi M, Bakr OM, Mohammed OF. Temperature-Induced Lattice Relaxation of Perovskite Crystal Enhances Optoelectronic Properties and Solar Cell Performance. J Phys Chem Lett 2017; 8:137-143. [PMID: 27966364 DOI: 10.1021/acs.jpclett.6b02684] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
Hybrid organic-inorganic perovskite crystals have recently become one of the most important classes of photoactive materials in the solar cell and optoelectronic communities. Albeit improvements have focused on state-of-the-art technology including various fabrication methods, device architectures, and surface passivation, progress is yet to be made in understanding the actual operational temperature on the electronic properties and the device performances. Therefore, the substantial effect of temperature on the optoelectronic properties, charge separation, charge recombination dynamics, and photoconversion efficiency are explored. The results clearly demonstrated a significant enhancement in the carrier mobility, photocurrent, charge carrier lifetime, and solar cell performance in the 60 ± 5 °C temperature range. In this temperature range, perovskite crystal exhibits a highly symmetrical relaxed cubic structure with well-aligned domains that are perpendicular to a principal axis, thereby remarkably improving the device operation. This finding provides a new key variable component and paves the way toward using perovskite crystals in highly efficient photovoltaic cells.
Collapse
|
78
|
Zhao C, Ng TK, Tseng CC, Li J, Shi Y, Wei N, Zhang D, Consiglio GB, Prabaswara A, Alhamoud AA, Albadri A, Alyamani AY, Zhang XX, Li LJ, Ooi BS. InGaN/GaN nanowires epitaxy on large-area MoS2 for high-performance light-emitters. RSC Adv 2017. [DOI: 10.1039/c7ra03590j] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
High-quality nitride nanowires on large-area layered transition metal dichalcogenides are first reported, which yielded light-emitting diodes (LEDs) with superior performance.
Collapse
|
79
|
Shen C, Guo Y, Oubei HM, Ng TK, Liu G, Park KH, Ho KT, Alouini MS, Ooi BS. 20-meter underwater wireless optical communication link with 1.5 Gbps data rate. OPTICS EXPRESS 2016; 24:25502-25509. [PMID: 27828488 DOI: 10.1364/oe.24.025502] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
The video streaming, data transmission, and remote control in underwater call for high speed (Gbps) communication link with a long channel length (~10 meters). We present a compact and low power consumption underwater wireless optical communication (UWOC) system utilizing a 450-nm laser diode (LD) and a Si avalanche photodetector. With the LD operating at a driving current of 80 mA with an optical power of 51.3 mW, we demonstrated a high-speed UWOC link offering a data rate up to 2 Gbps over a 12-meter-long, and 1.5 Gbps over a record 20-meter-long underwater channel. The measured bit-error rate (BER) are 2.8 × 10-5, and 3.0 × 10-3, respectively, which pass well the forward error correction (FEC) criterion.
Collapse
|
80
|
Shen C, Lee C, Ng TK, Nakamura S, Speck JS, DenBaars SP, Alyamani AY, El-Desouki MM, Ooi BS. High-speed 405-nm superluminescent diode (SLD) with 807-MHz modulation bandwidth. OPTICS EXPRESS 2016; 24:20281-20286. [PMID: 27607634 DOI: 10.1364/oe.24.020281] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
III-nitride LEDs are fundamental components for visible-light communication (VLC). However, the modulation bandwidth is inherently limited by the relatively long carrier lifetime. In this letter, we present the 405 nm emitting superluminescent diode (SLD) with tilted facet design on semipolar GaN substrate, showing a broad emission of ~9 nm at 20 mW optical power. Owing to the fast recombination (τe<0.35 ns) through the amplified spontaneous emission, the SLD exhibits a significantly large 3-dB bandwidth of 807 MHz. A data rate of 1.3 Gbps with a bit-error rate of 2.9 × 10-3 was obtained using on-off keying modulation scheme, suggesting the SLD being a high-speed transmitter for VLC applications.
Collapse
|
81
|
Janjua B, Ng TK, Zhao C, Oubei HM, Shen C, Prabaswara A, Alias MS, Alhamoud AA, Alatawi AA, Albadri AM, Alyamani AY, El-Desouki MM, Ooi BS. Ultrabroad linewidth orange-emitting nanowires LED for high CRI laser-based white lighting and gigahertz communications. OPTICS EXPRESS 2016; 24:19228-19236. [PMID: 27557202 DOI: 10.1364/oe.24.019228] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Group-III-nitride laser diode (LD)-based solid-state lighting device has been demonstrated to be droop-free compared to light-emitting diodes (LEDs), and highly energy-efficient compared to that of the traditional incandescent and fluorescent white light systems. The YAG:Ce3+ phosphor used in LD-based solid-state lighting, however, is associated with rapid degradation issue. An alternate phosphor/LD architecture, which is capable of sustaining high temperature, high power density, while still intensity- and bandwidth-tunable for high color-quality remained unexplored. In this paper, we present for the first time, the proof-of-concept of the generation of high-quality white light using an InGaN-based orange nanowires (NWs) LED grown on silicon, in conjunction with a blue LD, and in place of the compound-phosphor. By changing the relative intensities of the ultrabroad linewidth orange and narrow-linewidth blue components, our LED/LD device architecture achieved correlated color temperature (CCT) ranging from 3000 K to above 6000K with color rendering index (CRI) values reaching 83.1, a value unsurpassed by the YAG-phosphor/blue-LD counterpart. The white-light wireless communications was implemented using the blue LD through on-off keying (OOK) modulation to obtain a data rate of 1.06 Gbps. We therefore achieved the best of both worlds when orange-emitting NWs LED are utilized as "active-phosphor", while blue LD is used for both color mixing and optical wireless communications.
Collapse
|
82
|
Alias MS, Dursun I, Saidaminov MI, Diallo EM, Mishra P, Ng TK, Bakr OM, Ooi BS. Optical constants of CH 3NH 3PbBr 3 perovskite thin films measured by spectroscopic ellipsometry. OPTICS EXPRESS 2016; 24:16586-16594. [PMID: 27464113 DOI: 10.1364/oe.24.016586] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
The lack of optical constants information for hybrid perovskite of CH3NH3PbBr3 in thin films form can delay the progress of efficient LED or laser demonstration. Here, we report on the optical constants (complex refractive index and dielectric function) of CH3NH3PbBr3 perovskite thin films using spectroscopic ellipsometry. Due to the existence of voids, the refractive index of the thin films is around 8% less than the single crystals counterpart. The energy bandgap is around 2.309 eV as obtained from photoluminescence and spectrophotometry spectra, and calculated from the SE analysis. The precise measurement of optical constants will be useful in designing optical devices using CH3NH3PbBr3 thin films.
Collapse
|
83
|
Zhao C, Ng TK, ElAfandy RT, Prabaswara A, Consiglio GB, Ajia IA, Roqan IS, Janjua B, Shen C, Eid J, Alyamani AY, El-Desouki MM, Ooi BS. Droop-Free, Reliable, and High-Power InGaN/GaN Nanowire Light-Emitting Diodes for Monolithic Metal-Optoelectronics. NANO LETTERS 2016; 16:4616-23. [PMID: 27352143 DOI: 10.1021/acs.nanolett.6b01945] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
A droop-free nitride light-emitting diode (LED) with the capacity to operate beyond the "green gap" has been a subject of intense scientific and engineering interest. While several properties of nanowires on silicon make them promising for use in LED development, the high aspect ratio of individual nanowires and their laterally discontinuous features limit phonon transport and device performance. Here, we report on the monolithic integration of metal heat-sink and droop-free InGaN/GaN quantum-disks-in-nanowire LEDs emitting at ∼710 nm. The reliable operation of our uncooled nanowire-LEDs (NW-LEDs) epitaxially grown on molybdenum was evident in the constant-current soft burn-in performed on a 380 μm × 380 μm LED. The square LED sustained 600 mA electrical stress over an 8 h period, providing stable light output at maturity without catastrophic failure. The absence of carrier and phonon transport barriers in NW-LEDs was further inferred from current-dependent Raman measurements (up to 700 mA), which revealed the low self-heating. The radiative recombination rates of NW-LEDs between room temperature and 40 °C was not limited by Shockley-Read-Hall recombination, Auger recombination, or carrier leakage mechanisms, thus realizing droop-free operation. The discovery of reliable, droop-free devices constitutes significant progress toward the development of nanowires for practical applications. Our monolithic approach realized a high-performance device that will revolutionize the way high power, low-junction-temperature LED lamps are manufactured for solid-state lighting and for applications in high-temperature harsh environment.
Collapse
|
84
|
Bose R, Sun J, Khan JI, Shaheen BS, Adhikari A, Ng TK, Burlakov VM, Parida MR, Priante D, Goriely A, Ooi BS, Bakr OM, Mohammed OF. Real-Space Visualization of Energy Loss and Carrier Diffusion in a Semiconductor Nanowire Array Using 4D Electron Microscopy. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2016; 28:5106-5111. [PMID: 27111855 DOI: 10.1002/adma.201600202] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/13/2016] [Revised: 02/28/2016] [Indexed: 06/05/2023]
Abstract
A breakthrough in the development of 4D scanning ultrafast electron microscopy is described for real-time and space imaging of secondary electron energy loss and carrier diffusion on the surface of an array of nanowires as a model system, providing access to a territory that is beyond the reach of either static electron imaging or any time-resolved laser spectroscopy.
Collapse
|
85
|
Xu X, Zhou J, Jiang L, Lubineau G, Ng T, Ooi BS, Liao HY, Shen C, Chen L, Zhu JY. Highly transparent, low-haze, hybrid cellulose nanopaper as electrodes for flexible electronics. NANOSCALE 2016; 8:12294-306. [PMID: 27270356 DOI: 10.1039/c6nr02245f] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
Paper is an excellent candidate to replace plastics as a substrate for flexible electronics due to its low cost, renewability and flexibility. Cellulose nanopaper (CNP), a new type of paper made of nanosized cellulose fibers, is a promising substrate material for transparent and flexible electrodes due to its potentially high transparency and high mechanical strength. Although CNP substrates can achieve high transparency, they are still characterized by high diffuse transmittance and small direct transmittance, resulting in high optical haze of the substrates. In this study, we proposed a simple methodology for large-scale production of high-transparency, low-haze CNP comprising both long cellulose nanofibrils (CNFs) and short cellulose nanocrystals (CNCs). By varying the CNC/CNF ratio in the hybrid CNP, we could tailor its total transmittance, direct transmittance and diffuse transmittance. By increasing the CNC content, the optical haze of the hybrid CNP could be decreased and its transparency could be increased. The direct transmittance and optical haze of the CNP were 75.1% and 10.0%, respectively, greatly improved from the values of previously reported CNP (31.1% and 62.0%, respectively). Transparent, flexible electrodes were fabricated by coating the hybrid CNP with silver nanowires (AgNWs). The electrodes showed a low sheet resistance (minimum 1.2 Ω sq(-1)) and a high total transmittance (maximum of 82.5%). The electrodes were used to make a light emitting diode (LED) assembly to demonstrate their potential use in flexible displays.
Collapse
|
86
|
Shen C, Ng TK, Leonard JT, Pourhashemi A, Nakamura S, DenBaars SP, Speck JS, Alyamani AY, El-Desouki MM, Ooi BS. High-brightness semipolar (2021¯) blue InGaN/GaN superluminescent diodes for droop-free solid-state lighting and visible-light communications. OPTICS LETTERS 2016; 41:2608-2611. [PMID: 27244426 DOI: 10.1364/ol.41.002608] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
A high-brightness, droop-free, and speckle-free InGaN/GaN quantum well blue superluminescent diode (SLD) was demonstrated on a semipolar (2021¯) GaN substrate. The 447-nm emitting SLD has a broad spectral linewidth of 6.3 nm at an optical power of 123 mW. A peak optical power of 256 mW was achieved at 700 mA CW injection current. By combining YAG:Ce phosphor, SLD-generated white light shows a color-rendering index (CRI) of 68.9 and a correlated color temperature (CCT) of 4340 K. The measured frequency response of the SLD revealed a -3 dB bandwidth of 560 MHz, thus demonstrating the feasibility of the device for both solid-state lighting (SSL) and visible-light communication (VLC) applications.
Collapse
|
87
|
Khan JI, Adhikari A, Sun J, Priante D, Bose R, Shaheen BS, Ng TK, Zhao C, Bakr OM, Ooi BS, Mohammed OF. Nanowires: Enhanced Optoelectronic Performance of a Passivated Nanowire-Based Device: Key Information from Real-Space Imaging Using 4D Electron Microscopy (Small 17/2016). SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2016; 12:2312. [PMID: 27124006 DOI: 10.1002/smll.201670087] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Selective mapping of surface charge carrier dynamics of InGaN nanowires before and after surface passivation with octadecylthiol (ODT) is reported by O. F. Mohammed and co-workers on page 2313, using scanning ultrafast electron microscopy. In a typical experiment, the 343 nm output of the laser beam is used to excite the microscope tip to generate pulsed electrons for probing, and the 515 nm output is used as a clocking excitation pulse to initiate dynamics. Time-resolved images demonstrate clearly that carrier recombination is significantly slowed after ODT treatment, which supports the efficient removal of surface trap states.
Collapse
|
88
|
Khan JI, Adhikari A, Sun J, Priante D, Bose R, Shaheen BS, Ng TK, Zhao C, Bakr OM, Ooi BS, Mohammed OF. Enhanced Optoelectronic Performance of a Passivated Nanowire-Based Device: Key Information from Real-Space Imaging Using 4D Electron Microscopy. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2016; 12:2313-2320. [PMID: 26938476 DOI: 10.1002/smll.201503651] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/02/2015] [Revised: 02/03/2016] [Indexed: 06/05/2023]
Abstract
Managing trap states and understanding their role in ultrafast charge-carrier dynamics, particularly at surface and interfaces, remains a major bottleneck preventing further advancements and commercial exploitation of nanowire (NW)-based devices. A key challenge is to selectively map such ultrafast dynamical processes on the surfaces of NWs, a capability so far out of reach of time-resolved laser techniques. Selective mapping of surface dynamics in real space and time can only be achieved by applying four-dimensional scanning ultrafast electron microscopy (4D S-UEM). Charge carrier dynamics are spatially and temporally visualized on the surface of InGaN NW arrays before and after surface passivation with octadecylthiol (ODT). The time-resolved secondary electron images clearly demonstrate that carrier recombination on the NW surface is significantly slowed down after ODT treatment. This observation is fully supported by enhancement of the performance of the light emitting device. Direct observation of surface dynamics provides a profound understanding of the photophysical mechanisms on materials' surfaces and enables the formulation of effective surface trap state management strategies for the next generation of high-performance NW-based optoelectronic devices.
Collapse
|
89
|
Ahmad AL, Ideris N, Ooi BS, Low SC, Ismail A. Optimization of polyvinylidene fluoride (PVDF) membrane fabrication for protein binding using statistical experimental design. J Immunoassay Immunochem 2016; 37:421-37. [PMID: 27088961 DOI: 10.1080/15321819.2016.1157489] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Statistical experimental design was employed to optimize the preparation conditions of polyvinylidenefluoride (PVDF) membranes. Three variables considered were polymer concentration, dissolving temperature, and casting thickness, whereby the response variable was membrane-protein binding. The optimum preparation for the PVDF membrane was a polymer concentration of 16.55 wt%, a dissolving temperature of 27.5°C, and a casting thickness of 450 µm. The statistical model exhibits a deviation between the predicted and actual responses of less than 5%. Further characterization of the formed PVDF membrane showed that the morphology of the membrane was in line with the membrane-protein binding performance.
Collapse
|
90
|
Zhao C, Ng TK, Wei N, Prabaswara A, Alias MS, Janjua B, Shen C, Ooi BS. Facile Formation of High-Quality InGaN/GaN Quantum-Disks-in-Nanowires on Bulk-Metal Substrates for High-Power Light-Emitters. NANO LETTERS 2016; 16:1056-1063. [PMID: 26745217 DOI: 10.1021/acs.nanolett.5b04190] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
High-quality nitride materials grown on scalable and low-cost metallic substrates are considerably attractive for high-power light-emitters. We demonstrate here, for the first time, the high-power red (705 nm) InGaN/GaN quantum-disks (Qdisks)-in-nanowire light-emitting diodes (LEDs) self-assembled directly on metal-substrates. The LEDs exhibited a low turn-on voltage of ∼2 V without efficiency droop up to injection current of 500 mA (1.6 kA/cm(2)) at ∼5 V. This is achieved through the direct growth and optimization of high-quality nanowires on titanium (Ti) coated bulk polycrystalline-molybdenum (Mo) substrates. We performed extensive studies on the growth mechanisms, obtained high-crystal-quality nanowires, and confirmed the epitaxial relationship between the cubic titanium nitride (TiN) transition layer and the hexagonal nanowires. The growth of nanowires on all-metal stack of TiN/Ti/Mo enables simultaneous implementation of n-metal contact, reflector, and heat sink, which greatly simplifies the fabrication process of high-power light-emitters. Our work ushers in a practical platform for high-power nanowires light-emitters, providing versatile solutions for multiple cross-disciplinary applications that are greatly enhanced by leveraging on the chemical stability of nitride materials, large specific surface of nanowires, chemical lift-off ready layer structures, and reusable Mo substrates.
Collapse
|
91
|
Alias MS, Yang Y, Ng TK, Dursun I, Shi D, Saidaminov MI, Priante D, Bakr OM, Ooi BS. Enhanced Etching, Surface Damage Recovery, and Submicron Patterning of Hybrid Perovskites using a Chemically Gas-Assisted Focused-Ion Beam for Subwavelength Grating Photonic Applications. J Phys Chem Lett 2016; 7:137-142. [PMID: 26688008 DOI: 10.1021/acs.jpclett.5b02558] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
The high optical gain and absorption of organic-inorganic hybrid perovskites have attracted attention for photonic device applications. However, owing to the sensitivity of organic moieties to solvents and temperature, device processing is challenging, particularly for patterning. Here, we report the direct patterning of perovskites using chemically gas-assisted focused-ion beam (GAFIB) etching with XeF2 and I2 precursors. We demonstrate etching enhancement in addition to controllability and marginal surface damage compared to focused-ion beam (FIB) etching without precursors. Utilizing the GAFIB etching, we fabricated a uniform and periodic submicron perovskite subwavelength grating (SWG) absorber with broadband absorption and nanoscale precision. Our results demonstrate the use of FIB as a submicron patterning tool and a means of providing surface treatment (after FIB patterning to minimize optical loss) for perovskite photonic nanostructures. The SWG absorber can be patterned on perovskite solar cells to enhance the device efficiency through increasing light trapping and absorption.
Collapse
|
92
|
Retamal JRD, Oubei HM, Janjua B, Chi YC, Wang HY, Tsai CT, Ng TK, Hsieh DH, Kuo HC, Alouini MS, He JH, Lin GR, Ooi BS. 4-Gbit/s visible light communication link based on 16-QAM OFDM transmission over remote phosphor-film converted white light by using blue laser diode. OPTICS EXPRESS 2015; 23:33656-33666. [PMID: 26832029 DOI: 10.1364/oe.23.033656] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Visible Light Communication (VLC) as a new technology for ultrahigh-speed communication is still limited when using slow modulation light-emitting diode (LED). Alternatively, we present a 4-Gbit/s VLC system using coherent blue-laser diode (LD) via 16-quadrature amplitude modulation orthogonal frequency division multiplexing. By changing the composition and the optical-configuration of a remote phosphor-film the generated white light is tuned from cool day to neutral, and the bit error rate is optimized from 1.9 × 10(-2) to 2.8 × 10(-5) in a blue filter-free link due to enhanced blue light transmission in forward direction. Briefly, blue-LD is an alternative to LED for generating white light and boosting the data rate of VLC.
Collapse
|
93
|
Pan J, Sarmah SP, Murali B, Dursun I, Peng W, Parida MR, Liu J, Sinatra L, Alyami N, Zhao C, Alarousu E, Ng TK, Ooi BS, Bakr OM, Mohammed OF. Air-Stable Surface-Passivated Perovskite Quantum Dots for Ultra-Robust, Single- and Two-Photon-Induced Amplified Spontaneous Emission. J Phys Chem Lett 2015; 6:5027-33. [PMID: 26624490 DOI: 10.1021/acs.jpclett.5b02460] [Citation(s) in RCA: 206] [Impact Index Per Article: 22.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
We demonstrate ultra-air- and photostable CsPbBr3 quantum dots (QDs) by using an inorganic-organic hybrid ion pair as the capping ligand. This passivation approach to perovskite QDs yields high photoluminescence quantum yield with unprecedented operational stability in ambient conditions (60 ± 5% lab humidity) and high pump fluences, thus overcoming one of the greatest challenges impeding the development of perovskite-based applications. Due to the robustness of passivated perovskite QDs, we were able to induce ultrastable amplified spontaneous emission (ASE) in solution processed QD films not only through one photon but also through two-photon absorption processes. The latter has not been observed before in the family of perovskite materials. More importantly, passivated perovskite QD films showed remarkable photostability under continuous pulsed laser excitation in ambient conditions for at least 34 h (corresponds to 1.2 × 10(8) laser shots), substantially exceeding the stability of other colloidal QD systems in which ASE has been observed.
Collapse
|
94
|
Lee C, Shen C, Oubei HM, Cantore M, Janjua B, Ng TK, Farrell RM, El-Desouki MM, Speck JS, Nakamura S, Ooi BS, DenBaars SP. 2 Gbit/s data transmission from an unfiltered laser-based phosphor-converted white lighting communication system. OPTICS EXPRESS 2015; 23:29779-29787. [PMID: 26698461 DOI: 10.1364/oe.23.029779] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
We demonstrate data transmission of unfiltered white light generated by direct modulation of a blue gallium nitride (GaN) laser diode (LD) exciting YAG:Ce phosphors. 1.1 GHz of modulation bandwidth was measured without a limitation from the slow 3.8 MHz phosphor response. A high data transmission rate of 2 Gbit/s was achieved without an optical blue-filter using a non-return-to-zero on-off keying (NRZ-OOK) modulation scheme. The measured bit error rate (BER) of 3.50 × 10(-3) was less than the forward error correction (FEC) limit of 3.8 × 10(-3). The generated white light exhibits CIE 1931 chromaticity coordinates of (0.3628, 0.4310) with a color rendering index (CRI) of 58 and a correlated color temperature (CCT) of 4740 K when the LD was operated at 300 mA. The demonstrated laser-based lighting system can be used simultaneously for indoor broadband access and illumination applications with good color stability.
Collapse
|
95
|
Zhao C, Ng TK, Prabaswara A, Conroy M, Jahangir S, Frost T, O'Connell J, Holmes JD, Parbrook PJ, Bhattacharya P, Ooi BS. An enhanced surface passivation effect in InGaN/GaN disk-in-nanowire light emitting diodes for mitigating Shockley-Read-Hall recombination. NANOSCALE 2015; 7:16658-16665. [PMID: 26242178 DOI: 10.1039/c5nr03448e] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
We present a detailed study of the effects of dangling bond passivation and the comparison of different sulfide passivation processes on the properties of InGaN/GaN quantum-disk (Qdisk)-in-nanowire based light emitting diodes (NW-LEDs). Our results demonstrated the first organic sulfide passivation process for nitride nanowires (NWs). The results from Raman spectroscopy, photoluminescence (PL) measurements, and X-ray photoelectron spectroscopy (XPS) showed that octadecylthiol (ODT) effectively passivated the surface states, and altered the surface dynamic charge, and thereby recovered the band-edge emission. The effectiveness of the process with passivation duration was also studied. Moreover, we also compared the electro-optical performance of NW-LEDs emitting at green wavelength before and after ODT passivation. We have shown that the Shockley-Read-Hall (SRH) non-radiative recombination of NW-LEDs can be greatly reduced after passivation by ODT, which led to a much faster increasing trend of quantum efficiency and higher peak efficiency. Our results highlighted the possibility of employing this technique to further design and produce high performance NW-LEDs and NW-lasers.
Collapse
|
96
|
Oubei HM, Duran JR, Janjua B, Wang HY, Tsai CT, Chi YC, Ng TK, Kuo HC, He JH, Alouini MS, Lin GR, Ooi BS. 4.8 Gbit/s 16-QAM-OFDM transmission based on compact 450-nm laser for underwater wireless optical communication. OPTICS EXPRESS 2015; 23:23302-9. [PMID: 26368431 DOI: 10.1364/oe.23.023302] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
We experimentally demonstrate an underwater wireless optical communications (UWOC) employing 450-nm TO-9 packaged and fiber-pigtailed laser diode (LD) directly encoded with an orthogonal frequency division multiplexed quadrature amplitude modulation (QAM-OFDM) data. A record data rate of up to 4.8 Gbit/s over 5.4-m transmission distance is achieved. By encoding the full 1.2-GHz bandwidth of the 450-nm LD with a 16-QAM-OFDM data, an error vector magnitude (EVM) of 16.5%, a signal-to-noise ratio (SNR) of 15.63 dB and a bit error rate (BER) of 2.6 × 10(-3), well pass the forward error correction (FEC) criterion, were obtained.
Collapse
|
97
|
Oubei HM, Li C, Park KH, Ng TK, Alouini MS, Ooi BS. 2.3 Gbit/s underwater wireless optical communications using directly modulated 520 nm laser diode. OPTICS EXPRESS 2015; 23:20743-20748. [PMID: 26367926 DOI: 10.1364/oe.23.020743] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
We experimentally demonstrate a record high-speed underwater wireless optical communication (UWOC) over 7 m distance using on-off keying non-return-to-zero (OOK-NRZ) modulation scheme. The communication link uses a commercial TO-9 packaged pigtailed 520 nm laser diode (LD) with 1.2 GHz bandwidth as the optical transmitter and an avalanche photodiode (APD) module as the receiver. At 2.3 Gbit/s transmission, the measured bit error rate of the received data is 2.23×10(-4), well below the forward error correction (FEC) threshold of 2×10(-3) required for error-free operation. The high bandwidth of the LD coupled with high sensitivity APD and optimized operating conditions is the key enabling factor in obtaining high bit rate transmission in our proposed system. To the best of our knowledge, this result presents the highest data rate ever achieved in UWOC systems thus far.
Collapse
|
98
|
Janjua B, Oubei HM, Durán Retamal JR, Ng TK, Tsai CT, Wang HY, Chi YC, Kuo HC, Lin GR, He JH, Ooi BS. Going beyond 4 Gbps data rate by employing RGB laser diodes for visible light communication. OPTICS EXPRESS 2015; 23:18746-18753. [PMID: 26191934 DOI: 10.1364/oe.23.018746] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
With increasing interest in visible light communication, the laser diode (LD) provides an attractive alternative, with higher efficiency, shorter linewidth and larger bandwidth for high-speed visible light communication (VLC). Previously, more than 3 Gbps data rate was demonstrated using LED. By using LDs and spectral-efficient orthogonal frequency division multiplexing encoding scheme, significantly higher data rates has been achieved in this work. Using 16-QAM modulation scheme, in conjunction with red, blue and green LDs, data rates of 4.4 Gbps, 4 Gbps and 4 Gbps, with the corresponding BER/SNR/EVM of 3.3 × 10⁻³/15.3/17.9, 1.4 × 10⁻³/16.3/15.4 and 2.8 × 10⁻³/15.5/16.7were obtained over transmission distance of ~20 cm. We also simultaneously demonstrated white light emission using red, blue and green LDs, after passing through a commercially available diffuser element. Our work highlighted that a tradeoff exists in operating the blue LDs at optimum bias condition while maintaining good color temperature. The best results were obtained when encoding red LDs which gave both the strongest received signal amplitude and white light with CCT value of 5835K.
Collapse
|
99
|
Shen C, Ng TK, Ooi BS. Enabling area-selective potential-energy engineering in InGaN/GaN quantum wells by post-growth intermixing. OPTICS EXPRESS 2015; 23:7991-7998. [PMID: 25837136 DOI: 10.1364/oe.23.007991] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
We report on a unique area-selective, post-growth approach in engineering the quantum-confined potential-energy profile of InGaN/GaN quantum wells (QWs) utilizing metal/dielectric-coating induced intermixing process. This led to simultaneous realization of adjacent regions with peak emission of 2.74 eV and 2.82 eV with a high spatial resolution (~1 μm) at the coating boundary. The potential profile softening in the intermixed QW light-emitting diode (LED) was experimentally and numerically correlated, shedding light on the origin of alleviated efficiency droop from 30.5% to 16.6% (at 150 A/cm²). The technique is advantageous for fabricating high efficiency light-emitters, and is amenable to monolithic integration of nitride-based photonic devices.
Collapse
|
100
|
Frost T, Jahangir S, Stark E, Deshpande S, Hazari A, Zhao C, Ooi BS, Bhattacharya P. Monolithic electrically injected nanowire array edge-emitting laser on (001) silicon. NANO LETTERS 2014; 14:4535-4541. [PMID: 24971807 DOI: 10.1021/nl5015603] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
A silicon-based laser, preferably electrically pumped, has long been a scientific and engineering goal. We demonstrate here, for the first time, an edge-emitting InGaN/GaN disk-in-nanowire array electrically pumped laser emitting in the green (λ = 533 nm) on (001) silicon substrate. The devices display excellent dc and dynamic characteristics with values of threshold current density, differential gain, T0 and small signal modulation bandwidth equal to 1.76 kA/cm(2), 3 × 10(-17) cm(2), 232 K, and 5.8 GHz respectively under continuous wave operation. Preliminary reliability measurements indicate a lifetime of 7000 h. The emission wavelength can be tuned by varying the alloy composition in the quantum disks. The monolithic nanowire laser on (001)Si can therefore address wide-ranging applications such as solid state lighting, displays, plastic fiber communication, medical diagnostics, and silicon photonics.
Collapse
|