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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - 25 GHz Small-Signal Modulation Bandwidth with a 7-Element Electrically-Parallel Vertical-Cavity Surface-Emitting Laser Array
摘要： Small arrays of VCSELs have emerging applications in free-space optical communications for a plethora of gadgets from smartphones to appliances to sensing systems within the realm of the Internet-of-Things. For data communication we require eye-safe line-of-sight beams or cones of light radiation that can reliably and inexpensively send data (as across optical fiber) from device-to-device or serve as an illumination source or both. Via our simplified VCSEL epitaxial designs [1] we investigate various configurations of top-emitting single 980 nm VCSELs and VCSEL arrays with varying VCSEL-to-VCSEL spacing, mesa shapes, and emitting diameters. We report record combinations of small-signal modulation bandwidth (f3dB) and optical output power (L) for an electrically-parallel compact VCSEL array with 7 VCSELs in a hexagonal configuration. The VCSELs in the array are identical with oxide aperture diameters estimated to be ? ~3.5 (cid:80)m ± 0.5 (cid:80)m. We summarize key room temperature (RT) performance figures-of-merit in Fig. 1. We achieve an f3dB of 20 GHz at a bias of about I ~35 mA with an operating L exceeding 25 mW. The f3dB is as high as 24.8 GHz with L ~50 mW when I ~65 mA. The maximum wall plug efficiency (WPE) is 0.32 at I ~16 mA. We anticipate increased WPE and optical output power for a given I with heat sinking, advanced packaging, and substrate-emitting array designs. Previous best array results include an f3dB of 7.5 GHz at L = 120 mW for a 28-element 850 nm array [2] and an f3dB of 23 GHz at L = 25 mW for a single 980 nm VCSEL. In our presentation we include additional experimental results on our large ? single VCSELs and on our triple, septuple, and novemdecuple VCSEL arrays from RT to 85 °C.
关键词： optical output power,VCSEL,electrically-parallel,small-signal modulation bandwidth,hexagonal configuration
更新于2025-09-12 10:27:22
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Rare Earth Doped Optical Fibers with Multi-section Core
摘要： The gain bandwidth of a single-mode fiber is limited by the atomic transitions of one rare earth gain element. Here we overcome this long-standing challenge by designing a new single-mode fiber with multi-section core, where each section is doped with different gain element. We theoretically propose and experimentally demonstrate that this configuration provides a gain bandwidth well beyond the capability of conventional design, whereas the inclusion of multiple sections does not compromise single-mode operation or the quality of the transverse modal profile. This new fiber will be beneficial in realizing all fiber laser systems with few-cycle pulse duration or octave tunability.
关键词： Rare Earth Doped Optical Fibers,Gain Bandwidth,Fiber Laser Systems,Single-mode Fiber,Multi-section Core
更新于2025-09-12 10:27:22
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[IEEE 2018 Asia Communications and Photonics Conference (ACP) - Hangzhou (2018.10.26-2018.10.29)] 2018 Asia Communications and Photonics Conference (ACP) - Energy Optimization with Passive WDM Based Fronthaul in Heterogeneous Cellular Networking
摘要： We propose a passive wavelength division multiplexing based fronthaul architecture for heterogeneous cellular networking, and a threshold based on/off algorithm for micro cells. Simulation results show that our algorithm significantly saves energy than traditional solutions.
关键词： fronthaul bandwidth,energy consumption,wavelength division multiplexing (WDM),switch on/off
更新于2025-09-12 10:27:22
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SDN-Enabled Sliceable Transceivers in Disaggregated Optical Networks
摘要： We programmable (SDN-enabled) sliceable bandwidth/bitrate variable transceivers (S-BVTs) based on multicarrier modulation (MCM) with direct detection (DD), tailored for disaggregated metro networks. A first level of disaggregation is assessed by considering an S-BVT architecture composed of a set of white box bandwidth/bit rate variable transceivers (BVTs) from multiple manufacturers/providers. An OpenConfig vendor-neutral model is adopted for the implementation of the SDN agents that configure the S-BVTs according to the network requirements/targets. Additionally, a fully disaggregated metro network is envisioned by considering a fixed/flexi-grid dense wavelength division multiplexing (DWDM) network with white box ROADM/OXC nodes. The impact of the filter narrowing effect is assessed considering different network node architectures based on either flexible wavelength selective switches (WSSes) or arrayed waveguide gratings (AWGs). Thanks to the transceiver inherent modularity, flexibility and bit rate variability, up to 8 network nodes can be traversed ensuring a target capacity of 50 Gb/s per slice at a 4.62 · 10?3 BER.
关键词： optical metro networks,software defined networking (SDN),sliceable bandwidth/bitrate variable transceiver (S-BVT),Disaggregation,filter narrowing effect,wavelength selective switch (WSS)
更新于2025-09-12 10:27:22
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[IEEE TENCON 2019 - 2019 IEEE Region 10 Conference (TENCON) - Kochi, India (2019.10.17-2019.10.20)] TENCON 2019 - 2019 IEEE Region 10 Conference (TENCON) - Bandwidth Enhancement of Aperture Coupled Cylindrical Dielectric Resonator Antenna using Modified Feed Structure
摘要： A compact rectangular shaped aperture coupled cylindrical dielectric resonator antenna achieving bandwidth improvement using a modified feed is presented. The antenna contributes a 10 dB impedance bandwidth that ranges from 8.21 GHz to 13.07 GHz. The proposed antenna offers stable broadside radiation pattern which can be effectively used in X band for radar, satellite communication, and wireless computer networks.
关键词： X band,Aperture coupling,Dielectric resonator antenna,Bandwidth,Microstrip feed
更新于2025-09-12 10:27:22
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[IEEE 2019 IEEE 90th Vehicular Technology Conference (VTC2019-Fall) - Honolulu, HI, USA (2019.9.22-2019.9.25)] 2019 IEEE 90th Vehicular Technology Conference (VTC2019-Fall) - Parasitic Slot Elements for Bandwidth Enhancement of Slotted Waveguide Antennas
摘要： The use of extra slots in a slotted waveguide array for improving the impedance bandwidth is investigated. This has not widely studied previously, probably because the directive pattern is a primary parameter for the waveguide array and extra elements are prone to spoiling the control of the pattern. However, the pattern is not a primary design parameter for most mobile terminals, and here we seek a wide bandwidth for a smaller antenna than the traditional waveguide array, which is suitable for a mobile terminal. The extra slots can be viewed as parasitic elements, analogously to free-space thin wire parasitic, but the designs are not interchangeable with wire antennas. This is because the waveguide - both the internal and external structure - constrains the excitation of the slot elements in a different way to that of the wire antenna analogies. Simple-to-build designs are sought where the slot elements are on only one of the waveguide broad walls. The approach is experimental (simulation) which allows rapid and accurate evaluation of different con?gurations. We do not optimize a con?guration because any optimal design will depend on the speci?c structure of the mobile terminal supporting the antenna. For the basic stand-alone waveguide, a -6dB impedance bandwidth of ～ 30% is demonstrated using four slot elements in a short waveguide.
关键词： wide bandwidth,Parasitic slot element,slotted waveguide antenna
更新于2025-09-12 10:27:22
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Photodetectors [Working Title] || Overcoming the Bandwidth-Quantum Efficiency Trade-Off in Conventional Photodetectors
摘要： Optical systems and microwave photonics applications rely heavily on high-performance photodetectors having a high bandwidth-efficiency product. The main types of photodetector structures include Schottky and PIN-photodiodes, heterojunction phototransistors, avalanche photodetectors, and metal-semiconductor-metal photodetectors. Vertically-illuminated photodetectors intrinsically present bandwidth-efficiency limitations, but these have been mitigated by new innovations over the years in quantum well photodetectors, edge-coupled photodetectors and resonant-cavity enhanced photodetectors for improved photophysical characteristics. Edge-coupled ultra-high-speed photodetectors have yielded high conversion efficiencies, and the active device structure of resonant-cavity-enhanced photodetectors allows wavelength selectivity and optical field enhancement due to resonance, enabling photodetectors to be made thinner and hence faster, while simultaneously increasing the quantum efficiency at the resonant wavelengths. Single-photon avalanche diodes have been developed, which combine an ultimate sensitivity with excellent timing accuracy. Further advances in addressing the bandwidth-quantum efficiency trade-off have incorporated photon-trapping nanostructures and plasmonic nanoparticles. Nanowire photodetectors have also demonstrated the highest photophysical performance to date.
关键词： photosensitivity,saturation current,quantum efficiency,optical absorption,drift layers,bandwidth-efficiency product
更新于2025-09-12 10:27:22
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Tellurene Photodetector with High Gain and Wide Bandwidth
摘要： Two-dimensional (2D) semiconductors have been extensively explored as a new class of materials with great potential. In particular, black phosphorus (BP) has been considered to be a strong candidate for applications such as high-performance infrared photodetectors. However, the scalability of BP thin film is still a challenge, and its poor stability in the air has hampered the progress of the commercialization of BP devices. Herein, we report the use of hydrothermal-synthesized and air-stable 2D tellurene nanoflakes for broadband and ultrasensitive photodetection. The tellurene nanoflakes show high hole mobilities up to 458 cm2/V·s at ambient conditions, and the tellurene photodetector presents peak extrinsic responsivity of 383 A/W, 19.2 mA/W, and 18.9 mA/W at 520 nm, 1.55 μm, and 3.39 μm light wavelength, respectively. Due to the photogating effect, high gains up to 1.9 ×103 and 3.15×104 are obtained at 520 nm and 3.39 μm wavelength, respectively. At the communication wavelength of 1.55μm, the tellurene photodetector exhibits an exceptionally high anisotropic behavior, and a large bandwidth of 37 MHz is obtained. The photodetection performance at different wavelength is further supported by the corresponding quantum molecular dynamics (QMD) simulations. Our approach has demonstrated the air-stable tellurene photodetectors that fully cover the short-wave infrared band with ultrafast photoresponse.
关键词： air-stable,two-dimensional (2D),wide bandwidth,tellurene,photodetector,high gain
更新于2025-09-12 10:27:22
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[IEEE 2019 International Conference on Numerical Simulation of Optoelectronic Devices (NUSOD) - Ottawa, ON, Canada (2019.7.8-2019.7.12)] 2019 International Conference on Numerical Simulation of Optoelectronic Devices (NUSOD) - Electrical Properties of Oxide-Confined Vertical-Cavity Surface-Emitting Lasers
摘要： We present a comprehensive description of electrical properties of vertical-cavity surface-emitting lasers (VCSELs) based on a drift-diffusion model applied to carrier transport in 3D multilayer semiconductor laser heterostructure with a p-n junction. We address the impact of interface grading in distributed Bragg reflectors (DBRs), modulation doping of the DBRs and surrounding layers of the quantum well (QW) as well as material-dependent carrier mobilities and recombination constants and are focused on oxide-confined GaAs/AlGaAs VCSELs. We evaluate both depletion and diffusion capacitance and show that both contributions to the capacitance as well as the differential series resistance critically depend on the injection current and chip design such that, in general, VCSEL cannot be properly modeled by an equivalent circuit approximation. Current profiles demonstrate significant increase of the current density at the edges of the oxide-confined aperture (current crowding) which could be suppressed by a proper design.
关键词： current crowding,differential resistance,oxide aperture,carrier transport,capacitance,modulation frequency bandwidth,vertical cavity surface-emitting laser
更新于2025-09-12 10:27:22
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Regimes of bandwidth enhancement in coupled-cavity semiconductor laser using photon–photon resonance
摘要： In the last decade, different solutions were proposed to boost the transmission bitrate of semiconductor lasers. Here, we focus on applying optical feedback to a semiconductor laser from an external cavity in order to induce enhancement of the modulation bandwidth up to 50 GHz as well as resonant modulation (RM) around frequencies approaching 60 GHz. High-speed modulation up to 90 Gbps under none-return to zero operation and a 45 Gbaud using pulse amplitude modulation-4 signals are predicted. Both types of improving the modulation performance of the laser are attributed to the photon–photon resonance (PPR) effect. The regimes of the external power reflectivity that correspond to both types of modulation response are specified. Comprehensive simulations are introduced to correlate the PPR frequency to the RM frequencies of the non-modulated coupled-cavity laser. Dependencies of the enhanced BW and PPR frequency on the cavity length and bias current are elucidated.
关键词： optical feedback,photon–photon resonance,modulation bandwidth,high-speed modulation,semiconductor lasers
更新于2025-09-11 14:15:04