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High resonance frequency in a coupled cavity DFB-LD with two phase-shifts
摘要： To realize a single-longitudinal-mode laser diode (LD) with high speed direct-modulation, a coupled cavity DFB-LD with two phase-shifts is proposed. From simulated results, it is expected that the resonance frequency of 71.3 GHz and the 3-dB down bandwidth of 95.9 GHz are obtained when the injected current is 3.075 times the threshold current. The resonance frequency for a main-mode is enhanced by an interaction between the main-mode and sub-mode. This interaction is called photon–photon resonance. The proposed coupled cavity DFB-LD is composed of two regions which are connected in series. Both regions have phase-shifted gratings. The phase-shift of the first region is ? π; the phase-shift of the second region is ? 0.9π. A phase-shift is not introduced at the interface of the two regions. The corrugation pitch of the second region is shorter than that of the first region by 1.6 nm; the grating coupling coefficient is 40 cm?1; each region length is 300 μm. These parameters are modest to fabricate DFB-LDs.
关键词： Longitudinal mode,Coupled cavity,Direct modulation,Semiconductor laser,Diffraction grating
更新于2025-09-23 15:19:57
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Impact of Chirp in High-Capacity Optical Metro Networks Employing Directly-Modulated VCSELs
摘要： Directly modulated long-wavelength vertical cavity surface emitting lasers (VCSELs) are considered for the implementation of sliceable bandwidth/bitrate variable transceivers for very high capacity transmission (higher than 50 Gb/s per wavelength) in metropolitan area systems characterized by reduced cost, power consumption, and footprint. The impact of the frequency chirp measured for InP VCSELs with different kinds of design (high-bandwidth very short cavity and widely-tunable with micro electro-mechanical systems (MEMS) top mirror) is analyzed in case of discrete multitone (DMT) direct modulation in combination with 25-GHz wavelength selective switch (WSS) filtering. The maximum transmitted capacity for both dual side- and single side-band DMT modulation is evaluated as a function of the number of crossed nodes in a mesh metro network, comparing VCSEL based transmitters performance also with the case of external electro-absorption modulator use. Finally, the maximum reach achieved based on the received optical signal to noise ratio (OSNR) and the fiber span length is discussed. The results confirm the possibility to use directly-modulated long-wavelength VCSELs for the realization of sliceable bandwidth/bitrate variable transmitters targeting 50-Gb/s capacity per polarization, also in the presence of 5 crossed WSSs for reaches of hundreds of kilometers in multi-span Erbium-doped fiber amplified (EDFA) metro links supported by coherent detection.
关键词： optical communications,vertical cavity surface emitting lasers,discrete multitone,metro networks,direct modulation
更新于2025-09-19 17:15:36
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High-speed directly-modulated cylindrical vector beam lasers
摘要： Cylindrical vector (CV) beams are highly desirable for wide applications ranging from manipulation to communications. Despite diverse schemes of CV beam emitters, the efficient generation of vector beams by active photonic integrated devices, especially for direct modulation, is still an outstanding challenge. Here, we report the first high-speed directly-modulated CV beam laser under electrical pumping. InP-based microring cavities with two sets of optimized second-order gratings enable single-mode lasing and efficient emission assisted by ion implantation. The high-differential-gain multiple-quantum-well structure and small active region benefit high-speed modulation. The surface emission facilitates easy 2D array integration. CV beam lasing is achieved with >1mW output power and ~50dB side-mode suppression-ratio (SMSR). CV beam lasers at 8-20Gbit/s are realized in the experiment. Moreover, a 2-km fiber vector eigenmode transmission link, seeded by a 10-Gbit/s directly-modulated CV beam laser, is also demonstrated with favorable performance. These may open a door to find more CV beam enabled classical and quantum communication applications employing integrated lasers.
关键词： photonic integrated devices,Cylindrical vector beam,microring resonator,direct modulation,semiconductor laser
更新于2025-09-16 10:30:52
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[IEEE 2019 18th International Conference on Optical Communications and Networks (ICOCN) - Huangshan, China (2019.8.5-2019.8.8)] 2019 18th International Conference on Optical Communications and Networks (ICOCN) - Analysis on Gain And Noise Figure of Direct Modulation RoF Link
摘要： The equivalent circuit model of direct modulation RoF link is introduced. Based on this model, the mathematical expressions of link gain and noise figure are both derived. The factors affecting the transmission characteristics, especially the parasitic parameters of lasers and detectors, are further analyzed. Finally, a general method to improve link gain and reduce noise figure is given.
关键词： gain,direct modulation,RoF,noise figure
更新于2025-09-16 10:30:52
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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) - Characteristics of Injection Microdisk Lasers with InGaAs/GaAs Quantum Well-Dots
摘要： Quantum dot (QD) based microdisk/microring lasers have attracted attention as promising candidates for on-chip optical interconnects since they offer small footprint, high-temperature stability and in-plane light emission. An important property required for a laser intended for optical communication is high-frequency direct modulation. Edge emitting QD-based lasers on GaAs demonstrated promising modulation characteristics with a -3 dB modulation bandwidth in excess of 7.4 GHz [1]. Meanwhile, there are practically no reports on the dynamic characteristics of QD-based microdisk/microring lasers. In the present work, we report on characteristics of microdisk lasers on GaAs substrates with diameters less than 30 μm. An ultra-dense (several 1011 cm-2) array of narrow-bandgap In-rich islands inside an In-depleted residual quantum well is used as the active region. These nanostructures are referred to as quantum well-dots (QWDs) [2] as their properties can be tuned from quantum well like to quantum dot like depending upon the composition and thickness of material deposited. Owing to a high density of the islands, a higher optical gain is achieved as compared to that of conventional In(Ga)As QDs, whereas the lateral carrier transport is suppressed as opposed to a quantum well. An epitaxial wafer was grown on an n+-GaAs(100)6o substrate by low pressure MOVPE using hydrogen as a carrier gas, arsine as a group V precursor, trimethylgallium, trimethylindium, and trimethylaluminum as group III precursors, silane and diethylzinc as n-type and p-type dopants. An Al0.34Ga0.66As/GaAs laser heterostructure comprises a 0.8 μm-thick GaAs separate confinement layer with 5 layers of QWDs formed by the deposition of 8 monolayers In0.4Ga0.6As and separated with 40 nm-thick GaAs spacers. Laser microresonators were formed by single-step photolithography and dry etching of 5.5 μm-high mesas with nearly vertical sidewalls. Ohmic contacts were formed with AgMn/NiAu and AuGe/Ni/Au metallizations upon the p+ GaAs cap layer and the n-doped GaAs substrate, respectively. The measurements were done at room temperature without external temperature stabilization and cooling. In a 30-μm diameter microdisk laser with InGaAs QWDs a high output power of 18 mW and a peak electrical-to-optical power conversion efficiency of 15 % were demonstrated. CW lasing was observed up to 110oC [3]. A maximum -3 dB modulation frequency of 5.9 GHz was found in the microdisk with a diameter less than 30 μm. To the best of our knowledge, these microlasers are the smallest QD microdisk/microring lasers, for which a direct modulation has been realized. Owing to a reduced cavity volume, a modulation current efficiency factor of 1.5 GHz/mA1/2 was estimated, and bias currents, at which the maximal modulation frequency is achieved is in the range of 30 mA (for comparison, MCEF of 0.38 GHz/mA1?2 and injected current of 86 mA was reported in [4]). The K-limited maximal frequency of 13 GHz was estimated from the modulation response analysis, whereas the experimentally measured –3 dB modulation frequency is 5.9 GHz. We suggest the bandwidth is limited by thermal effects or RC parasites, or a combination of those.
关键词： high-frequency direct modulation,microdisk lasers,optical interconnects,quantum well-dots,Quantum dot
更新于2025-09-12 10:27:22
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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) - VCSEL Technologies for High-Capacity Dense WDM Networks
摘要： Long-wavelength vertical cavity surface emitting laser (VCSEL) technologies can represent an alternative solution for the development of transmitters with reduced cost, power consumption and footprint for very-high capacity metropolitan area systems. Exploiting direct modulation (DM) and advanced modulation formats, such as discrete multitone (DMT), and aggregating multiple DM-VCSELs emitting in the C-band with dense wavelength division multiplexers (WDM) in SOI chips allows to achieve multi-Tb/s transmitter module with 25 GHz granularity [1]. The interplay between the frequency chirp induced by VCSELs DM and the tight filtering of network WDM multiplexers plays a crucial role in the transmission performance. In this paper, we compare the adoption of two different long-wavelength InP VCSEL technologies: high-bandwidth short-cavity devices and MEMS-based widely-tuneable VCSELs [1]. We evaluate their performance in case of DM employing DMT modulation, providing more than 50-Gb/s capacity per wavelength; coherent detection (COH-D) is used to target hundreds of kilometres distances thanks to DSP chromatic dispersion (CD) compensation.
关键词： WDM,DMT,direct modulation,coherent detection,VCSEL
更新于2025-09-11 14:15:04