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Synthesis of Plasmonic Photocatalysts for Water Splitting
摘要： Production of H2, O2, and some useful chemicals by solar water splitting is widely expected to be one of the ultimate technologies in solving energy and environmental problems worldwide. Plasmonic enhancement of photocatalytic water splitting is attracting much attention. However, the enhancement factors reported so far are not as high as expected. Hence, further investigation of the plasmonic photocatalysts for water splitting is now needed. In this paper, recent work demonstrating plasmonic photocatalytic water splitting is reviewed. Particular emphasis is given to the fabrication process and the morphological features of the plasmonic photocatalysts.
关键词： metal nanostructure,solar water splitting,surface plasmon resonance,semiconductor,metal nanoparticle
更新于2025-09-11 14:15:04
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InAs/GaAs Quantum Dot Dual-Mode Distributed Feedback Laser Towards Large Tuning Range Continuous-Wave Terahertz Application
摘要： In this paper, a laterally coupled distributed feedback (LC-DFB) laser based on modulation p-doped multiple InAs/GaAs quantum dot (QD) structures has been fabricated. The device exhibits a high side-mode suppression ratio (SMSR) of > 47 dB and a high thermal stability of dλ/dT = 0.092 nm/K under continuous-wave (CW) operation, which is mainly attributed to the high material gain prepared by modulation p-doping and rapid thermal annealing (RTA) process, and the significantly reduced waveguide losses by shallow-etched gratings and its close proximity to the laser ridge feature in the LC-DFB laser. With this superior performance of the DFB laser, the wide tunable dual-wavelength lasing operation has been obtained by delicately defining different periods for the grating structures on the two sides of the laser ridge or combining the reduced laser cavity length. The wavelength spacing between the two lasing modes can be flexibly tuned in a very wide range from 0.5 to 73.4 nm, corresponding to the frequency difference from 0.10 to 14 THz, which is the largest tuning range by the utilization of single device and hence providing a new opportunity towards the generation of CW THz radiation.
关键词： Semiconductor lasers,Lasers,Distributed feedback,Optoelectronics,Terahertz imaging,Quantum well, wire, and dot devices
更新于2025-09-11 14:15:04
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Comparative study of photoluminescence for type-I InAs/GaAs0.89Sb0.11 and type-II InAs/GaAs0.85Sb0.15 quantum dots
摘要： InAs quantum dots (QDs) sandwiched inside a GaAsSb matrix possess advantages for achieving telecom wavelength lasers and for developing high efficiency solar cells. In this work, optical properties of InAs quantum dots (QDs) capped by GaAs1-xSbx (x ? 0.11 and 0.15) are comparatively investigated. The photoluminescence measurements reflect that the energy state filling, thermal activation, quenching, and lifetime of the carriers in InAs/GaAs0.89Sb0.11 QDs are different from those in the InAs/GaAs0.85Sb0.15 QDs. These differences are attributed to the band alignment transition from type-I to type-II resulting from the Sb-composition change from x ? 0.11 to x ? 0.15 in the GaAs1-xSbx capping layer. Therefore, the emission and quenching involve excited states for type-I InAs/GaAs0.85Sb0.15 QDs, but involve InAs QDs as well as the GaAs0.85Sb0.15 QW recombination for type-II InAs/GaAs0.85Sb0.15 QDs. So the luminescence reveals complex and distinct physics mechanisms for these two samples.
关键词： Photoluminescence,Quantum dots,Band alignment,Semiconductor compound
更新于2025-09-11 14:15:04
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Electronically Tunable Distributed Feedback (DFB) Laser on Silicon
摘要： An electronically tunable distributed feedback (DFB) laser heterogeneously integrated on a silicon photonics platform is experimentally demonstrated. Tuning is achieved through carrier injection into the tuning layer of a tunable twin-guide III–V membrane on silicon. A 2 nm continuous tuning range is achieved with a single tuning current. Continuous-wave single-mode laser operation with a side-mode suppression ratio larger than 44 dB across the tuning range is obtained. Measured wavelength switching times are on the order of 3 ns and non-return-to-zero on-o? keying direct modulation at 12.5 Gbit s?1 is readily achieved. This work can be a major advance toward the realization of optical burst or packet switching systems for future data center networks.
关键词： silicon photonics,electronic wavelength tuning,distributed feedback lasers,semiconductor lasers
更新于2025-09-11 14:15:04
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Impact of a topological defect and Rashba spin-orbit interaction on the thermo-magnetic and optical properties of a 2D semiconductor quantum dot with Gaussian confinement
摘要： In this paper, we examine the effect of introducing a conical disclination on the thermal and optical properties of a two dimensional GaAs quantum dot in the presence of a uniform and constant magnetic field. In particular, our model consists of a single-electron subject to a confining Gaussian potential with a spin-orbit interaction in the Rashba approach. We compute the specific heat and the magnetic susceptibility from the exact solution of the Schr?dinger equation via the canonical partition function, and it is shown that the peak structure of the Schottky anomaly is linearly displaced as a function of the topological defect. We found that such defect and the Rashba coupling modify the values of the temperature and magnetic field in which the system behaves as a paramagnetic material. Remarkably, the introduction of a conical disclination in the quantum dot relaxes the selection rules for the electronic transitions when an external electromagnetic field is applied. This creates a new set of allowed transitions causing the emergence of semi-suppressed resonances in the absorption coefficient as well as in the refractive index changes which are blue-shifted with respect to the regular transitions for a quantum dot without the defect.
关键词： Rashba spin-orbit interaction,optical properties,thermo-magnetic properties,topological defect,2D semiconductor quantum dot,Gaussian confinement
更新于2025-09-11 14:15:04
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Ultranarrow-waveguide AlGaAs/GaAs/InGaAs lasers
摘要： We have designed, fabricated and studied ultranarrow-waveguide heterostructure lasers emitting in the spectral range 1000 – 1100 nm. The lasers have been characterised by current – voltage, light – current, far-field intensity distribution and internal optical loss measurements. The ultranarrow-waveguide lasers have been shown to have a threshold current density of ~75 A cm–2, internal quantum efficiency near 100 % and internal optical loss near the lasing threshold under 1 cm–1, which corresponds to the level of standard heterostructures. We have demonstrated the possibility of obtaining up to 5 W of output power in continuous mode and up to 30 W in pulsed mode, with a beam convergence (FWHM) of 17.8°. The slope of the internal optical loss as a function of pump current for the ultranarrow-waveguide lasers can be markedly lower than that in lasers with a standard design, but internal quantum efficiency drops to 40 % with increasing pump current. The use of barrier layers in ultranarrow-waveguide lasers makes it possible to substantially reduce the drop in internal quantum efficiency.
关键词： absorption coefficient,internal optical loss,ultranarrow waveguide,energy barrier,pulsed pumping,semiconductor laser
更新于2025-09-11 14:15:04
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Embedded quantum dots in semiconductor nanostructures
摘要： In this work, we report the behavior of the tunneling current in a semiconductor nanostructure of (Ga, Al)As/GaAs which takes into account the behavior of the electrons and the Rashba’s spin orbit interaction in the presence of embedded quantum dots of di?erent geometries (lens, pyramid and ring) in voltage function, magnetic ?eld, and the di?erent values of the interaction spin orbit (π/2, π/4 and 3π/4). The results that were obtained show, that the intensity of the current presents appreciable changes when is changed the con?guration of the quantum dot as the intensities of external ?elds and spin polarization as well. All these internal and external e?ects that are studied in our model, signi?cantly modify the transport of information of the semiconductor nanostructure, our results show that the spin e?ects and the quantum dot con?guration contribute to the quantum memories e?ciency and the spin ?lter devices of actual use on nanoscience and nanotechnology.
关键词： quantum dots,Rashba’s spin orbit interaction,tunneling current,semiconductor nanostructures
更新于2025-09-11 14:15:04
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[IEEE 2019 IEEE Photonics Conference (IPC) - San Antonio, TX, USA (2019.9.29-2019.10.3)] 2019 IEEE Photonics Conference (IPC) - An Investigation on 25Gb/s Ultra-Short Cavity Quantum Well Lasers Operated at Elevated Temperatures
摘要： A Fabry-Perot quantum well laser with ultra-short cavity is designed and fabricated. The emission wavelength is at 1310nm band which is important for data center applications. The shortest cavity length is 25?m, and the laser has mW-class output with low threshold currents (4mA in average). At room temperature, an opened eye diagram with 28Gb/s transmission rate can be observed. Clear 25Gb/s eye patterns from 15oC to 65oC are also demonstrated.
关键词： Modulation,Fabry-Perot,Semiconductor lasers,Multiple quantum well,Diode lasers
更新于2025-09-11 14:15:04
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[IEEE 2019 IEEE Photonics Conference (IPC) - San Antonio, TX, USA (2019.9.29-2019.10.3)] 2019 IEEE Photonics Conference (IPC) - Edge Breakdown Suppression of Avalanche Photodiodes using Zn Diffusion and Selective Area Growth
摘要： Avalanche photodiodes are fabricated and characterized, using a single diffusion fabrication process with the surface patterned by selective area growth prior to diffusion. Raster mapping of the photocurrent near the breakdown voltage is used to characterize the electric field distribution in the multiplication layer. Devices fabricated with the precursor CBrCl3 introduced during selective area epitaxy show a smoother surface morphology and effective edge breakdown suppression, while those fabricated without CBrCl3 have a rougher surface morphology and exhibit evidence of premature edge breakdown at the corners of the device along specific crystal orientations. Comparison of the dark current – voltage curves below breakdown shows a reduction of dark current associated with the use of CBrCl3, as well as with the inclusion of floating guard rings in the device design.
关键词： Diffusion,Materials preparation,Optoelectronic and Photonic sensors,Doping,Semiconductor detectors
更新于2025-09-11 14:15:04
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MODELLING AND SIMULATION OF P-I-N QUANTUM DOT SEMICONDUCTOR SATURABLE ABSORBER MIRRORS
摘要： Semiconductor saturable absorber mirror (SESAM) based on InAs quantum dot (QD) is important in designing fast mode-locked laser devices. A self-consistent time-domain material travelling-wave (TDTW) model for the simulation of self-assembled QD-SESAM is developed. The 1-D TDTW model takes into consideration the time-varying QD optical susceptibility, refractive index variation resulting from the intersubband free-carrier absorption, homogeneous and inhomogeneous broadening. The carrier concentration rate equations are considered simultaneously with the travelling wave model. The model is used to analyze the characteristics of 1.3-μm p-i-n QD InAs-GaAs SESAM. The ?eld distribution resulting from the TDTW equations, in both the SESAM absorbing region and the distributed Bragg re?ectors, is obtained and used in ?nding the device characteristics including the modulation depth and recovery dynamics. These characteristics are studied considering the e?ects of QD surface density, inhomogeneous broadening, the number of QD absorbing layers, and the applied reverse voltage. The obtained results, based on the assumed device parameters, are in good agreement, qualitatively, with the experimental results.
关键词： Travelling-wave model,Quantum dot,Modulation depth,Semiconductor saturable absorber mirror,Recovery dynamics
更新于2025-09-11 14:15:04