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Quantum dot

Zhengwei Zhang, Jianqiu Chen, Yu Duan, Weixia Liu, Dan Li, Zhengyu Yan, Ke Yang
Here, we have presented a green and facile strategy to fabricate nitrogen-doped carbon dots (N-CDs) and their applications for determination of chlortetracycline (CTC) and sulfasalazine (SSZ). The fluorescent N-CDs, prepared by one-step hydrothermal reaction of citric acid and l-arginine, manifested numerous excellent features containing strong blue fluorescence, good water-solubility, narrow size distribution, and a high fluorescence quantum yield (QY) of 38.8%. Based on the fluorescence quenching effects, the as-synthesized N-CDs as a fluorescent nanosensor exhibited superior analytical performances for quantifying CTC and SSZ...
October 18, 2017: Luminescence: the Journal of Biological and Chemical Luminescence
Arpita Saha, Elena Oleshkevich, Clara Vinas, Francesc Teixidor
Closely packed hollow spheres connected through pillars to a CdSe quantum dot (QD) core produce channels through which ions navigate. This particular structure is well represented by [CdSe@CarbOPH(O)]@Cl/[N(Caprylyl)3 Me1 ] indicating that in the channels between the canopy made by the carboranyl spheres (carboranylphosphinate, CarbOPH(O)) and the CdSe core exist chloride anions. Due to the close packing, the spheres produce openings. These are converted into gates because [N(Caprylyl)3 Me1 ] acts as a plug...
October 17, 2017: Advanced Materials
Patrick Harvey-Collard, N Tobias Jacobson, Martin Rudolph, Jason Dominguez, Gregory A Ten Eyck, Joel R Wendt, Tammy Pluym, John King Gamble, Michael P Lilly, Michel Pioro-Ladrière, Malcolm S Carroll
Individual donors in silicon chips are used as quantum bits with extremely low error rates. However, physical realizations have been limited to one donor because their atomic size causes fabrication challenges. Quantum dot qubits, in contrast, are highly adjustable using electrical gate voltages. This adjustability could be leveraged to deterministically couple donors to quantum dots in arrays of qubits. In this work, we demonstrate the coherent interaction of a (31)P donor electron with the electron of a metal-oxide-semiconductor quantum dot...
October 18, 2017: Nature Communications
Som Sarang, Sara Bonabi Naghadeh, Binbin Luo, Parveen Kumar, Edwin Betady, Vincent Tung, Michael Scheibner, Jin Z Zhang, Sayantani Ghosh
Surface functionalization of nanoscale materials has a significant impact on their properties. We have demonstrated the effect of different passivating ligands on the crystal phase of organo-metal halide perovskite quantum dots (PQDs). Using static and dynamic spectroscopy, we studied phase transitions in CH3NH3PbBr3 PQDs ligated with either octylaminebromide (P-OABr) or 3-aminopropyl triethoxysilane (P-APTES). Around 140 K, P-OABr underwent a structural phase transition from tetragonal to orthorhombic, established by the emergence of a higher energy band in the photoluminescence (PL) spectrum...
October 18, 2017: Journal of Physical Chemistry Letters
Hyo-Min Kim, Jeonggi Kim, Sin-Young Cho, Jin Jang
We report the solution processed metal-oxide p-n junction, Li doped CuO (Li:CuO) and Li doped ZnO (Li:ZnO), as a charge generation junction (CGJ) in quantum-dot light-emitting diode (QLED) at reverse bias. Efficient charge generation is demonstrated in a stack of air annealed Li:CuO and Li:ZnO layers in QLEDs. Air annealing of Li:ZnO on Li:CuO turns out to be a key process to decrease the oxygen vacancy (Vo) and to increase the copper(II) oxide (CuO) fraction at the Li:CuO/Li:ZnO interface for efficient charge generation...
October 18, 2017: ACS Applied Materials & Interfaces
Mingyue Zhu, Qian Liu, Wei Chen, Yuanyuan Yin, Lan Ge, Henan Li, Kun Wang
The efficient separation of photogenerated electron-hole pairs in photoactive materials is highly desired, allowing their transfer to specific sites for undergoing redox reaction in various application. The construction of ternary heterojunctions is a practical strategy to enhance the migration of photogenerated electron that realizes the synergistic effect of multi-components rather than the simple overlay of single component. Here, we demonstrate an available way to fabricate new BiOCl/BiVO4/nitrogen-doped graphene quantum dots (N-GQDs) ternary heterojunctions that exhibit higher efficiency in charge separation than any binary heterojunctions or pure materials under visible light irradiation...
October 18, 2017: ACS Applied Materials & Interfaces
Thien Nguyen, Charles D Hill, Lloyd C L Hollenberg, Matthew R James
Solid-state spin-based qubits offer good prospects for scaling based on their long coherence times and nexus to large-scale electronic scale-up technologies. However, high-threshold quantum error correction requires a two-dimensional qubit array operating in parallel, posing significant challenges in fabrication and control. While architectures incorporating distributed quantum control meet this challenge head-on, most designs rely on individual control and readout of all qubits with high gate densities. We analysed the fan-out routing overhead of a dedicated control line architecture, basing the analysis on a generalised solid-state spin qubit platform parameterised to encompass Coulomb confined (e...
October 17, 2017: Scientific Reports
Yasutomo Ota, Masahiro Kakuda, Katsuyuki Watanabe, Satoshi Iwamoto, Yasuhiko Arakawa
Thresholdless lasing is an outstanding challenge in laser science and is achievable only in devices having near unity quantum efficiency even when not lasing. Such lasers are expected to exhibit featureless linear light output curves. However, such thresholdless behavior hinders identification of the laser transition, triggering a long-lasting argument on how to identify the lasing. Here, we demonstrate thresholdless lasing in a semiconductor quantum dot nanolaser with a photonic crystal nanocavity. We employ cavity resonant excitation for enabling the thresholdless operation via focused carrier injection into high cavity field regions...
August 21, 2017: Optics Express
Songkun Ji, Yanhua Hong, Paul S Spencer, Johannes Benedikt, Iwan Davies
Photonic microwave generation based on period-one dynamics of an optically injected VCSEL has been study experimentally. The results have shown that the frequency of the generated microwave signal can be broadly tunable through the adjustment of the injection power and the frequency detuning. Strong optical injection power and higher frequency detuning are favorable for obtaining a high frequency microwave signal. These results are similar to those found in systems based on distributed feedback lasers and quantum dot lasers...
August 21, 2017: Optics Express
Xiongjian Huang, Zaijin Fang, Zixing Peng, Zhijun Ma, Haitao Guo, Jianrong Qiu, Guoping Dong
All solid-state PbS quantum dot (QD)-doped glass precursor fibers avoiding crystallization during fiber-drawing process are successfully fabricated by melt-in-tube technique. By subsequent heat treatment schedule, controllable crystallization of PbS QDs can be obtained in the glass precursor fibers, contributing to broad near-infrared emissions from PbS QD-doped glass fibers. Nevertheless, we find that element-migration and volatilization of sulfur simultaneously happen during the whole fiber-drawing process, because of the huge difference between the melting temperature of core glass and the fiber-drawing temperature...
August 21, 2017: Optics Express
Xue She, Jie Li, Jie-Yun Yan
We investigate the Berry phase in the nanocrystal complex made of a metal nanoparticle and a slowly rotating semiconductor quantum dot under the radiation of a circularly polarized light. The Berry phase in the dynamic system is found to be more effective to manifest the interaction between the plasmon in the metal nanoparticle and the exciton in the quantum dot. The dependences of the Berry phase on the interparticle distance and the relative position are studied in the weak field condition. The methods to observe the Berry phase are also given...
September 18, 2017: Optics Express
Feng Li, Lai You, Chao Nie, Qin Zhang, Xiao Jin, Haiyang Li, Xiaobing Gu, Yan Huang, Qinghua Li
Alloy core/shell CdxZn1-xS/ZnS quantum dots (QDs) are emerging as robust candidates for light-emitting diodes (LEDs), however the emission range of the current CdxZn1-xS/ZnS is quite limited, ranging from 390 to 470 nm. It still remains a challenging task to construct white LEDs based on current CdxZn1-xS/ZnS system. Here, a versatile ZnSe with a moderate band gap is introduced onto the Cd0.1Zn0.9S core. The ZnSe shell, on one hand, can passivate the core surface which leads to bright emissions. On the other hand, it is essential in extending the emission to red region so that the emission wavelengths of Cd0...
September 4, 2017: Optics Express
Luke P Nuttall, Frederic S F Brossard, Stephen A Lennon, Benjamin P L Reid, Jiang Wu, Jonathan Griffiths, Robert A Taylor
In order to demonstrate cavity quantum electrodynamics using photonic crystal (PhC) cavities fabricated around self-assembled quantum dots (QDs), reliable spectral and spatial overlap between the cavity mode and the quantum dot is required. We present a method for using photoresist to optically fabricate heterostructure cavities in a PhC waveguide with a combined photolithography and micro-photoluminescence spectroscopy system. The system can identify single QDs with a spatial precision of ±25 nm, and we confirm the creation of high quality factor cavity modes deterministically placed with the same spatial precision...
October 2, 2017: Optics Express
Paolo Bardella, Lorenzo Luigi Columbo, Mariangela Gioannini
Optical Frequency Comb (OFC) generated by semiconductor lasers are currently widely used in the extremely timely field of high capacity optical interconnects and high precision spectroscopy. In the last decade, several experimental evidences of spontaneous OFC generation have been reported in single section Quantum Dot (QD) lasers. Here we provide a physical understanding of these self-organization phenomena by simulating the multi-mode dynamics of a single section Fabry-Perot (FP) QD laser using a Time-Domain Traveling-Wave (TDTW) model that properly accounts for coherent radiation-matter interaction in the semiconductor active medium and includes the carrier grating generated by the optical standing wave pattern in the laser cavity...
October 16, 2017: Optics Express
Gloria G See, Anming Gao, Lu Xu, Ralph Nuzzo, Songbin Gong, Brian T Cunningham
Quantum dots (QDs) integration into photonic devices requires varied approaches to control and modulate their emission. We demonstrate voltage-tunable PC structures with integrated QDs over suspended piezoelectric aluminum nitride thin film resonators that modulate PC enhancement at MHz frequencies. When the piezoelectric device is actuated at its resonant mechanical frequency, the extracted QD emission direction is likewise modulated via the optical resonant frequency of the PC. Modulation uses nanometer-scale mechanical displacements, offering the potential for greater switching speed and improved mechanical robustness that is not subject to the effects of stiction with a scalable fabrication approach...
October 16, 2017: Optics Express
Jian-Bo Li, Si Xiao, Shan Liang, Meng-Dong He, Jian-Hua Luo, Nam-Chol Kim, Li-Qun Chen
We perform a theoretical study of the bistable four-wave mixing (FWM) response in a coupled system comprised of a semiconductor quantum dot (SQD) and a photonic crystal (PC) nanocavity in which the SQD is embedded. It is shown that the shape of the FWM spectrum can switch among single-peaked, double-peaked, triple-peaked, and four-peaked arising from the vacuum Rabi splitting and the exciton-nanocavity coupling. Especially, we map out bistability phase diagrams within a parameter subspace of the system, and find that it is easy to turn on or off the bistable FWM response by only adjusting the excitation frequency or the pumping intensity...
October 16, 2017: Optics Express
A I Yakimov, V V Kirienko, A A Bloshkin, V A Armbrister, A V Dvurechenskii, J-M Hartmann
We report the fabrication and characterization of a multilayer Ge quantum dot detector grown on Si1-xGex virtual substrate (x = 0.18) for photovoltaic mid-wave infrared photodetection. Detector displays an over 100% photovoltaic response enhancement as compared to a conventional Ge/Si device due to smaller hole effective mass in the SiGe barriers. A further enhancement in sensitivity is achieved by excitation of surface plasmon polariton waves in a Ge/SiGe photodetector coupled with a two-dimensional plasmonic structure...
October 16, 2017: Optics Express
Bin Xie, Yanhua Cheng, Kai Wang, Xiaobing Luo
A recent publication by Shin et al. [Opt. Express25, A113 (2017)] contains an optical simulation model for the quantum dots (QDs) nanophosphor based on the mean free path concept. We show that their measured scattering pattern of QDs is misleading, which would result in a fatal deviation between simulated and actual values.
October 16, 2017: Optics Express
Kaihua Wei, Shanhui Fan, Qingguang Chen, Xiaomin Lai
A passively mode-locked Yb fiber laser using PbSe colloidal quantum dots (CQDs) as saturable absorber (SA) is experimentally demonstrated. An all-fiber experimental scheme was designed to understand the SA property of PbSe CQDs. The non-saturable loss, modulation depth, and saturable intensity of SA measured were 23%, 7%, and 12 MW/cm(2), respectively. The PbSe CQDs were sandwiched in a fiber connector, which was further inserted into the Yb fiber laser for mode-locking. As the pump power up to 110 mW, the self-starting mode-locking pulses were observed...
October 16, 2017: Optics Express
K Rae, C Foucher, B Guilhabert, M S Islim, L Yin, D Zhu, R A Oliver, D J Wallis, H Haas, N Laurand, M D Dawson
Red-, orange-, and green-emitting integrated optoelectronic sources are demonstrated by transfer printing blue InGaN µLEDs onto ultra-thin glass platforms functionally enhanced with II-VI colloidal quantum dots (CQDs). The forward optical power conversion efficiency of these heterogeneously integrated devices is, respectively, 9%, 15%, and 14% for a blue light absorption over 95%. The sources are demonstrated in an orthogonal frequency division multiplexed (OFDM) visible light communication link reaching respective data transmission rates of 46 Mbps, 44 Mbps and 61 Mbps...
August 7, 2017: Optics Express
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