Abstract
1. Introduction
Continuously rapid development of single-photon sources (SPSs) has attracted considerable interest for both the fundamental aspects related to single photons, such as light-matter interaction[
SQDs are treated as one type of atomic-like structure[
Figure 1.(Color online) Single photons emitted from quantum 2-level transition and HBT coincidence counting test.
Researchers have been studying QD SPSs since the single photons were observed in InGaAs QDs in 2000[
In farther research of QD SPSs, there are several urgent challenges to be solved: (1) preparation of individual QDs with controllable wavelength, size, morphologic of and optimization of its emitting effect; (2) the preparation of microcavity with high quality-factor (Q), single QD emitting of microcavity enhancement and optimization of the photon extraction; (3) optimization light collection of external light paths. Significant efforts have been invested into these investigations in our team and have been rewarded with various progresses/achievements. The structure of self-assembled strain-coupled bilayer QDs was firstly investigated for broadening the wavelength of GaAs-based individual InAs QDs from the traditional 0.9 to 1.3 μm, and the 1.3 μm SPSs of high counting rate were triumphantly obtained via integrating this structure into DBR[
2. SQD materials and microcavity
2.1. SQD materials
Not a few materials have been taken account into the candidates of SQDs. All of them have advantages and disadvantages in terms of their single-photon properties[
2.2. Microcavity coupling effect
Coupling a SQD to microcavity is very significant work due to various reasons. It consists of high quantum efficiencies, super repetition rates and outstanding single-photon indistinguishability. Typically, an unrestrained QD randomly emits single photons towards everywhere. Incorporating this QD with a microcavity will directly couple this emission into the cavity mode, which can easily achieve the optical fiber coupling or the free-space optics coupling[
where λc is the cavity resonance wavelength, the spontaneous emission of single QD (or atom as photon emitter) strongly changes by controlling the external dielectric environment[
2.3. Coupling QDs to microcavity for enhancing the emitting of SPSs
For single QD systems, there is merely a little of QD emitting light that escapes from sample and can be collected due to the high refractive index of III–V semiconductors. As shown in Fig. 2, contrasting high refractive index materials such as GaAs (n1 = 3.59) with low refractive index materials such as air (n2 = 1), the inward angle of total reflection is less than θc (θc = sin–1(1/3.59) = 17°). Namely, if the incident photons arrive at the surface of semiconductor, there will be nothing detected by probes besides the total reflection occurs in devices. The solid angle of photons far away from sample is
Figure 2.(Color online) Schematic diagram of (a) inward total reflective angle and (b) the interaction between atom and microcavity[
Moreover, the efficiency of the collected photons is
The ηGaAs is only ~2%, before taking into account the following factors, such as surface roughness, θ < θc, absorption of materials and so on. Therefore, it is important to improve the collected efficiency of photons. Generally, an optical microcavity is used in enhancing the collected efficiency of photons in experiment. Optical microcavity is a kind of micro resonant cavity that possesses a matched length comparing with photonic wavelength at one-dimension (1D) orientation at least. There is characteristic of both the pattern of small volume (V) and high Q, simultaneously. The Q/V of optical microcavity is much larger than the ordinary optical resonant cavity, which leads to the variation of photonic density states[
The traditional optical microcavity is divided into four categories that include Fabry-Pérot (F-P) cavity[
3. In(Ga)As single QD single-photon sources and devices
3.1. Emitting-wavelength scalability of In(Ga)As single QDs
InAs single QDs form at near critical point to island formation, when InAs deposition deviate from that point, QDs either form with high-density or not form QDs at all. Although we have controlled over the growth via MBE instruments, the critical point to island formation varies with the temperature drift, the flux instability, the vacuum background float and the thermal conductivity of different molybdenum pallet. Consequently, it is difficult to prepare single QDs according to fixed header parameters. Gradient flux can broaden the parametric tolerance of indium deposition, which ensures the existence of single QD area on a wafer. The method of in situ desorption can exactly monitor the critical indium deposition (θc, the sacrificial QD layer subsequently desorbs by in situ annealing) of the island formation of sacrificed layer each time by reflection high-energy electron diffraction (RHEED), and then ensures the optimal indium deposition of θ to grow the active QD layer. Due to the similar QD growth conditions for both the sacrificial layer and the active layer, the optimal indium deposition of prepared QDs almost keeps conformance, the ratio of θ/θc is usually independence of temperature and fluxes. According to the experimental experiences and statistical analysis, the stable critical parameters of island formation were found, i.e. the single QD regular criterion θc = 1.7–2.31 monolayer (ML) and the steady parameters of θ/θc[
In fiber quantum communication, it is necessary to develop 1.31 and 1.55 μm SPSs, whereas, the emitting wavelength of individual InAs/GaAs SQDs usually locates at ~0.9 μm. We introduced the strain-coupled bilayer InAs QD structure for the first time to ease the strain accumulation and increase the upper size limit of faultless emitting-light QDs. We broadened the emitting wavelength of InAs/GaAs single QDs to 1.3 μm (Fig. 3) and improving the emitting efficiency by optimizing QD density, growth temperature and introducing charge exciton states. The current work indicates high promises for expanding emitting wavelength to 1.55 μm. After introducing the AlGaAs-barrier layer, the emitting wavelength of InAs/GaAs single QDs could bluely shift to 0.84–0.86 μm. The micro-PL spectrum of 1.3 μm single QDs demonstrated the emitting light of single excitons.
Figure 3.(Color online) Strain-coupled InAs/GaAs single QDs emit at 1.3
The wavelength scalability of QDs can be realized by adding hydrostatic pressure on diamond anvil cell (DAC). On the pressure of 6.58 GPa, the emitting wavelength of 1.3 μm QDs bluely shifts to 0.9 μm and g2(0) is less than 0.3, which represents the single-photon properties of QDs[
3.2. High Q DBR microcavity enhancing the emitting of In(Ga)As single QDs
Batches of GaAs/AlGaAs DBR micropillar microcavities can be prepared together by combining optical exposure and ion etching on a single wafer. Several factors should be considered mainly: (1) matching with the emitting wavelength of single QDs (the precise calibration of DBR thickness and cavity mode); (2) the appropriate upper and down number of DBR pairs; (3) the suitable diameter and shape of micropillar; (4) the fine smoothness of side wall after optimizing the etching processes. The Q varies from hundreds to thousands with different parameters of geometrical technologies. There is multiple-step W-G cavity besides the main F-P cavity mode, when the micropillar diameter surpasses 2 μm. The Q of smooth sidewall W-G is as high as 17 000[
Figure 4.(Color online) Forward and reversed tapered micropillars with smooth facet[
The SPSs of high counting rates were obtained via adjusting the resonance between cavity modes and single QDs. In view of 1.3 μm wavelength strain-coupled bilayer InAs single QDs, the saturated counting rates of single photons arrive at 60000 s–1 by connecting avalanched photon detector (APD) with HBT test header, the emitting speed before arriving at the first lens is calculated to be 3.45 MHz, and the g2(0) is as low as 0.14[
Figure 5.(Color online) Test of 1.3
Due to the high refractive index, the total surface reflection of GaAs is high while the efficiency of emitting is low. We found that integrated GaAs/air-gap HCG on DBR microcavity surface structure that could improve the vertical emitting efficiency and realize the polarization of emitting of single photons. Utilizing the ICP etching in grating graphics, the selective etchant flows through the grating gap into AlGaAs buried layer for corrosion, thus the HCG forms. This complex 3D microcavity has large cavity volume, relaxed process tolerance and easily couples with single QDs.
Confocal optical path of spatial resolution is applied in characterizing the QD single photons. The lights of PL excitation and PL emission were both converged by objective lens. The size of light spot dominates the spatial resolution of xy in-plane, and the space filtering of z-axis takes place in the pinhole of back-end. There is a free-space confocal optical path (Fig. 5, the pinhole is replaced by the slit of spectrometer) and an optical fiber confocal optical path (the pinhole is replaced by the optical fiber core). The single photons can be extracted from the spectra of substrate layer, wetting layer and/or QD layer by grating or filter lens, then they enter APD counting through HBT device after the multi-mode fiber coupling. The efficiency of optical path is severely affected by the stability of system and the precision of focusing. The APD collection efficiency of single photons is generally between 1%–3% through the free-space confocal optical path (Fig. 5). The APD collection efficiency of single photons can arrive at about 7% by optimizing fiber confocal optical path with precise focusing and positioning of device[
3.3. QD growth and single-photon emission in NWs
There are many advantages to growing individual QDs on NWs. The NW growth possesses the high tolerance for lattice mismatch; diversified NWs, such as GaAs, InAs, InP, GaN and InSb, can simultaneously grow on a substrate, and the full-wavelength band QDs can be achieved based on NWs. The spatial discreteness of NWs is beneficial to the control of QD density. The light field of NWs has the distribution of broadband mode (axial waveguide mode and sectional W-G waveguide mode), which can strengthen the QD emitting of different wavelength band and make the light to firmly output from the top of the NWs. The no defect QDs of steep-interface heterojunction can be obtained. The gas-liquid-solid growth of NWs requires droplet catalysis, and Ga droplet is suitable as catalyst because of its no-pollution. The density-controllable GaAs/AlGaAs core/shell-structure NWs of uniform length and orientation can grow on Si substrate by changing the epitaxial rate, time, arsenic (As) pressure, deposition temperature and AlGaAs capping thickness as well as the Y-type bifurcated NWs can be prepared via twice Ga-droplet-catalyzed epitaxy. The InAs/GaAs and GaAs/AlGaAs individual QDs can grow on the sidewall of NWs after excessive InAs and GaAs deposition (Fig. 6). The nucleation progresses of QDs are affected by the surface strain. InAs QDs preferentially grow in the bifurcated position of NWs, because the GaAs/AlGaAs interface strain is larger. GaAs QDs are formed on the sidewall of NWs, and these QDs can emit single photons. The spectrum of InAs/GaAs single QDs presents fine and sharp peaks at 4.2 K, the linewidth is only 101 μeV, and g2(0) is as low as 0.031[
Figure 6.(Color online) InAs (a), GaAs (b) QDs on droplet self-catalyzed NWs and their exciton emission[
3.4. Optical fiber coupling output chip of QD single-photon emitting
Directly using the abovementioned microcavity with optical fiber can guarantee the stability of system and make the related characterizations to be simple, which would enable the single photons to go out of the laboratory. Smoothly laminating the end face of fiber with the light-output side of microcavity, the collected efficiency of emission light depends on the numerical aperture (NA) of fiber and alignment accuracy. The fibers of excited light (650 nm) and emitted (980 nm) light connect with one path of fiber probe via the fused fiber wavelength-division multiplexer (WDM), the single QDs on the sample surface are searched by near-field scanning, and the real-time characterization proceeds after the fiber of emitting connected with fluorescence spectrometer. The sample tank is filled with liquid nitrogen to cool luminescent QDs while the test is on line. The coupling adhesion is finished between single QDs and fiber after the volatilization of liquid nitrogen. This method is applied to realize the single-photon fiber output of NWs[
Figure 7.(Color online) Direct fiber extracted AlGaAs/GaAs QD SPSs[
Owing to the small end face of optical fiber, this adhesive method almost inevitably slopes between fiber and QD chip and affects the emitting collection. Thus, the micropillar array and the single-mode fiber array are adhered by the way of blind alignment, because the fiber array offers the flat end face as the matched adhesive facet of chip and the micropillar cycles ensure the existence of micropillar under each fiber. The single-photon fiber output of 920 nm QDs is realized successfully, the single-photon counting rate of output end arrives at the highest frequency of 420 kHz and g2(0) is as well as 0.02, which imply that the maximum estimate of the receiving single-photon counting rate of fiber coupling surface reaches 1.8 MHz[
Figure 8.(Color online) Direct fiber extracted InAs/GaAs QD SPSs[
3.5. Resonance fluorescence of In(Ga)As single QDs
Resonant excitation can improve the coherence of the QD single photons, while the difficulty is keeping the emitting light apart from exciting light completely. Normally, the vertical QD emitting and collection under lateral excitation can be applied to keep their separation. As shown in Fig. 9, we studied QD RF in cooperated with Muller’s group in University of South Florida[
Figure 9.(Color online) QD RF and single-photon quantum memory.
3.6. Entangled photon emission by the spontaneous parametric down-conversion of QD single photons
We explored the achievement scheme of entangled photon pairs derived from the single photons through nonlinear crystal QD under spontaneous parametric down-conversion (SPDC). The emitting wavelength band of NW QDs locates at 650–780 nm. The exciton emitting peak of NW QDs centered at 775 nm was converted into the entangled photon pairs of 1.55 μm by SPDC through the ultraviolet-light (UV-light) pulsed excitation, the collection of confocal light path, the polarization and the crystal waveguide of periodically poled lithium niobate (PPLN). The nonlinear conversion efficiency of PPLN waveguide is very high, the wide band of 770–780 nm and the tunable output wavelength band of 1550–1600 nm can become real by tuning temperature precisely, and the fidelity of the entangled photon pairs arrives at 91.8%[
3.7. QD single-photon solid-state quantum storage and quantum measurement
Entangled distribution is the core technology to construct the quantum network. The directly entangled distribution can only reach hundred kilometers magnitude in channel due to the channel-transmission loss. The long-distance entangled distribution needs the quantum repeater technology based on single-photon quantum storage and two-photon Bell measurement. So far, the program of quantum repeater verified by experiment are all based on the probabilistic quantum light sources (low generated probability of photons and existing multiphoton pulses). The distribution time of long-range entanglement is estimated to be above the minute magnitude. In cooperation with University of Science and Technology of China, we utilized the self-assembled QDs to generate the deterministic 0.87 μm single photons. The single photons passed through fiber into Nd3+-doped YVO4 crystal that located at another optical platform about 5 m away, the highest 100-time models of deterministic single photons and the minimum of 1-time model quantum storage were realized, thus the number of models got to the highest level[
We collaborated with University of Science and Technology of China, the QD single photons were firstly encoded after polarization and then was used to validate the compromise relationship between the quantum-state measurement and the probability of reversible recovery under weak measurement condition[
4. Summary and outlook
Deterministic self-assembled QDs has been the candidate for fabricating high fidelity SPSs and entangled photon sources. Due to their high purity, high counting rate and excellent coherence under resonant excitation, these unique quantum light sources can be extensively applied in quantum computation, quantum cryptography, quantum teleportation, quantum storage and so on. The practical single-photon devices inevitably require establishing in an appropriate deterministic QD system that possess super emitting speed, high emitting efficiency, excellent collecting efficiency and completed indistinguishability of single photons. Therefore, incorporating SQDs into optical microcavities, that have high spontaneous emission rate due to the enhanced Purcell effect, renders them to be a very fascinating system for the practical SPSs. Subsequently, we demonstrated the related mechanism of microcavity coupling QDs for enhancing the single-photon emission and certain optical microcavities, such as micropillar, are emphatically investigated. Furthermore, Purcell enhancement of coupled microcavities can increase the indistinguishability of SPSs as well, which is suitable to match the spontaneous emission rate enhancement to the optimum value for high indistinguishability[
Ultimately, it is important to resolve the following aspects of QD materials and devices for future developments. Firstly, there is need to purify the surrounding environment of single QDs in order to reduce the jitter of QD spectrum and enhancing the high symmetry QDs, which, in turn, can reduce FSS. Secondly, mastering the precise locating technologies will aid realization of the alignment between the micro-cavity and the single QDs besides with the fiber core for enhancing the excited and collected efficiency of single photons. Thirdly, there is a demand to develop the complex structure of active micro-cavities and the passive waveguides that are suitable for the generation and manipulation of on-chip isotropic single photons, which can be used in HBT meet/Hong-Ou-Mandel interference tests. Furthermore, there is still need to research the integrated quantum chips of high-transmittance waveguide splitters and Mach-Zender interferometers. All abovementioned significant researches will afford the developments for improving the single-photon extraction efficiency of micro-cavity, the collection efficiency of light path and the coincident accounting rates.
Acknowledgments
This work was supported by the National Key Technologies R&D Program of China (Grant No. 2018YFA0306101), the Key R&D Program of Guangdong Province (Grant No. 2018B030329001), the Scientific instrument developing project of the Chinese Academy of Science (Grant No. YJKYYQ20170032), and the National Natural Science Foundation of China (Grant No. 61505196). This work was partly supported by Dr. Xiulai Xu from Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences. We also acknowledged Dr. Xiumei Wang from Wuhan Institute of Physics and Mathematics Chinese Academy of Sciences for the help of results analysis.
References
[1] et alAn electrically pumped polariton laser. Nature, 497, 348(2013).
[2] et alEfficient source of single photons: A single quantum dot in a micropost microcavity. Phys Rev Lett, 89, 233602(2002).
[3] et alVacuum Rabi splitting with a single quantum dot in a photonic crystal nanocavity. Nature, 432, 200(2004).
[4] et alExciton-photon strong-coupling regime for a single quantum dot embedded in a microcavity. Phys Rev Lett, 95, 067401(2005).
[5] Ultralow threshold laser using a single quantum dot and a microsphere cavity. Phys Rev A, 59, 2418(1999).
[6] InAs quantum dots: artificial atoms for solid-state cavity-quantum electrodynamics. Physica E, 9, 131(2001).
[7] et alProbing different regimes of strong field light-matter interaction with semiconductor quantum dots and few cavity photons. New J Phys, 18, 123031(2016).
[8] et alSatellite-to-ground quantum key distribution. Nature, 549, 43(2017).
[9] Quantum computational supremacy. Nature, 549, 203(2017).
[10] et alGround-to-satellite quantum teleportation. Nature, 549, 70(2017).
[11] A scheme for efficient quantum computation with linear optics. Nature, 409, 46(2001).
[12] Quantum computation. Science, 270, 255(1995).
[13] Quantum cryptography based on Bell’s theorem. Phys Rev Lett, 67, 661(1991).
[14] et alQuantum cryptography. Rev Mod Phys, 74, 145(2002).
[15] et alQuantum teleportation of multiple degrees of freedom of a single photon. Nature, 518, 516(2015).
[16] Quantum communication. Nat Photonics, 1, 165(2007).
[17] Single-photon sources. Contemp Phys, 46, 173(2005).
[18] et al''Plug and play'' systems for quantum cryptography. Appl Phys Lett, 70, 793(1997).
[19] et alLimitations on practical quantum cryptography. Phys Rev Lett, 85, 1330(2000).
[20] On-chip single photon sources using planar photonic crystals and single quantum dots. Laser Photon Rev, 4, 499(2010).
[21] et alSingle photon sources with single semiconductor quantum dots. Front Phys, 9, 170(2014).
[22] Single photons on demand from a single molecule at room temperature. Nature, 407, 491(2000).
[23] et alContinuous generation of single photons with controlled waveform in an ion-trap cavity system. Nature, 431, 1075(2004).
[24] Deterministic single-photon source for distributed quantum networking. Phys Rev Lett, 89, 4(2002).
[25] et alStable solid-state source of single photons. Phys Rev Lett, 85, 290(2000).
[26] Energy transfer within ultralow density twin InAs quantum dots grown by droplet epitaxy. ACS Nano, 2, 2219(2008).
[27] et alOn-demand semiconductor single-photon source with near-unity indistinguishability. Nat Nanotechnol, 8, 213(2013).
[28] et alDeterministic coupling of single quantum dots to single nanocavity modes. Science, 308, 1158(2005).
[29] Solid-state single-photon emitters. Nat Photonics, 10, 631(2016).
[30] et alWavelength-tunable entangled photons from silicon-integrated III–V quantum dots. Nat Commun, 7, 10387(2016).
[31] et alSingle InAs quantum dot coupled to different " environments” in one wafer for quantum photonics. Appl Phys Lett, 102, 201103(2013).
[32] Correlation between photons in two coherent beams of light. Nature, 177, 27(1956).
[33] et alA quantum dot single-photon turnstile device. Science, 290, 2282(2000).
[34] et alBias-controlled single-electron charging of a self-assembled quantum dot in a two-dimensional-electron-gas-based n-i-Schottky diode. Phys Rev B, 83, 075306(2011).
[35] et alOptical emission from a charge-tunable quantum ring. Nature, 405, 926(2000).
[36] et alRegulated and entangled photons from a single quantum dot. Phys Rev Lett, 84, 2513(2000).
[37] et alFabrication of InGaAs quantum dots on GaAs(001) by droplet epitaxy. J Cryst Growth, 209, 504(2000).
[38] et alOn-demand single photons with high extraction efficiency and near-unity indistinguishability from a resonantly driven quantum dot in a micropillar. Phys Rev Lett, 116, 020401(2016).
[39] et alSelf-assembled quantum dot structures in a hexagonal nanowire for quantum photonics. Adv Mater, 26, 2710(2014).
[40]
[41] et alElectrically driven quantum dot-micropillar single photon source with 34% overall efficiency. Appl Phys Lett, 96, 011107(2010).
[42] et alA pillar-array based two-dimensional photonic crystal microcavity. Appl Phys Lett, 94, 241110(2009).
[43] Optical microcavities. Nature, 424, 839(2003).
[44] et alNumerical modeling of the coupling efficiency of single quantum emitters in photonic-crystal waveguides. J Opt Soc Am B, 35, 514(2018).
[45] et alHigh-responsivity photodetection by a self-catalyzed phase-pure p-GaAs nanowire. Small, 14, 9(2018).
[46] et alElectrically driven telecommunication wavelength single-photon source. Appl Phys Lett, 90, 063512(2007).
[47] et alAn entangled-light-emitting diode. Nature, 465, 594(2010).
[48] et alSingle-photon-emitting diode at liquid nitrogen temperature. Appl Phys Lett, 93, 101107(2008).
[49] et alElectrically driven quantum dot single-photon source at 2 GHz excitation repetition rate with ultra-low emission time jitter. Appl Phys Lett, 102, 011126(2013).
[50] In: Single Quantum Dots: Fundamentals, Applications and New Concepts. Berlin: Springer-Verlag, 90, 269(2003).
[51]
[52] et alOn-demand generation of indistinguishable polarization-entangled photon pairs. Nat Photonics, 8, 224(2014).
[53] et alNear-transform-limited single photons from an efficient solid-state quantum emitter. Phys Rev Lett, 116, 213601(2016).
[54] et alIndistinguishable tunable single photons emitted by spin-flip raman transitions in InGaAs quantum dots. Phys Rev Lett, 111, 237403(2013).
[55] et alElectric-field-induced energy tuning of on-demand entangled-photon emission from self-assembled quantum dots. Nano Lett, 17, 501(2017).
[56] et alBright single-photon source at 1.3
[57] et alSingle photon extraction from self-assembled quantum dots via stable fiber array coupling. Appl Phys Lett, 110, 142104(2017).
[58] et alSelf-assembly of single "square" quantum rings in gold-free GaAs nanowires. Nanoscale, 6, 3190(2014).
[59] et alSingle InAs quantum dot grown at the junction of branched gold-free GaAs nanowire. Nano Lett, 13, 1399(2013).
[60] et alIn situ probing and integration of single self-assembled quantum dots-in-nanowires for quantum photonics. Nanotechnology, 26, 385706(2015).
[61] et alStorage of multiple single-photon pulses emitted from a quantum dot in a solid-state quantum memory. Nat Commun, 6, 8652(2015).
[62] et alField-field and photon-photon correlations of light scattered by two remote two-level InAs quantum dots on the same substrate. Phys Rev Lett, 109, 267402(2012).
[63] et alCoherent versus incoherent light scattering from a quantum dot. Phys Rev B, 85, 235315(2012).
[64] et alBichromatic resonant light scattering from a quantum dot. Phys Rev B, 89, 155305(2014).
[65] et alExperimental test of the state estimation-reversal tradeoff relation in general quantum measurements. Phys Rev X, 4, 021043(2014).
[66] et alExperimental demonstration of a hybrid-quantum-emitter producing individual entangled photon Pairs in the telecom band. Sci Rep, 6, 26680(2016).
[67] Engineered quantum dot single-photon sources. Rep Prog Phys, 75, 126503(2012).
[68] et alQuantum dot nanostructures and molecular beam epitaxy. Prog Cryst Growth Charact Mater, 47, 166(2003).
[69] Spontaneous emission probabilities at radio frequencies. Phys Rev, 69, 681(1946).
[70] Fundamental limitations in spontaneous emission rate of single-photon sources. Optica, 3, 1418(2016).
[71] et alGrowth of aligned ZnO nanowires via modified atmospheric pressure chemical vapor deposition. Phys Lett A, 380, 3993(2016).
[72] et alProper In deposition amount for on-demand epitaxy of InAs/GaAs single quantum dots. Chin Phys B, 25, 107805(2016).
[73] et alSingle-photon property characterization of 1.3
[74] et alLaser emission from quantum dots in microdisk structures. Appl Phys Lett, 77, 184(2000).
[75] Assembly of hybrid photonic architectures from nanophotonic constituents. Nature, 480, 193(2011).
[76] et alTelecommunication wavelength-band single-photon emission from single large InAs quantum dots nucleated on low-density seed quantum dots. Nanoscale Res Lett, 11, 382(2016).
Set citation alerts for the article
Please enter your email address