The polaron effect in a quantum dot quantum well (QDQW)system is investigated by using the perturbation method. Both the bound electron states outside and inside the shell well are taken into account . Numerical calcu...The polaron effect in a quantum dot quantum well (QDQW)system is investigated by using the perturbation method. Both the bound electron states outside and inside the shell well are taken into account . Numerical calculation on the CdS/HgS QDQW shows that the phonon correction to the electron ground state energy is quite significant and cannot be neglected.展开更多
The problem of bound polarons in quantum dot quantum well (QDQW) structures is studied theoretically. The eigenfrequencies of bulk longitudinal optical (LO) and surface optical (SO) modes are derived in the fram...The problem of bound polarons in quantum dot quantum well (QDQW) structures is studied theoretically. The eigenfrequencies of bulk longitudinal optical (LO) and surface optical (SO) modes are derived in the framework of the dielectric continuum approximation. The electron-phonon interaction Hamiltonian for QDQW structures is obtained and the exchange interaction between impurity and LO-phonons is discussed. The binding energy and the trapping energy of the bound polaron in CdS/HgS QDQW structures are calculated. The numerical results reveal that there exist three branches of eigenfrequencies of surface optical vibration in the CdS/HgS QDQW structure. It is also shown that the binding energy and the trapping energy increase as the inner radius of the QDQW structure decreases, with the outer radius fixed, and the trapping energy takes a major part of the binding energy when the inner radius is very small.展开更多
Electron Raman scattering (ERS) is investigated in a spherical HgS/CdS quantum dot quantum well (QDQW). The differential cross section (DCS) is calculated as a function of the scattering frequency and the sizes ...Electron Raman scattering (ERS) is investigated in a spherical HgS/CdS quantum dot quantum well (QDQW). The differential cross section (DCS) is calculated as a function of the scattering frequency and the sizes of QDQW. Single parabolic conduction and valence bands are assumed. The selection rules for the processes are studied. Singularities in the spectra are found and interpreted. The ERS studied here can be used to provide direct information about the electron band structure of these systems.展开更多
Excited states of lnAs quantum dots (QDs) can be energetically coupled with the confined level of OaAs quantum wells (QWs) in a thin-barrier resonant tunneling diode (RTD). Single charge variation in the coupled...Excited states of lnAs quantum dots (QDs) can be energetically coupled with the confined level of OaAs quantum wells (QWs) in a thin-barrier resonant tunneling diode (RTD). Single charge variation in the coupled QD can effectively switch on/off the resonant tunneling current passing through RTD, not only for emcient single-photon detection but also for photon-number-resolving detection. We present the study of the Q,D-QW coupling effect in the quantum dot coupled resonant tunneling diode (QD-cRTD) and figure out important factors for further improving the detector performance.展开更多
The ZnO quantum dots(QDs) were synthesized with improved chemical solution method.The size of the ZnO QDs is exceedingly uniform with a diameter of approximately 4.8 nm,which are homogeneously dispersed in ethanol.T...The ZnO quantum dots(QDs) were synthesized with improved chemical solution method.The size of the ZnO QDs is exceedingly uniform with a diameter of approximately 4.8 nm,which are homogeneously dispersed in ethanol.The optical absorption edge shifts from 370 nm of bulk material to 359 nm of QD materials due to the quantum size effect,while the photoluminescence peak shifts from 375 nm to 387 nm with the increase of the density of ZnO QDs.The stability of ZnO QDs was studied with different dispersion degrees at 0?C and at room temperature of 25?C.The agglomeration mechanisms and their relationship with the emission spectra were uncovered for the first time.With the ageing of Zn O QDs,the agglomeration is aggravated and the surface defects increase,which leads to the defect emission.展开更多
Nano-sized quantum dots(QDs) exhibit uniquely optical properties that are tunable with different sizes and shapes.QDs can emit narrow symmetric bands under a wide excitation range,possess antiphotobleaching stabilit...Nano-sized quantum dots(QDs) exhibit uniquely optical properties that are tunable with different sizes and shapes.QDs can emit narrow symmetric bands under a wide excitation range,possess antiphotobleaching stability,and be bio-functionalized on the large surface area.Therefore,QDs are attractive vectors for imaging-guided therapy.Small-interfering RNA(siRNAs)-based therapeutics hold great potential to target a large part of the currently undruggable genes,but overcoming the lipid bilayer to deliver siRNA into cells has remained a major challenge to solve for widespread development of siRNA therapeutics.In this mini-review,we focus on theranostic QD/siRNA assembles for enhancing delivery of siRNA and facilitating evaluation of therapeutic efficacy via imaging of QDs,with special attention to carbonaceous QDs for delivery of siRNA.展开更多
We report here a nanostructure that traps single quantum dots for studying strong cavity-emitter coupling. The nanostructure is designed with two elliptical holes in a thin silver patch and a slot that connects the ho...We report here a nanostructure that traps single quantum dots for studying strong cavity-emitter coupling. The nanostructure is designed with two elliptical holes in a thin silver patch and a slot that connects the holes. This structure has two functionalities:(1) tweezers for optical trapping;(2) a plasmonic resonant cavity for quantum electrodynamics. The electromagnetic response of the cavity is calculated by finite-difference time-domain(FDTD) simulations, and the optical force is characterized based on the Maxwell's stress tensor method. To be tweezers, this structure tends to trap quantum dots at the edges of its tips where light is significantly confined. To be a plasmonic cavity, its plasmonic resonant mode interacts strongly with the trapped quantum dots due to the enhanced electric field. Rabi splitting and anti-crossing phenomena are observed in the calculated scattering spectra, demonstrating that a strong-coupling regime has been achieved. The method present here provides a robust way to position a single quantum dot in a nanocavity for investigating cavity quantum electrodynamics.展开更多
We report on a quantum dot quantum cascade detector(QD-QCD), whose structure is derived from a QD cascade laser. In this structure, more ordered In As QD layers formed in the Stranski-Krastanow growth mode on a thin...We report on a quantum dot quantum cascade detector(QD-QCD), whose structure is derived from a QD cascade laser. In this structure, more ordered In As QD layers formed in the Stranski-Krastanow growth mode on a thin Ga As buffer layer are incorporated into the active region. This QD-QCD can operate up to room temperature with a peak detection wavelength of 5.8 μm. A responsivity of 3.1 mA/W at 160 K and a detectivity of 3.6 × 10~8 Jones at 77 K are obtained. The initial performance of the detector is promising, and, by further optimizing the growth of InA s QDs, integrated QD-quantum cascade laser/QCD applications are expected.展开更多
Continuous wave operation of a semiconductor laser diode based on five stacks of InAs quantum dots (QDs) embedded within strained InGaAs quantum wells as an active region is demonstrated. At room temperature, 355-mW...Continuous wave operation of a semiconductor laser diode based on five stacks of InAs quantum dots (QDs) embedded within strained InGaAs quantum wells as an active region is demonstrated. At room temperature, 355-mW output power at ground state of 1.33-1.35 μm for a 20-μm ridge-waveguide laser without facet coating is achieved. By optimizing the molecular beam epitaxy (MBE) growth conditions, the QD density per layer is raised to 4 × 10^10 cm^-2. The laser keeps lasing at ground state until the temperature reaches 65 ℃.展开更多
文摘The polaron effect in a quantum dot quantum well (QDQW)system is investigated by using the perturbation method. Both the bound electron states outside and inside the shell well are taken into account . Numerical calculation on the CdS/HgS QDQW shows that the phonon correction to the electron ground state energy is quite significant and cannot be neglected.
基金supported by Universities Program of Inner Mongol of China(Grant No NJZZ07008)the Natural Science Foundation of Inner Mongol of China(Grant No 200607010105)
文摘The problem of bound polarons in quantum dot quantum well (QDQW) structures is studied theoretically. The eigenfrequencies of bulk longitudinal optical (LO) and surface optical (SO) modes are derived in the framework of the dielectric continuum approximation. The electron-phonon interaction Hamiltonian for QDQW structures is obtained and the exchange interaction between impurity and LO-phonons is discussed. The binding energy and the trapping energy of the bound polaron in CdS/HgS QDQW structures are calculated. The numerical results reveal that there exist three branches of eigenfrequencies of surface optical vibration in the CdS/HgS QDQW structure. It is also shown that the binding energy and the trapping energy increase as the inner radius of the QDQW structure decreases, with the outer radius fixed, and the trapping energy takes a major part of the binding energy when the inner radius is very small.
基金Project supported by the Guangdong Provincial Natural Science Foundation(No.S2012010010976)
文摘Electron Raman scattering (ERS) is investigated in a spherical HgS/CdS quantum dot quantum well (QDQW). The differential cross section (DCS) is calculated as a function of the scattering frequency and the sizes of QDQW. Single parabolic conduction and valence bands are assumed. The selection rules for the processes are studied. Singularities in the spectra are found and interpreted. The ERS studied here can be used to provide direct information about the electron band structure of these systems.
基金Supported by the National Basic Research Program of China under Grant No 2011CB925600the National Natural Science Foundation of China under Grant Nos 11427807,91321311,10990100,11174057 and 61106092the Shanghai Science and Technology Committee under Grant No 14JC1406600
文摘Excited states of lnAs quantum dots (QDs) can be energetically coupled with the confined level of OaAs quantum wells (QWs) in a thin-barrier resonant tunneling diode (RTD). Single charge variation in the coupled QD can effectively switch on/off the resonant tunneling current passing through RTD, not only for emcient single-photon detection but also for photon-number-resolving detection. We present the study of the Q,D-QW coupling effect in the quantum dot coupled resonant tunneling diode (QD-cRTD) and figure out important factors for further improving the detector performance.
基金Project supported by the FRFCU(Grant No.2016JBM066)863 Program(Grant No.2013AA032205)+1 种基金the National Natural Science Foundation of China(Grant Nos.61575019,51272022,and 11474018)RFDP(Grant Nos.20120009130005 and 20130009130001)
文摘The ZnO quantum dots(QDs) were synthesized with improved chemical solution method.The size of the ZnO QDs is exceedingly uniform with a diameter of approximately 4.8 nm,which are homogeneously dispersed in ethanol.The optical absorption edge shifts from 370 nm of bulk material to 359 nm of QD materials due to the quantum size effect,while the photoluminescence peak shifts from 375 nm to 387 nm with the increase of the density of ZnO QDs.The stability of ZnO QDs was studied with different dispersion degrees at 0?C and at room temperature of 25?C.The agglomeration mechanisms and their relationship with the emission spectra were uncovered for the first time.With the ageing of Zn O QDs,the agglomeration is aggravated and the surface defects increase,which leads to the defect emission.
基金supported by the National Natural Science Foundation of China(No.81602699)the National High Technology Research and Development Program of China(No.2015AA020309)the China Postdoctoral Science Foundation funded project(No.2015M570791)
文摘Nano-sized quantum dots(QDs) exhibit uniquely optical properties that are tunable with different sizes and shapes.QDs can emit narrow symmetric bands under a wide excitation range,possess antiphotobleaching stability,and be bio-functionalized on the large surface area.Therefore,QDs are attractive vectors for imaging-guided therapy.Small-interfering RNA(siRNAs)-based therapeutics hold great potential to target a large part of the currently undruggable genes,but overcoming the lipid bilayer to deliver siRNA into cells has remained a major challenge to solve for widespread development of siRNA therapeutics.In this mini-review,we focus on theranostic QD/siRNA assembles for enhancing delivery of siRNA and facilitating evaluation of therapeutic efficacy via imaging of QDs,with special attention to carbonaceous QDs for delivery of siRNA.
基金National Key R&D Program of China(2016YFA0301300)
文摘We report here a nanostructure that traps single quantum dots for studying strong cavity-emitter coupling. The nanostructure is designed with two elliptical holes in a thin silver patch and a slot that connects the holes. This structure has two functionalities:(1) tweezers for optical trapping;(2) a plasmonic resonant cavity for quantum electrodynamics. The electromagnetic response of the cavity is calculated by finite-difference time-domain(FDTD) simulations, and the optical force is characterized based on the Maxwell's stress tensor method. To be tweezers, this structure tends to trap quantum dots at the edges of its tips where light is significantly confined. To be a plasmonic cavity, its plasmonic resonant mode interacts strongly with the trapped quantum dots due to the enhanced electric field. Rabi splitting and anti-crossing phenomena are observed in the calculated scattering spectra, demonstrating that a strong-coupling regime has been achieved. The method present here provides a robust way to position a single quantum dot in a nanocavity for investigating cavity quantum electrodynamics.
基金supported by the National Basic Research Program of China(No.2013CB632804/02)the National Natural Science Foundation of China(Nos.61376501,61404131,and 11274301)
文摘We report on a quantum dot quantum cascade detector(QD-QCD), whose structure is derived from a QD cascade laser. In this structure, more ordered In As QD layers formed in the Stranski-Krastanow growth mode on a thin Ga As buffer layer are incorporated into the active region. This QD-QCD can operate up to room temperature with a peak detection wavelength of 5.8 μm. A responsivity of 3.1 mA/W at 160 K and a detectivity of 3.6 × 10~8 Jones at 77 K are obtained. The initial performance of the detector is promising, and, by further optimizing the growth of InA s QDs, integrated QD-quantum cascade laser/QCD applications are expected.
基金This work was supported by the Major State Key Basic Research Program (No. TG2000036603) the National "863" Program of China (No. 2002AA312080) and the National Natural Science Foundation of China (No. 60137020).
文摘Continuous wave operation of a semiconductor laser diode based on five stacks of InAs quantum dots (QDs) embedded within strained InGaAs quantum wells as an active region is demonstrated. At room temperature, 355-mW output power at ground state of 1.33-1.35 μm for a 20-μm ridge-waveguide laser without facet coating is achieved. By optimizing the molecular beam epitaxy (MBE) growth conditions, the QD density per layer is raised to 4 × 10^10 cm^-2. The laser keeps lasing at ground state until the temperature reaches 65 ℃.