Quantum field entropy of the system with interaction between moving Bell-state atoms and coherent light field

The field entropy of the system with two moving atoms interacting with the coherent state is investigated by means of the full quantum theory. Under the different initial states with two atoms, the influences of the light field intensity and the atomic motion on the field entropy are discussed. The results indicate that the motion of the atoms leads to strict periodicity in the field entropy evolution. When the two atoms are in the bell state initially, the system is in a completely disentangled state. For the atoms initially at other bell states, the field periodically entangles with the atoms.     

方形半导体量子线中光吸收的横向斯塔克效应

The ground and few excited states of the electrons confined in a square GaAs quantum wire(QW) subjected to an external transverse electric field are investigated using the finite difference method within the effective-mass approximation. When the transverse electric field is applied along a side of the square quantum wire, the calculation of the eigenstates of the quantum wire has an exactly solvable problem whose solutions involve the linear combinations of two independent Airy functions. Compared with the exact analytical results using Airy functions, the results obtained by the use of the finite difference method in terms of the eigenstates of the particle in the QW are in excellent agreement. Subsequently, it is considered that the eigenstates of the particle depend on the orientations of the electric field with respect to the center axis of the QW. It is interesting that the peak value of the energy is found for the field directed along the diagonal in the QW, which can lead to a large energy shift. Meanwhile, dependence of the optical absorption phenomenon in the square QW on the optical field and applied electric field is investigated. It is shown that the optical absorption spectrum depends highly upon the polarization of the optical field and the applied electric field intensities and orientations.     

Magneto-polaron induced intersubband optical transition in a wide band gap Ⅱ–Ⅵ semiconductor quantum dot

Effects of LO-phonon contribution on the electronic and the optical properties are investigated in a Cd0:8Zn0:2Se/ZnSe quantum dot in the presence of magnetic field strength. The magneto-polaron induced hydrogenic binding energy as a function of dot radius in the wide band gap quantum dot is calculated. The oscillator strength and the spontaneous lifetime are studied taking into account the spatial confinement, magnetic field strength and the phonon contribution. Numerical calculations are carried out using variational formulism within the single band effective mass approximation. The optical properties are computed with the compact density matrix method. The magneto-polaron induced optical gain as a function of photon energy is observed. The results show that the optical telecommunication wavelength in the fiber optic communications can be achieved using CdSe/ZnSe semiconductors and it can be tuned with the proper applications of external perturbations.     

Time distribution characteristics of cat-eye reflected light from moving optical target

By using the Collins diffraction formula and expanding the aperture function into a finite sum of complex Gaussian functions, an analytical formula of the time light intensity distribution for oblique Gaussian beams passing through a moving cat-eye optical lens and going back along the entrance way is deduced.By numerical computation,the variation laws of the time intensity distributions of the cat-eye reflected light with the viewing angle,imaging distance,aperture and instantaneous field of view are given.The results show that the relationship between the light intensity at the return place and the detection time is linear,and it is of inverse proportion only when the viewing angle is very large.For the staring imaging optical lens, the nonlinear extent of the time distribution curve becomes larger with the decrease of the viewing angle.For the instanta- neous imaging optical lens,there is still some cat-eye reflected light when the detection system is out of the viewing field of the target lens.     

Theoretical Study on Field Emission Patterns of the Nanotube

The distributions of the electrical potential and field have been given from Maxwell‘s field equations. The results show that there exists very strong electric field intensity on the tip of the nanotube,and the intensity decays rapidly as the distance increases away from the tip. The strong electric field intensity on the tip is consistent with the low threshold voltage under the electric field emission from a nanotube. The calculation also revealed that the higher the aspect ratio is, the stronger the electric field intensity on the tip of the nanotube will be,if the distance and voltage between the cathode and the anode do not change, which predicts the lower threshold voltage under the field emission.     

Linear and Nonlinear Optical Absorptions in Semiparabolic Quantum Wells

By using the compact density matrix approach and iterative procedure, a detailed procedure for the calculation of the linear and nonlinear optical absorption coefficients was given in the electric-field-biased semi parabolic quantum wells(QWs). The simple analytical formulas for the linear and nonlinear optical absorption coefficients in the systems are also deduced. Numerical result on typical GaAs materials shows that,the linear and nonlinear optical absorption coefficients sensitively depend on the applied electric field and the confined potential frequency of the semiparabolic QWs systems as well as the incident optics beam intensity.     

Statics characteristics of two Bose-Einstein condensate dark solitons trapped in an optical lattice

The statics characteristics of two coupled Bose-Einstein condensate （BEC） dark solitons trapped in an optical lattice are investigated with the variational approach. It is found that the interaction between a ‘kink＇ and an ‘anti-kink＇ with opposite phase gradients is effectively repulsive, and the optical lattice can be controllably used to produce a pair of static BEC dark solitons. Its effect depends on the initial location of the BEC dark solitons, the lattice amplitude and wave number.     

Efficient generation of Bell-cat states in remote cavities

In the context of cavity quantum electrodynamics （QED）, a potential scheme is proposed to generate entangled coherent states. The scheme includes twice interactions of two-level atoms with cavities. In the first interaction, two atoms are sent into a microwave cavity with the large detuning respectively. And then the second interaction is that the two atoms enter another microwave cavity and are driven by a resonant classical field meantime. When we choose the proper interaction time and make measurement on the two atoms, the two microwave cavity mode fields are determinatively entangled. In addition, it is easy to generalize the scheme to multi-cavity and multi-atom.     

Efficient generation of Bell-cat states in remote cavities

In the context of cavity quantum electrodynamics (QED),a potential scheme is proposed to generate entangled coherent states. The scheme includes twice interactions of two-level atoms with cavities. In the first interaction,two atoms are sent into a microwave cavity with the large detuning respectively. And then the second interaction is that the two atoms enter another microwave cavity and are driven by a resonant classical field meantime. When we choose the proper interaction time and make measurement on the two atoms,the two microwave cavity mode fields are determinatively entangled. In addition,it is easy to generalize the scheme to multi-cavity and multi-atom.     

Optical fiber magnetic field sensors with peanut-shape structure cascaded with LPFG

An optical fiber magnetic field sensor for the dual-parameter simultaneous measurement is proposed and demonstrated. The sensor head is constructed by a peanut-shape structure and long period fiber grating (LPFG) coated by magnetic fluid (MF). The external magnetic field intensity can be measured by the variation of characteristic wavelength (Dip1 and Dip2) in interference spectrum since the effective refractive index of MF changes with external magnetic field intensity. When the external magnetic field intensity changes from 0 mT to 20 mT, the magnetic field sensitivities of Dip1 and Dip2 are ?0.064 nm/mT and ?0.041 nm/mT, respectively. Experimental results show that the temperature sensitivities of the Dip1 and Dip2 are 0.233 nm/°C and 0.186 nm/°C, respectively. Therefore, the simultaneous measurement of the magnetic field intensity and temperature is demonstrated based on the sensitive matrix. It has some potential applications in aerospace, environmental monitoring and medical sensing fields.     

Optical Gain of V-groove Zn1-xCdxSe/ZnSe Quantum Wires

The subband structures, distributions of electron and hole wave functions, state density, optical gain spectra, and transparency carrier density of the V-groove Zn1-xCdxSe/ZnSe quantum wires are investigated theoretically using four band effective-mass Hamiltonian, which takes into account the effects of the valence band anisotropy and the band mixing. The biaxial strain effect for quantum wires is included in the calculation. The compressive strain in the Zn1-xCdxSe wire region increases the energy separation between the uppermost subbands. The optical gain with xy-polarized light is enhanced, while optical gain with z-polarized light is strongly decreased. The xy-polarized optical gain spectrum has a peak at around 2.541 Ev, with the transparency carrier density of 0.75×1018　cm-3. The calculated results also show that the strain tends to increase the quantum confinement and enhance the anisotropy of the optical transitions.     

Teleportation of an unknown two-particle entangled state via an asymmetric three-particle entanglement state

In this article, a protocol for the teleportation of an unknown two-panicle entanglement is proposed. The feature of the present protocol is that we utilize an asymmetric threeparticle entangled state as the quantum channel. The optimal discrimination between two nonorthogonal quantum states is adopted. It is shown that an unknown two-particle entangled state can be probabilistically teleported from the sender to the remote receiver on condition that the co-sender successfully collaborates. The fidelity in this protocol is one. In addition, the probability of the successful teleportation is calculated and all kinds of transformations performed by the sender and the receiver are provided in detail.     

Enhancement of Crystalline Quality of Strained Straind InAs／InP Quantum Well Structures by Rapid Thermal Annealing

The effect of rapid thermal annealing of the optical properties of a strained InAs/InP single quantum well structrure has investigated in this paper.The luminescence intensity of the quantum well at 8K was increased by a factor of 4 and 1.55meV blue shoft of the quantum well photoluminescence peak was observed af-ter annealing at the optimal condition of 700℃ for 5s.Furthermoer,we found that the luminescence efficiency of the deep radiative levels in the samples was also affected by rapid thermal annealing.Our experimental results have demonstrated that Rapid thermal annealing significantly improves the erystalline quality of strained quantum well struc-tures after growth and is an important way for enhancement of the performance of the laser device.     

应变纤锌矿ZnO/MgxZn1-xO量子点中离子施主束缚激子的光学性质

Within the framework of the effective-mass approximation and the dipole approximation, considering the three-dimensional confinement of the electron and hole and the strong built-in electric field(BEF) in strained wurtzite Zn O/Mg0:25Zn0:75O quantum dots(QDs), the optical properties of ionized donor-bound excitons(D+, X)are investigated theoretically using a variational method. The computations are performed in the case of finite band offset. Numerical results indicate that the optical properties of(D+, X) complexes sensitively depend on the donor position, the QD size and the BEF. The binding energy of(D+, X) complexes is larger when the donor is located in the vicinity of the left interface of the QDs, and it decreases with increasing QD size. The oscillator strength reduces with an increase in the dot height and increases with an increase in the dot radius. Furthermore, when the QD size decreases, the absorption peak intensity shows a marked increment, and the absorption coefficient peak has a blueshift. The strong BEF causes a redshift of the absorption coefficient peak and causes the absorption peak intensity to decrease remarkably. The physical reasons for these relationships have been analyzed in depth.     

Nonlinear Optical Response of Conjugated Polymer to Electric Field

The organic π-conjugated polymers are of major interest materials for the use in electro-optical and nonlinear optical devices. In this work, for a selected polyacetylene chain, the optical absorption spectra in UV/Vis regime as well as the linear polarizabilitiy and nonlinear hyperpolarizability are calculated by using quantum chemical ab initio and semiempirical methods. The relationship of its optical property to electric field is obtained. Some physical mechanism of electric field effect on molecular optical property is discussed by means of electron distribution and intramolecular charge transfer.     

Influence of Disassociation Probability on External Quantum Efficiency in Organic Electrophosphorescent Devices

An analytical model is presented to calculate the disassociation probability and the external quantum efficiency at high field in doped organic electrophosphorescence（EPH） devices. The charge recombination process and the triplet（T）-triplet（T） annihilation processes are taken into account in this model. The influences of applied voltage and the thickness of the device on the disassociation probability, and of current density and the thickness of the device on the external quantum efficiency are studied thoroughly by including and ignoring the disassociation of excitons. It is found that the dissociation probability of excitons will come close to 1 at high electric field, and the external EPH quantum efficiency is almost the same at low electric field. There is a large discrepancy of the external EPH quantum efficiency at high electric field for including or ignoring the disassociation of excitons.     

Single photon-chiral phonon entanglement in monolayer WSe2

Entanglement is a defining feature of quantum physics with no classical analog. On the one hand, it is a powerful concept used in the fundamental study of quantum systems, many-body physics and even black hole physics. On the other hand, it is a key resource in quantum communication and information processing. Entanglement has been realized between photons[1], ions[2], spins[3], quantum dots[4] and even larger objects such as macroscopic diamonds[5]. Entanglement involving macroscopic objects is particularly intriguing and holds promise for novel quantum technologies. In a recent paper[6] published in Nature Physics, Srivastava and coworkers have unveiled an intriguing entanglement between collective and macroscopic vibration involving billions of atoms of the crystal (phonon) and a single optical excitation of a quantum dot (QD) in monolayer WSe2 (Fig. 1(a)). This is the first report on single photon entangled with phonon.     

Vacuum Sensitivity of Photovoltage of AlGaAs／GaAs Multiple Quantum Wells^①②

The photovoltage spectra of AlGaAs/GaAs multiple quantum wells at different vacuum have been measured and the vacuum sensitivity of photovoltage in reported.The experimental results show that the photovoltage decreases in a step-like manner at 10^5 Pa and increases in a sept-like manner at 0.1Pa.It is believed that the variation of photovoltage with vacuum is due to the action of oxygen atoms adsorbing at the surface of AlGaAs/GaAs multiple quantum wells structure.     

Optical Gain of V—groove Zn1—xCdxSe／ZnSe Quantum Wires

The subband structures, distributions of electron and hole wave functions, state density, optical gain spectra, and transparency carrier density of the V-groove Zn 1-x Cd x Se/ZnSe quantum wires are investigated theoretically using four band effective-mass Hamiltonian, which takes into account the effects of the valence band anisotropy and the band mixing. The biaxial strain effect for quantum wires is included in the calculation. The compressive strain in the Zn 1-x Cd x Se wire region increases the energy separation between the uppermost subbands. The optical gain with xy -polarized light is enhanced, while optical gain with z -polarized light is strongly decreased. The xy -polarized optical gain spectrum has a peak at around 2.541 eV, with the transparency carrier density of 0.75×10 18 cm -3 . The calculated results also show that the strain tends to increase the quantum confinement and enhance the anisotropy of the optical transitions.     

Structure and photoluminescence properties of InN films grown on porous silicon by MOCVD

In this work, indium nitride (InN) films were successfully grown on porous silicon (PS) using metal oxide chemical vapor deposition (MOCVD) method. Room temperature photoluminescence (PL) and field emission scanning electron microscopy (FESEM) analyses are performed to investigate the optical, structural and morphological properties of the InN/PS nanocomposites. FESEM images show that the pore size of InN/PS nanocomposites is usually less than 4 μm in diameter, and the overall thickness is approximately 40 μm. The InN nanoparticles penetrate uniformly into PS layer and adhere to them very well. Nitrogen (N) and indium (In) can be detected by energy dispersive spectrometer (EDS). An important gradual decrease of the PL intensity for PS occurs with the increase of oxidation time, and the PL intensity of PS is quenched after 24 h oxidization. However, there is a strong PL intensity of InN/PS nanocomposites at 430 nm (2.88 eV), which means that PS substrate can influence the structural and optical properties of the InN, and the grown InN on PS substrate has good optical quality.