1-W, high-repetition-rate room temperature operation of mid-infrared optical parametric oscillator based on periodically poled MgO-doped LiNbO

In this paper a high-repetition-rate mid-infrared （mid-IR） optical parametric oscillator based on periodically poled MgO-doped LiNbO3 （PPMgLN） at room temperature was demonstrated. The maximum average mid-IR output power at 3.63μm was 1.02 W with the repetition rate of 60kHz and corresponding efficiency from the pump to the idler was 26.7%. The temperature tuning and the period tuning characteristics were also discussed.     

Morphological study of atherosclerotic plaque and its application in vulnerability evaluation

The relationships between the morphological characteristics and the vulnerability of atherosclerotic plaque were analyzed theoretically and several suggestions were proposed to evaluate the plaque vulnerability. Validated by animal experiments and clinical studies, the theoretical results were confirmed. Supported by the National Natural Science Foundation of China (Grant Nos. 10302016 and 60402023), the National Basic Research Program of China (973 Program)(Grant No. 2006CB503803), and the National Hi-Tech Research and Development Program of China (863 Program) (Grant No. 2007AA02Z448)     

Threshold quantum secret sharing between multi-party and multi-party

A threshold quantum secret sharing (TQSS) scheme between multi-party and multi-party was proposed using a sequence of single photons, which is useful and efficient when the parties of communication are not all present. We described the process of this TQSS scheme and discussed its security. It was shown that entanglement is not necessary for quantum secret sharing. Moreover, the theoretic efficiency was improved to approach 100% as almost all the instances can be used for generating the private key, and each photon can carry one bit of information. This protocol is feasible with the present-day technique. Supported by the National Basic Research Program of China (973 Program)(Grant No. 2007CB311100), the National High-Technology Research and Development Program of China (Grant Nos. 2006AA01Z419 and 2006AA01Z440), the Major Research Plan of the National Natural Science Foundation of China (Grant No. 90604023), the Scientific Research Common Program of Beijing Municipal Commission of Education (Grant No. KM200810005004), the Scientific Research Foundation for the Youth of Beijing University of Technology (Grant No. 97007016200701), the Doctoral Scientific Research Activation Foundation of Beijing University of Technology (Grant No. 52007016200702), the ISN Open Foundation, and the National Laboratory for Modern Communications Science Foundation of China (Grant No. 9140C1101010601)     

Multiparty simultaneous quantum identity authentication with secret sharing

Two multiparty simultaneous quantum identity authentication (MSQIA) protocols based on secret sharing are presented. All the users can be authenticated by a trusted third party (TTP) simultaneously. In the first protocol, the TTP shares a random key K with all the users using quantum secret sharing. The ith share acts as the authentication key of the ith user. When it is necessary to perform MSQIA, the TTP generates a random number R secretly and sends a sequence of single photons encoded with K and R to all the users. According to his share, each user performs the corresponding unitary operations on the single photon sequence sequentially. At last, the TTP can judge whether the impersonator exists. The second protocol is a modified version with a circular structure. The two protocols can be efficiently used for MSQIA in a network. They are feasible with current technology. Supported by the National Basic Research Program of China (973 Program) (Grant No. 2007CB311100), the National High Technology Research and Development Program of China (Grant Nos. 2006AA01Z419 and 20060101Z4015), the Major Research Plan of the National Natural Science Foundation of China (Grant No. 90604023), the Scientific Research Common Program of Beijing Municipal Commission of Education (Grant No. KM200810005004), the Scientific Research Foundation for the Youth of Beijing University of Technology (Grant No. 97007016200701), the National Research Foundation for the Doctoral Program of Higher Education of China (Grant No. 20040013007), the National Laboratory for Modern Communications Science Foundation of China (Grant No. 9140C1101010601), and the Doctor Scientific Research Activation Foundation of Beijing University of Technology (Grant No. 52007016200702)     

Influence of patterned TiO2/SiO2 dielectric multilayers for back and front mirror facetson GaN-based laser diodes

Ridge InGaN multi-quantum-well-structure （MQW） edge-emitting laser diodes （LDs） were grown on （0001） sapphire substrates by low-pressure metal-organic chemical vapour deposition （MOCVD）. The dielectric TiO2/SiO2 front and back facet coatings as cavity mirror facets of the LDs have been deposited with electron-beam evaporation method. The reflectivity of the designed front coating is about 50% and that of the back high reflective coating is as high as 99.9%. Under pulsed current injection at room temperature, the influences of the dielectric facets were discussed. The threshold current of the ridge GaN-based LDs was decreased after the deposition of the back high reflective dielectric mirrors and decreased again after the front facets were deposited. Above the threshold, the slope efficiency of the LDs with both reflective facets was larger than those with only back facets and without any reflective facets. It is important to design the reflectivity of the front facets for improving the performance of GaN-based LDs.     

Threshold proxy quantum signature scheme with threshold shared verification

A threshold proxy quantum signature scheme with threshold shared verification is proposed. An original signer could authorize a group as its proxy signers. Then only t or more of n persons in the proxy group can generate the proxy signature on behalf of the original signer and any t − 1 or fewer ones cannot do that. When the proxy signature needs to be verified, any t or more of n persons belonging to the verification group can verify the message and any t − 1 or fewer ones cannot verify the validity of the proxy signature. Supported by the National Basic Research Program of China (973 Program)(Grant No. 2007CB311100), the National High-Technology Research and Development Program of China (Grant Nos. 2006AA01Z419 and 20060101Z4015), the Major Research Plan of the National Natural Science Foundation of China (Grant No. 90604023), the Scientific Research Common Program of Beijing Municipal Commission of Education (Grant No. KM200810005004), the Scientific Research Foundation for the Youth of Beijing University of Technology (Grant No. 97007016200701), the Doctoral Scientific Research Activation Foundation of Beijing University of Technology (Grant No. 52007016200702), and the National Laboratory for Modern Communications Science Foundation of China (Grant No. 9140C1101010601)     

An efficient quantum secret sharing protocol with orthogonal product states

An efficient quantum secret sharing protocol with orthogonal product states in the 33 Hilbert space is presented. The particles in the orthogonal product states form two particle sequences. One sequence is sent to Bob and the other is sent to Charlie after rearranging the particle orders. With the help of Alice, Bob and Charlie make the corresponding local measurement to obtain the information of the or- thogonal product states prepared. This protocol has many distinct features such as great capacity and high efficiency.     

Approximate homotopy symmetry method: Homotopy series solutions to the sixth-order Boussinesq equation

An approximate homotopy symmetry method for nonlinear problems is proposed and applied to the sixth-order Boussinesq equation,which arises from fluid dynamics.We summarize the general formulas for similarity reduction solutions and similarity reduction equations of different orders,educing the related homotopy series solutions.Zero-order similarity reduction equations are equivalent to the Painlevé IV type equation or Weierstrass elliptic equation.Higher order similarity solutions can be obtained by solving...     

Deceleration of a continuous-wave （CW） molecular beam with a single quasi-CW semi-Gaussian laser beam

We propose a promising scheme to decelerate a CW molecular beam by using a red-detuned quasi-cw semi-Gaussian laser beam （SGB）. We study the dynamical process of the deceleration for a CW deuterated ammonia （ND3） molecular beam by Monte-Carlo simulation method. Our study shows that we can obtain a ND3 molecular beam with a relative average kinetic energy loss of about 10% and a relative output molecular number of more than 90% by using a single quasi-cw SGB with a power of 1.5kW and a maximum optical well depth of 7.33mK.     

Threshold quantum secure direct communication without entanglement

For the first time, a threshold quantum secure direct communication (TQSDC) scheme is presented. Similar to the classical Shamir's secret sharing scheme, the sender makes n shares, S1, …, Sn of secret key K and each receiver keeps a share secretly. If the sender wants to send a secret message M to the receivers, he en-codes the information of K and M on a single photon sequence and sends it to one of the receivers. According to the secret shares, the t receivers sequentially per-form the corresponding unitary operations on the single photon sequence and ob-tain the secret message M. The shared shares may be reusable if it can be judged that there is no eavesdropper in line. We discuss that our protocol is feasible with current technology.     

Quantum threshold group signature

In most situations, the signer is generally a single person. However, when the message is written on behalf of an organization, a valid message may require the approval or consent of several persons. Threshold signature is a solution to this problem. Generally speaking, as an authority which can be trusted by all members does not exist, a threshold signature scheme without a trusted party appears more attractive. Following some ideas of the classical Shamir’s threshold signature scheme, a quantum threshold group signature one is proposed. In the proposed scheme, only t or more of n persons in the group can generate the group signature and any t − 1 or fewer ones cannot do that. In the verification phase, any t or more of n signature receivers can verify the message and any t − 1 or fewer receivers cannot verify the validity of the signature. Supported by the National Basic Research Program of China (973 Program)(Grant No. 2007CB311100), the National High-Technology Research and Development Program of China (Grant Nos. 2006AA01Z419 and 2006AA01Z440), the Major Research Plan of the National Natural Science Foundation of China (Grant No. 90604023), the Scientific Research Common Program of Beijing Municipal Commission of Education (Grant No. KM200810005004), the Scientific Research Foundation for the Youth of Beijing University of Technology (Grant No. 97007016200701), the Doctoral Scientific Research Activation Foundation of Beijing University of Technology (Grant No. 52007016200702), the ISN Open Foundation, and the National Laboratory for Modern Communications Science Foundation of China (Grant No. 9140C1101010601)     

Revisiting the security of quantum dialogue and bidirectional quantum secure direct communication

From the perspective of information theory and cryptography, the security of two quantum dialogue protocols and a bidirectional quantum secure direct communication (QSDC) protocol was analyzed, and it was pointed out that the transmitted information would be partly leaked out in them. That is, any eavesdropper can elicit some information about the secrets from the public annunciations of the legal users. This phenomenon should have been strictly forbidden in a quantum secure communication. In fact, this problem exists in quite a few recent proposals and, therefore, it deserves more research attention in the following related study. Supported by the National High Technology Research and Development Program of China (Grant No. 2006AA01Z419), the National Natural Science Foundation of China (Grant Nos. 90604023 and 60373059), the National Research Foundation for the Doctoral Program of Higher Education of China (Grant No. 20040013007), the National Laboratory for Modern Communications Science Foundation of China (Grant No. 9140C1101010601), the Natural Science Foundation of Beijing (Grant No. 4072020) and the ISN Open Foundation     

Recursive formulations for the method of reverberation-ray matrix and the application

A recursive formulation is proposed for the method of reverberation-ray matrix (MRRM) to exactly analyze the free vibration of a multi-span continuous rectangular Kirchhoff plate, which has two opposite simply-supported edges. In contrast to the traditional MRRM, numerical stability is achieved by using the present new formulation for high-order frequencies or/and for plates with large span-to-width ratios. The heavy computational cost of storage and memory are also cut down. An improved recursive formulation is further proposed by modifying the iterative formula to reduce the matrix inversion operations. Numerical examples are finally given to demonstrate the effectiveness and efficiency of the proposed recursive formulae. Supported by the National Natural Science Foundation of China (Grant Nos. 10725210, 10832009, and 10432030), the National Basic Research Program of China (Grant No. 2009CB623204), the Specialized Research Fund for the Doctoral Program of Higher Education (Grant No. 20060335107), and the Program for New Century Excellent Talents in University (Grant No. NCET-05-0510)     

Optical bistability and multistability via atomic coherence in the quasi-Λ-type atomic system

The steady-state optical bistability (OB) and optical multistability (OM) behavior in the quasi-Λ-type atomic system driven by a probe field and a coherent coupling field inside a unidirectional ring cavity are shown, and the effects of coupling-field detuning and coupling-field intensity on the OB and OM behavior are investigated. The transition from OB to OM or vice versa is found by varying the detuning of the coherent coupling field or by adjusting the intensity of the coupling field. The influence of the atomic cooperation parameter on the OM behavior is also discussed. Supported by the Natural Science Foundation of Jiangxi of China (Grant No. 2007GZW0819), the National Basic Research Program of China (Grant No. 2005CB724508), and the Foundation of Talent of Jinggang of Jiangxi Province (Grant No. 2008DQ00400)     

Multiferroic behaviour of epitaxial NiFe2O4--BaTiO3 heterostructures

Multiferroic NiFe2O4 （NFO）-BaTiO3 （BTO） bilayered thin films are epitaxially grown on （001） Nb-doped SrTiO3 （STO） substrates by pulsed-laser deposition （PLD）. Different growth sequences of NFO and BTO on the substrate yield two kinds of epitaxial heterostructures with （001）-orientation, i.e. （001）-NFO/（001）-BTO/substrate and （001）- BTO/（001）-NFO/substrate. Microstructure studies from x-ray diffraction （XRD） and electron microscopies show differences between these two heterostructures, which result in different multiferroic behaviours. The heterostructured composite films exhibit good coexistence of both ferroelectric and ferromagnetic properties, in particular, obvious magnetoelectric （ME） effect on coupling response.     

Coupling-induced excitation of a forbidden surface plasmon mode of a gold nanorod

Using the finite-difference time-domain (FDTD) method, we simulate the coupling between a gold nanorod and gold nanoparticles with different plasmonic resonant frequencies/volumes as well as that between the nanorod and a dielectric nanosphere. The influences of coupling with different nanoparticles on the excitation of a forbidden longitudinal surface plasmon mode of the nanorod under normal incidence are investigated. It is found that the cause of this excitation is the broken symmetry of the local electric field experienced by the nanorod resulting from the charge pileup on the other nanoparticle. This result is valuable for understanding the near-field optical characterization of plasmonic metal nanoparticles. Supported by the National Natural Science Foundation of China (Grant Nos. 10821062 and 10804004), the National Basic Research Program of China (Grant No. 2007CB307001), and the Specialized Research Fund for the Doctoral Program of Higher Education (Grant No. 200800011023) Contributed by GONG QiHuang     

Bleustein-Gulyaev waves in a functionally graded piezoelectric material layered structure

This work presents a theoretical study of the propagation behavior of Bleustein-Gulyaev waves in a layered structure consisting of a functionally graded piezoelectric material (FGPM) layer and a transversely isotropic piezoelectric substrate. The influence of the graded variation of FGPM coefficients on the dispersion relations of Bleustein-Gulyaev waves in the layered structure is investigated. It is demonstrated that, for a certain frequency range of Bleustein-Gulyaev waves, the mechanical perturbations of the particles are restricted in the FPGM layer and the phase velocity is independent of the electrical boundary conditions at the free surface. Results presented in this study can not only provide further insight on the electromechanical coupling behavior of surface waves in FGPM layered structures, but also lend a theoretical basis for the design of high-performance surface acoustic wave (SAW) devices. Supported by the National Natural Science Foundation of China (Grant No. 10632060), the National Basic Research Program of China (Grant No. 2006CB601202), the National 111 Project of China (Grant No. B06024), and the Specialized Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20070698064)     

Ambient noise near the sea-route

Ambient noise data measured in an experiment conducted in shallow water near a sea-route were analyzed. It was observed that, at low frequency, the horizontal correlation has an obvious difference from that predicted by the classical ambient noise model. The theoretical analyses show that this phenomenon is caused by wind noise together with the discrete shipping noise nearby. An ambient noise model was proposed to include the effects caused by both the noise sources. Data measured at different times verify that the proposed model can be used to forecast the ambient noise field in shallow water near the sea-route. Supported by the National Natural Science Foundation of China (Grant No. 10734100), the Knowledge Innovation Program of the Chinese Academy of Sciences (Grant No. KZCX1-YW-12-2), the National Basic Research Program of China (Grant No. 2007CB209603), and the Open Foundation of China National Petroleum Corporation Key Laboratory (Grant No. GPKL0804)     

Study of valence intersubband absorption in tensile strained Si/SiGe quantum wells

The hole subband structures and effective masses of tensile strained Si/Sil-yGey quantum wells are calculated by using the 6 × 6 k·p method. The results show that when the tensile strain is induced in the quantum well, the light-hole state becomes the ground state, and the light hole effective masses in the growth direction are strongly reduced while the in-plane effective masses are considerable. Quantitative calculation of the valence intersubband transition between two light hole states in a 7nm tensile strained Si/Si0.55Ge0.45 quantum well grown on a relaxed Si0.5Ge0.5 （100） substrates shows a large absorption coefficient of 8400 cm^-1.     

Comparison between the 3D numerical simulation and experiment of the bubble near different boundaries

Based on the potential flow theory, the vortex ring is introduced to simulate the toroidal bubble, and the boundary element method is applied to simulate the evolution of the bubble. Elastic-plasticity of structure being taken into account, the interaction between the bubble and the elastic-plastic structure is computed by combining the boundary element method (BEM) and the finite element method (FEM), and a corresponding 3D computing program is developed. This program is used to simulate the three-dimensional bubble dynamics in free field, near wall and near the elastic-plastic structure, and the numerical results are compared with the existing experimental results. The error is within 10%. The effects of different boundaries upon the bubble dynamics are presented by studying the bubble dynamics near different boundaries. Supported by the National Natural Science Foundation of China (Grant No. 50779007), the National Science Foundation for Young Scientists of China (Grant No. 50809018), the Specialized Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20070217074), the Defense Advanced Research Program of Science and Technology of Ship Industry (Grant No. 07J1.1.6), and Harbin Engineering University Foundation (Grant No. HEUFT07069)