Zhu Shining

Quantum Secure Direct Communication by Using Three-Dimensional Hyperentanglement

We propose two schemes for realizing quantum secure direct communication (QSDC) by using a set of ordered two-photon three-dimensional hyperentangled states entangled in two degrees of freedom (DOFs) as quantum information channels. In the first scheme, the photons from Bob to Alice are transmitted only once. After insuring the security of the quantum channels, Bob encodes the secret message on his photons. Then Alice performs single-photon two-DOF Bell bases measurements on her photons. This scheme has better security than former QSDC protocols. In the second scheme, Bob transmits photons to Alice twice. After insuring the security of the quantum channels, Bob encodes the secret message on his photons. Then Alice performs two-photon Bell bases measurements on each DOF. The scheme has more information capacity than former QSDC protocols.

Linear entropies in the Jaynes–Cummings model with intensity-dependent coupling in a phase-damped cavity

We investigate the evolution of a quantum system described by the Jaynes–Cummings model with an arbitrary form of intensity-dependent coupling by displaying the linear entropies of the atom, field and atom–field system in the large detuning approximation. The cavity field is assumed to be coupled to a reservoir with a phase-damping coupling. The effects of cavity phase damping on the entanglement and coherence loss of such a system are studied.

Pulsed Laser Deposition of Optical Waveguiding LiNbO3 Films on SiO2 Substrate

The optical waveguiding lithium niobate (LiNbO3) films have been prepared on (001)-oriented SiO2 substrates by pulsed laser deposition technique. The x-ray diffraction and scanning electron microscopy were used to characterize the as-grown films, and revealed that highly (012)-textured LiNbO3 films with smooth surface were achieved. The optical waveguiding properties of these films were demonstrated by m-line measurements of transverse-magnetic and transverse-electric multimodes.

Optical Anisotropic Properties of m-Plane GaN Film Grown by Metalorganic Chemical Vapor Deposition

Abstract Spontaneous and piezoelectric polarization could lower the efficiency of GaN-based light-emitting diodes. In order to eliminate or reduce this undesirable effect, m-plane GaN film was prepared by metalorganic chemical vapor deposition (MOCVD) on LiAlO 2 (100) substrate with a GaN buffer layer. Since the c axis of the m-plane GaN lays in the grown plane, the breakage of in-plane symmetry gave rise to an optical anisotropy, which was revealed by a difference in refractive indexes of E-field parallel and perpendicular to the c axis of the m-plane GaN measured by polarized reflection measurement. In addition, in-plane strain anisotropy due to the lattice mismatch between the GaN film and the LiAlO 2 substrate changed the Electronic Band Structure (EBS). The change of EBS also led to an in-plane optical anisotropy. Polarized absorption and Photoluminescence (PL) measurements showed a split in energy of 32 meV for optical absorption edge and 37 meV for PL peak energy respectively.

Generating a 2.4-W cw Green Laser by Intra-Cavity Frequency Doubling of a Diode-Pumped Nd:GdVO4 Laser with a MgO:PPLN Crystal

High-power cw green laser radiation is generated by intra-cavity frequency doubling of a diode-pumped Nd:GdVO4 laser with a MgO-doped periodically-poled LiNbO3 (MgO:PPLN) crystal at room temperature. An average power of 2.4 W at 0.53 μm is obtained under the pump 15 W at 808 nm, corresponding to an overall optical-to-optical conversion efficiency of 16%. The M2 factor of the green beam is 3.90 and 1.34 for the horizontal and vertical direction, respectively. In addition, the power fluctuation is measured to be about ±5%.

Entropy squeezing of the field interacting with a nearly degenerate V-type three-level atom

The position- and momentum-entopic squeezing properties of the optical field in the system of a nearly degenerate three-level atom interacting with a single-mode field are investigated. Calculation results indicate that when the field is initially in the vacuum state, it may lead to squeezing of the position entropy or the momentum entropy of the field if the atom is prepared properly. The effects of initial atomic state and the splitting of the excited levels of the atom on field entropies are discussed in this case. When the initial field is in a coherent state, we find that position-entropy squeezing of the field is present even if the atom is prepared in the ground state. By comparing the variance squeezing and entropy squeezing of the field we confirm that entropy is more sensitive than variance in measuring quantum fluctuations.

Numerical simulations of negative-index refraction in a lamellar composite with alternating single negative layers

Negative-index refraction is demonstrated in a lamellar composite with epsilon-negative (ENG) and mu-negative (MNG) materials stacked alternatively. Based on the effective medium approximation, simultaneously negative effective permittivity and permeability of such a lamellar composite are obtained theoretically and further proven by full-wave simulations. Consequently, the renowned left-handed metamaterial comprising split ring resonators and wires is interpreted as an analogy of such ENG–MNG layers. In addition, beyond the effective medium approximation, the propagating field squeezed near the ENG/MNG interface is demonstrated to be left-handed surface waves with backward phase velocity.Negative-index refraction is achieved in a lamellar composite with epsilon-negative (ENG) and mu-negative (MNG) materials stacked alternatively. Based on the effective medium approximation, simultaneously negative effective permittivity and permeability of such a lamellar composite are obtained theoretically and further proven by full-wave simulations. Consequently, the famous left-handed metamaterial comprising split ring resonators and wires is interpreted as an analogy of such an ENG-MNG lamellar composite. In addition, beyond the effective medium approximation, the propagating field squeezed near the ENG/MNG interface is demonstrated to be left-handed surface waves with backward phase velocity.

Raman scattering in Fibonacci metallic superlattices

Raman scattering experiments from acoustic phonons in Fibonacci metallic Nb-Cu superlattices were performed. The main features of the experimental results show that the Raman spectrum is dominated by triplet peaks which originate from the density of states of longitudinal-acoustic (LA) phonons in the subbands of phonon dispersion. The expected rich structure of gaps in the phonon spectrum has been labeled by strongest diffraction wave vector factor nτp.

Red and Blue Light Generation in an LiTaO3 Crystal with a Double Grating Domain Structure

The Pd39Ni10Cu30P21 bulk metallic glass is isothermally relaxed under various pressures. The degree of the structural relaxation is evaluated in terms of the enthalpy recovery behaviours involved in the irreversible glass transition processes by using a temperature-modulated differential scanning calorimetry technique. A roughly Linear increase of the recovery enthalpy is observed within the experimental pressure range fi-om 2.67 to 4.45 GPa, which reflects the release of the frozen-in enthalpy in the as-quenched glass with increasing relaxation pressure. The pressure dependence of the timescale of the enthalpy recovery processes is also exhibited.

Single Pass Third-Harmonic Generation of 310 mW of 355 nm with an All-Solid-State Laser

A maximum of 310 mW average output power at 355 nm has been obtained by extracavity frequency tripling with a BBO crystal in a Q-switched Nd:YVO4 laser with 11.2 W of laser diode pump power. The single pass frequency conversion efficiency (infrared-to-ultraviolet) is 14.3%. The power stability of the ultraviolet laser is better than 1% in 30 min.