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Acceleration of ions from ultrathin foils irradiated by intense circularly polarized laser pulses is investigated using a one-dimensional particle-in-cell code. As a circularly polarized laser wave heats the electrons much less efficiently than the wave of linear polarization, the ion can be synchronously accelerated and bunched by the electrostatic field, thus a monoenergetic and high intensity proton beam can be generated.

The interaction of ultrashort intense circularly polarized laser with ultra thin overdense foil is studied by particle-in-cell simulation and analytic model. It is found that with the balance between pondermotive force and electrostatic force, highly quasi-monoenergetic proton beam can be generated by Phase Stable Acceleration (PSA) process. As in conventional accelerators, ion will be accelerated and bunched up in the longitudinal direction at the same time.

A real-time ion spectrometer mainly based on a high-resolution Thomson parabola and a plastic scintillator is designed and developed. The spectrometer is calibrated by protons from an electrostatic accelerator. The feasibility and reliability of the diagnostics are demonstrated in laser-driven ion acceleration experiments performed on the XL-II laser facility. The proton spectrum extrapolated from the scintillator data is in excellent agreement with the CR39 spectrum in terms of beam temperature and the cutoff energy. This real-time spectrometer allows an online measurement of the ion spectra in single shot, which enables efficient and statistical studies and applications in high-repetition-rate laser acceleration experiments.

We present a theoretical and experimental study on the bandwidth of parametric down-converted photons generated from periodically poled lithium niobate (PPLN) crystal pumped by a pulsed laser. By comparison of crystals with different lengths and pump beams of different bandwidths, we demonstrate that the bandwidth of down-converted photons will increase for a broader bandwidth of pump pulse and decrease for a longer crystal, but the influence of crystal length will become weaker along with increase of both crystal length and pump pulse bandwidth. Especially under the conditions of our experiment, the bandwidth almost remains unchanged for longer crystals when pumped by a femtosecond laser. This may be helpful for schemes in which pulsed lasers are used to pump PPLN crystals.

Quantum coherence is the most distinct feature of quantum mechanics. However, inevitable decoherence processes will finally destroy it and make the "Schrodinger's cat" invisible in our classical world. In this "quantum-to-classical transition", the so-called "largeness" plays a critical role. We experimentally study the largeness phenomena in the bipartite entanglement decay process through a depolarizing channel with two-photon entangled states generated from a spontaneous parametric down-conversion source. Our experiment demonstrates how the speed of entanglement decay and the time when "entanglement sudden death" happens depend on the size of the system exposed to the environment noise.

LiNi1-y CoyO2 (0.1 ≤ y ≤ 0.4) positive electrode materials are synthesized by a chemical method with stoichiometric acetates of related cations. Their crystal structure, stoichiometry and electrochemical behaviors versus Co concentration are investigated by x-ray diffraction, synchrotron-based x-ray absorption fine structure and galvanostatic cycling measurements. The results reveal that the non-stoichiometric Ni2+, Li/Ni cation mixing and polarization are reduced as the amount of Co substitution increases, clearly indicating that the Co element is a medium for easily oxidizing Ni2+ to Ni3+ during the synthesis process.

We present a wavelength-tunable narrow-band fiber-coupled source to generate correlated photon pairs at 539nm and 1550nm. Using a 10-mm PPLN crystal, we obtain more than 50mm tunable range near 1550nm. This source, given its spectral property and tunable property, is well suited for tasks in fiber-optic quantum communication and cryptography networks.