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A low-pump-threshold high-repetition-rate intracavity optical parametric generator (IOPG) by using a periodically poled lithium niobate (PPLN) is reported. The PPLN, which is 18.7 mm long and has a grating period of 28.93 μm at room temperature, is inserted in a diode-end-pumped Nd:YVO4 laser with an acousto-optic Q switch. The parametric generation threshold is 1.3 W (diode laser power) at a Q-switch repetition rate of 19 kHz. At an incident diode pump power of 5 W, an average signal output power of 280 mW has been achieved. The signal pulse duration is approximately 85 ns. By changing the crystal temperature from 120°C to 250°C, the signal wavelength can be tuned from 1.493 μm to 1.538 μm.

A simplified scheme of bend-induced mode distortion is introduced into bent holey fibres, the distorted mode distribution and mode effective area reduction are investigated using the finite difference method. Numerical results show that the modes of bent holey fibres with small bend radius shift away from the core and are deformed greatly, and the mode areas drop significantly as the bend radius decreases, which severely affects the fibre laser performance. The propagation characteristics of bent holey fibres at given wavelength are determined by fill factor and normalized bend radius. Finally, the transition normalized bend radius that represents the location of the mode area beginning to fall off is obtained.

We report an efficient nanosecond optical parametric generator (OPG) with a periodically-phase-reversed periodically poled MgO:LiNbO3(ppr-PPMgLN), which produces two pairs of signal and idler waves. The OPG is pumped by a 1.064 μm Q-switched Nd:YVO4 laser. When the repetition rate is set at 10 kHz, the maximum average total output power of 570 mW is achieved, including 410 mW of dual-signal radiations and 160 mW of dual-idler radiations. The total conversion efficiency is 32.5%. The tunable dual-signal wavelengths in the range of 1.474–1.518 μm and 1.490–1.539 μm and the dual-idler of 3.826–3.558 μm and 3.726–3.451 μm are obtained by changing the crystal temperature from 30°C to 200°C.

We demonstrate a 511 W laser diode pumped composite Nd:YAG ceramic laser. The optical pumping system is consisted of five laser diode stacked arrays arranged in a pentagonal shape around the ceramic rod whose size is Φ6.35×144 mm. When the pumping power is 1600 W, the cw laser output up to 511 W at 1064 nm can be obtained with a linear plano–plano cavity, and the optical-to-optical efficiency is 31.9%. To our knowledge, this is the highest value of laser output by using a newly invented composite Nd:YAG ceramic rod as the gain medium.

A pulsed nanosecond optical parametric generator (OPG) in periodically poled lithium niobate (PPLN) crystal is presented. The pump laser is an acousto-optically Q-switched Nd:YVO4 laser with the maximum average power of 6.58 W. When the repetition rate is 50 kHz and the pulse width of the pump source is 80 ns, the maximum average total output power of the single-pass PPLN OPG is about 1.9 W, which includes 1.322 W of 1.536 μm signal radiation. The length of the PPLN crystal is only 38.7 mm (at room temperature) with a grating period of 28.93 μm (at room temperature). The 1.502–1.536 μm signal radiation and 3.652–3.465 μm idler radiation are obtained by adjusting the PPLN crystal temperature from 155 degrees C to 250 degrees C.

NiO(70 nm)/NiFeCo(5 nm)/Cu(2 nm)/NiFeCo(5 nm) spin-valve multilayers were prepared by electron beam evaporation. It is found that the magnetoresistive (MR) ratio of the as-deposited films is relatively small (about 1.6%) and there is no apparent biasing in MR curves of as-deposited multilayers due to weak exchange coupling. Through heat treatment at a proper temperature in a magnetic field, the exchange field of the materials increases and the multilayers show good exchange-biased spin-valve MR character with MR value reaching about 2.5%. The proper temperature range for annealing is 200-250° C. With further increasing temperature, MR ratio drops rapidly.

Electroplated Cu, which can be compatible with integrated circuit technology and large-scale silicon wafers, is explored as a substrate to synthesize graphene domains by ambient-pressure chemical vapor deposition. Hexagonal single crystal domains of graphene are synthesized on electroplated Cu under dilute methane gas flow. Scanning electron microscopy images of graphene domains grown on electroplated Cu indicate that the domain size is time-dependent, and the domains can cross Cu grain boundaries and are distributed more uniformly on electroplated Cu surface than those grown on Cu foil.

We present an experimental method for in-situ observation of the lattice behavior of a single crystal silicon nanobelt during uniaxial tensile testing. An in-situ silicon nanobelt tensile testing device for transmission electron microscopy is developed. Atomic behavior and lattice parameters of the nanobelt are studied using selected area electron diffraction. A statistical and least square methods are used for reducing the measurement errors of the lattice parameters. The results suggest that the trends of the lattice parameters during the tensile test are in agreement with the increasing tensile stress in the silicon nanobelt. Furthermore, the local strain calculated from lattice parameters and the average strain of the nanobelt are compared.

A low-voltage-driven digital-droplet-transporting chip with an open structure is designed, fabricated and characterized. The digital microfluidic chip is fabricated by the silicon planar process. Using only a single electrode panel, the droplet on the chip can be manipulated by electrostatic force under a dc driving voltage. The actuation principle is proposed and verified by the experiment. The experimental results show that the minimum driving voltage decreases as the thickness of the dielectric layer decreases. The driving voltage for a 3 μL deionized (DI) water droplet is reduced to 15 V in air and 13.5 V in oil by employing a thin dielectric layer of 600 nm with a high dielectric constant and a coating hydrophobic layer on the top. The DI water droplets are also demonstrated to be transported in two dimensions smoothly in a programmable manner, and the maximum transport speed reaches 96 mm/s. The droplets of normal saline, a solution of 0.9 wt% NaCl, are also successfully manipulated on the chip.