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p-Si/Si0.5Ge0.5 superlattices (SLs) grown on a vicinal-cut p-type silicon single crystalline substrate by molecular beam epitaxy (MBE) were irradiated by a KrF excimer laser. Two types of transient laser induced voltage (LIV) signals were observed, among which the signals of 0.3 V in amplitude with time response ∼40 ns showed up along the tilted directions, while voltage signals of ∼10 mV with a time response of tens of microseconds presented along the untilted directions which were perpendicular to the tilted direction. The results demonstrate that the observed photoelectric signals of 0.3V amplitude are laser induced thermoelectric voltages (LITV) due to the tilting angle relation. The observed LIV signals implied that these SLs exhibited anisotropic Seebeck components. It was also found that the LIV signals increased with the p-type doping level in the Si layer, which was coincident with the expectation of the laser induced thermoelectric effect. According to the measured signals and the theoretical formula, one can calculate the physical parameters of the SLs. The calculated effective Seebeck anisotropy coefficients (Sab − Sc) for samples with 1018 cm−3 and 1020 cm−3 are approximately 11.2 µV K−1 and 18.2 µV K−1, respectively.

Laser pulse durations are dominated by the spectral bandwidths in chirped pulse amplification systems.Therefore,gain narrowing during amplification is one of the most important factors that limits the minimal pulse durations of compressed pulses in high_power ultrashort_pulse laser systems.The gain narrowing can be compensated by applying an acousto_optic programmable dispersive filter(AOPDF) to the laser system.Here we present the experiments and results with an AOPDF for the 200_TW Ti:sapphire laser.The spectral bandwidth is increased from the original 27?nm to 44?nm.The pulse duration correspondingly is decreased from 60?fs to 30?fs and thus the output pulse power is doubled.

The multiferroic material is one the hot spots in the materials research area which can be widely used in many new functional devices. Barium titanate (BaTiO3, BTO) has attracted many interests for its multiferroic properties because of its exotic physical properties, such as ferroelectricity, high dielectric constant and electro-optical properties at room temperature. The BaTi0.94(TM1/2Nb1/2)0.06O3 (TM=Mn/Ni/Co) ceramic samples were prepared by solid state reaction method and the structure, electrical, magnetic and optical properties were systematically studied. The crystal structure of all doped samples changes from tetragonal to cubic phase without any hexagonal phase depending on ionic radius. The weakening of Raman scattering peaks of BTO tetragonal phase further proves the phase transition to cubic phase caused by doping. The Curie temperature (TC) has a dramatic decrease with the dopant as the phase transition from the tetragonal phase to the cubic phase.Although the ferroelectricity is weakened, it is still remained. The magnetic measurement suggests show that Ni-Nb doped sample has the strongest ferromagnetism among different dopants which can be deduced by the F-center exchange (FCE) theory. Furthermore, the energy gaps of BaTi0.94(TM1/2Nb1/2)0.06O3 are obviously reduced compared to that of BTO, which can be reasonably explained by impurity level and band theory. These results indicate that BTO based multiferroic ceramics with ferroelectric and ferromagnetic coexisting at room temperature can be obtained by B-site co-doping, which can be expected to be widely used in multiferroic functional devices.