The effect of biaxial tensile strain on the thermal transport properties of MoS(2) is investigated by combining first-principles calculations and the Boltzmann transport equation. The thermal conductivities of single layer MoS(2) are found to be heavily suppressed by the applied strains; even a moderate biaxial tensile strain, 2 ∼ 4%, could result in a 10 ∼ 20% reduction in the thermal conductivity. Most interestingly, the reduction rate of thermal conductivity is size dependent,which is due to different dominant phonon scattering mechanisms at different sizes of MoS(2) samples. The sensitive strain dependence of thermal conductivity indicates that strain engineering could be an effective method to enhance the figure of merit for thermoelectric applications of MoS(2).

We present a novel method utilizing the χ(2) nonlinear optical technology, which can realize high precision measurement of linear electro-optic (EO) coefficients of nonlinear materials. By applying the linear EO effect to the nonlinear optical process, the theoretical model of this measurement method was established, and the calculation formula of the linear EO coefficient was given. In the proof-of-principle experiment, by introducing an external electric field into the fourth harmonic generation (FHG) process, we comprehensively obtained the linear EO coefficients of K(H1−xD x )2PO4 crystals and revealed the relationship between deuterium content (x) and EO coefficient (γ63): γ63 = −9.789 − 16.53x. Meanwhile, the stability of FHG was greatly improved, and the angular range of efficiency stability was increased to 4.4 times in maximum. This work not only systematically demonstrates the FHG characteristics of KDP-family crystals, which provides a good reference for the deep ultraviolet laser generation, but also offers a new way to measure the basic parameters of nonlinear optical materials.

No abstract

Compact, stable, high-power and high repetition rate picosecond laser systems are excellent sources for optical parametric chirped pulse amplification systems and laser satellite ranging systems. Compared with the traditional complex high-power amplifier, this article reports a compact high-power picosecond laser system at a repetition rate of 1 kHz based on Nd:YAG bulk crystal. The thermal lens effect limits the regenerative amplifier to directly output higher energy. For this reason, multi-stage traveling-wave amplifiers are usually used to gradually increase the laser pulse energy. So as to achieve a compact structure, a regenerative amplifier that can output higher power at 1 kHz is designed in the laser system. The regenerative amplifier can output the power of 6.5 W at the pump power of 41.5 W; the beam quality of M2 factor was about 1.3. A more flexible thermal depolarization compensation structure is applied in the side-pumped amplifier, which can effectively compensate for thermal lens effect and thermal depolarization at different pump powers. Finally, the laser pulse can achieve an output power higher than 50 W at 1 kHz after passing through an end-pumped traveling-wave amplifier and a side-pumped traveling wave amplifier.