R. X. Li
Chinese Academy of Sciences
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Featured researches published by R. X. Li.
Applied Physics Letters | 2006
Tianqing Jia; F. L. Zhao; Min Huang; Hongxin Chen; Jie Qiu; R. X. Li; Z. Z. Xu; H. Kuroda
Nanoripples with periods of 150 and 80 nm are formed on the surface of 6H-SiC crystals irradiated by the p-polarized 800 nm and the s-polarized 400 nm femtosecond lasers, respectively. When both of the two collinear laser beams focus simultaneously on the sample surface, nanoparticles are formed on the whole ablation area, and they array in parallel lines. We propose and confirm that the second harmonics in the sample surface excited by the incident lasers plays an important role in the formation of nanostructures.
Applied Physics Letters | 2003
Tingting Jia; Z. Z. Xu; Xiuzhi Li; R. X. Li; B. Shuai; F. L. Zhao
We report measurements of damage threshold and ablation depth for SiO2 and CaF2 irradiated under lasers at wavelengths of 800 and 400 nm for duration of 45–800 fs. These results can be well understood by using a developed avalanche model. The model includes the production of conduction band electrons (CBEs), laser energy deposition, and CBE diffusion. The evolution of microexplosion is investigated based on this model.
Applied Physics Letters | 2006
Tianqing Jia; Hongxin Chen; Min Huang; X.J. Wu; F. L. Zhao; Motoyoshi Baba; M. Suzuki; H. Kuroda; Jie Qiu; R. X. Li; Z. Z. Xu
Uniform ZnSe nanowires are observed on the ablation crater on ZnSe crystal surface irradiated by femtosecond lasers in air, while other parts of the sample surface are not polluted. The nanowire growth rate is about 5μm∕s, it is higher than that fabricated by chemical vapor deposition method by a factor of 104. The nanowire length and diameter can be controlled by varying laser pulse energy and pulse number. The formation mechanism is studied and found to be self-catalyzed vapor-liquid-solid process.
Journal of Applied Physics | 2012
G. Bai; R. X. Li; Z. G. Liu; Yidong Xia; J. Yin
Using the phenomenological Landau thermodynamic theory, we have investigated the effect of external mechanical loads on the phase transition and physical properties of poly(vinylidene fluoride-trifluorethylene) [P(VDF-TrFE)] thin films. Quantitative calculation shows that the phase transition temperature, polarization, dielectric, pyroelectric, and piezoelectric properties are highly sensitive to external mechanical loads. External compressive stress increases the phase transition temperature and the out-of-plane polarization and decreases the out-of-plane dielectric constant below Tc, pyroelectric coefficient, and piezoelectric coefficient (absolute value) and vice versa. Compared with pervoskite-type ferroelectrics, the calculated results are opposite due to the different intrinsic parameters between pervoskite and polymer ferroelectrics, especially, electrostrictive constants. The ability to tailor the properties in ferroelectric P(VDF-TrFE) thin films with the mechanical load can offer a tremendously ...
Physics of Plasmas | 2015
Haiying Zhang; B. Shen; Wenpeng Wang; Yonggang Xu; Yaoxiang Liu; Xiaoyan Liang; Ying Leng; R. X. Li; Xueqing Yan; Jun Chen; Z. Z. Xu
We present experimental studies on ion acceleration from diamond-like carbon (DLC) foils irradiated by 800 nm, linearly polarized laser pulses with peak intensity of 1.7 × 1019 W/cm2 to 3.5 × 1019 W/cm2 at oblique incidence. Diamond-like carbon foils are heated by the prepulse of a high-contrast laser pulse and expand to form plasmas of near-critical density caused by thermal effect before the arrival of the main pulse. It is demonstrated that carbon ions are accelerated by a collisionless shock wave in slightly overdense plasma excited by forward-moving hot electrons generated by the main pulse.
Applied Physics Letters | 2012
Wenpeng Wang; H.F. Zhang; B. Wu (伍波); C. Y. Jiao ( 焦春晔 ); B. Zhu (朱斌); Kegong Dong; W. Hong (洪伟); Y. Q. Gu; Baifei Shen; Yi Xu; Ying Leng; R. X. Li; Z. Z. Xu
Megaelectronvolt (MeV) ion beams with low divergence (10 Degree-Sign ) are experimentally generated from a thin foil irradiated by an ultrahigh-contrast laser at a peak intensity of {approx}10{sup 18} W/cm{sup 2}. The high-contrast ({approx}10{sup 11}) laser is obtained with a pulse cleaner based on noncollinear optical-parametric amplification and second-harmonic generation processes. The effects of the foil density, foil thickness, as well as the density gradients at the front and back sides of the foil are investigated with two-dimensional particle-in-cell simulations. The beam parameters of maximum energy and divergence strongly depend on the density gradients at the back side of the foil.
Applied Physics Letters | 2013
Wenpeng Wang; Baifei Shen; H.F. Zhang; Yongbing Xu; Youyong Li; Xinhui Lu; C. Wang; Yaoxiang Liu; J. X. Lu; Y. Shi; Ying Leng; Xue-Jin Liang; R. X. Li; Ning Wang; Z. Z. Xu
A pulse cleaner based on noncollinear optical-parametric amplification and second-harmonic generation processes is used to improve the contrast of a laser of peak intensity ∼2 × 1019 W/cm2 to ∼1011 at 100 ps before the peak of the main pulse. A 7 MeV proton beam is observed when a 2.5 μm-thick Al foil is irradiated by this high-contrast laser. The maximum proton energy decreases to 2.9 MeV when a low-contrast (∼108) laser is used. Two-dimensional particle-in-cell simulations combined with MULTI simulations show that the maximum proton energy sensitively relies on the detecting direction. The ns-time-scale prepulse can bend a thin target before the main pulse arrives, which reduces maximum proton energy in the target normal sheath acceleration.
Laser Physics Letters | 2013
Y X Chu; Xiaoyan Liang; L H Yu; Lu Xu; Xiaoming Lu; Yanqi Liu; Ying Leng; R. X. Li; Z. Z. Xu
Theoretical and experimental investigations are carried out to determine the influence of the time delay between the input seed pulse and pump pulses on transverse parasitic lasing in a Ti:sapphire amplifier with a diameter of 80?mm, which is clad by a refractive index-matched liquid doped with an absorber. When the time delay is optimized, a maximum output energy of 50.8?J is achieved at a pump energy of 105?J, which corresponds to a conversion efficiency of 47.5%. Based on the existing compressor, the laser system achieves a peak power of 1.26?PW with a 29.0?fs pulse duration.
Applied Surface Science | 2002
Tingting Jia; R. X. Li; Zongshun Liu; Hao Chen; Z. Z. Xu
The one- and the two-photon absorption rates of conduction-band electrons (CBEs) in dielectric materials are calculated by second- and third-order perturbation theory, respectively. Here fused silica irradiated under 526 nm ultra-short pulse laser is used as an example. Compared with the case that only the one-photon absorption of CBE assisted by a phonon is considered, the rate of total energy gain of CBE from laser field will be enhanced by a factor of 3 when both of the one- and the two-photon absorption are included. The avalanche rate includes not only the term proportional to laser intensity, but also the terms proportional to the square of laser intensity and to the product of laser intensity and hole density. The damage threshold is calculated on the basis of the avalanche model, and find it is lowered by about 15% compared with the case for only the one-photon absorption of CBE assisted by a phonon is considered. The theoretical value agrees well with experimental results.
Laser Physics Letters | 2013
Yanyan Li; Yansui Huang; J Z Wang; Yi Xu; Xiaoming Lu; Dong Wang; Yuxin Leng; R. X. Li; Zhizhan Xu
We demonstrate a carrier-envelope phase (CEP) stabilized high temporal contrast generator at 1053 nm for the first time. The device relies on a collinear optical parametric amplifier (OPA) followed by a frequency-doubling crystal. It is driven by a femtosecond laser source centered at 800 nm and finally generates CEP passively stabilized pulses with an energy of 130 μJ and a FWHM for the spectrum of 40 nm with 46 fs pulse duration at 1053 nm. The temporal contrast reaches >1011 at a few picoseconds before the main pulse.