1064 nm高功率明亮压缩态光场制备实验中绿光诱导红外吸收效应

通过实验和理论研究连续变量高功率明亮压缩态光场制备实验中高功率种子光注入光学参量放大器引起的绿光诱导红外吸收效应。首先,通过优化实验系统工作参数,提升反馈控制回路的锁定稳定性,当种子光功率为500 mW、泵浦光功率为145 mW时,在分析频率为3 MHz处,获得光功率为200μW、压缩度为(-10.7±0.2) dB的明亮压缩态光场。然后,根据实验数据,定量分析高功率明亮压缩态光场与压缩真空态光场产生过程中周期极化磷酸氧钛钾晶体的吸收损耗,发现高功率明亮压缩态光场实验系统的总光学损耗为(9±0.05)%,其中由周期极化磷酸氧钛钾晶体吸收导致的内腔损耗为(5.8±0.05)%,占总光学损耗的(64.4±0.05)%。该条件下周期极化磷酸氧钛钾晶体对高功率明亮压缩态光场的吸收系数为(6.0±0.05)×10^-2 cm^-1。当泵浦光单独注入光学参量放大器时,周期极化磷酸氧钛钾晶体对压缩真空态光场的吸收系数约为2.1×10^-4 cm^-1。由此可知,当高功率种子光注入光学参量放大器时,绿光诱导红外吸收效应使周...     

The abnormal lattice contraction of plutonium hydrides studied by first-principles calculations

Pu can be loaded with H forming complicated continuous solid solutions and compounds,and causing remarkable electronic and structural changes.Full potential linearized augmented plane wave methods combined with Hubbard parameter U and the spin-orbit effects are employed to investigate the electronic and structural properties of stoichiometric and non-stoichiometric face-centered cubic Pu hydrides(PuHx,x=2,2.25,2.5,2.75,3).The decreasing trend with increasing x of the calculated lattice parameters is in reasonable agreement with the experimental findings.A comparative analysis of the electronic-structure results for a series of PuH x compositions reveals that the lattice contraction results from the associated effects of the enhanced chemical bonding and the size effects involving the interstitial atoms.We find that the size effects are the driving force for the abnormal lattice contraction.     

1064 nm高功率明亮压缩态光场实验制备中的热透镜效应

本文通过理论和实验分析了1064 nm高功率明亮压缩态光场实验制备过程中,高功率种子光和泵浦光注入光学参量放大器引起的热透镜效应和模式失配。首先根据热透镜理论模型,定量分析了高功率种子光和泵浦光注入光学参量放大器时,周期极化磷酸氧钛钾晶体内部热透镜的等效焦距。然后根据高斯光束与光学谐振腔的模式匹配理论模型,理论分析了高功率种子光和泵浦光与光学参量放大器的模式失配量。最后在高功率明亮压缩态光场正常输出的工作状态下,重新优化种子光和泵浦光与光学参量放大器的模式匹配效率,在种子光功率为500 mW、泵浦光功率为145 mW的条件下,在分析频率3 MHz处,直接测得光功率为200μW、压缩度为-10.8 dB±0.2 dB的明亮压缩态光场。上述实验结果与有关文献测得的压缩度仅相差0.1 dB,表明在本文实验系统中,高功率种子光和泵浦光引起的热透镜效应对光学参量放大器输出明亮压缩态光场的压缩度基本没有影响。     

Structural, magnetic, electronic, and elastic properties of face-centered cubic PuHx （x=2, 3） ： GGA （LSDA） ＋ U ＋ SO

We perform first-principles calculations to investigate the structural, magnetic, electronic, and mechanical properties of face-centered cubic (fcc) PuH 2 and fcc PuH 3 using the full potential linearized augmented plane wave method (FP-LAPW) with the generalized gradient approximation (GGA) and the local spin density approximation (LSDA) taking account of both relativistic and strong correlation effects. The optimized lattice constant a0 = 5.371  for fcc PuH2 and a0 = 5.343  for fcc PuH3 calculated in the GGA + sp (spin polarization) + U (Hubbard parameter) + SO (spin-orbit coupling) scheme are in good agreement with the experimental data. The ground state of fcc PuH3 is found to be slightly ferromagnetic. Our results indicate that fcc PuH2 is a metal while fcc PuH3 is a semiconductor with a band gap about 0.35 eV. We note that the SO and the strong correlation between localized Pu 5f electrons are responsible for the band gap of fcc PuH3 . The bonds for PuH2 have mainly covalent character while there are covalent bonds in addition to apparent ionicity bonds for PuH3 . We also predict the elastic constants of fcc PuH2 and fcc PuH3 , which were not observed in the previous experiments.     

Abnormal lattice contraction of plutonium hydrides studied by first-principles calculations

Pu can be loaded with H forming complicated continuous solid solutions and compounds, and causing remarkable electronic and structural changes. Full potential linearized augmented plane wave methods combining with Hubbard parameter U and the spin-orbit effects are employed to investigate the electronic and structural properties of stoichiometric and non-stoichiometric face-centered cubic Pu hydrides (PuH_x, x=2, 2.25, 2.5, 2.75, 3). The decreasing trend with increasing x of the calculated lattice parameters is in reasonable agreement with the experimental findings. A comparative analysis of the electronic-structure results for a series of PuH_x compositions reveals that the lattice contraction is resulted from the associated effects of the enhanced chemical bonding and the size effects involving the interstitial atoms. We find that the size effects are the driving force for the abnormal lattice contraction.