Thyratron-based Pockels cell driver for single pulse switch-out in mode-locked lasers

A circuit is described which utilizes a hydrogen filled thyratron driven by a high current MOSFET as a high voltage (up to 12.5 kV), low jitter (0.2 ns) driver for a Pockels cell. Its use as a single pulse switch-out unit for a passively mode-locked Nd:YAG laser is demonstrated.     

Silicon Fabry-Perot interferometer as an optical FIR component: Application to variable couplers with uniform transmission of FIR optically-pumped lasers

The far-infrared characteristics of the double silicon etalon Fabry-Perot (FP) reflector are investigated. Measurements are reported at short FIR wavelengths. The low IR and FIR absorption and the high optimum reflectivity of this device allow convenient optimization of the coupling conditions of CW optically-pumped FIR lasers. Three sets of Si F. P. reflectors when chosen to cover complementary regions of the spectrum are adequate to cover between them most of the FIR range Using such a coupler respective output powers of 70 mW and 85 mW are obtained with the 70 m and 118 m CH₃OH lasers operating on the EH₁₁ mode for 16 W pump power injected in the FIR cavity. The variable reflector is also used to determine the unsaturated laser gain.Work supported by the Groupement de Recherches coordonnées du CNRS n^o 11 (Greco Micro ondes).     

HYSCORE and Davies ENDOR study of irradiated ultra high molecular weight polyethylene

Ultra high molecular weight polyethylene (UHMWPE) has been studied with different magnetic resonance techniques to elicit information on the nature and the location of radicals generated during high energy irradiation. Field swept electron paramagnetic resonance, pulsed Davies electron nuclear double resonance and hyperfine sublevel correlation spectroscopic measurements allowed extracting for the first time the full ¹H hyperfine coupling tensors of the most abundant radical, i.e. a secondary alkyl radical and to ascertain the formation of allyl radicals in the first stages of the irradiation process. The ¹H hyperfine coupling tensors are analogous to those reported for single crystal irradiated polyethylene, suggesting that radicals generated in UHMWPE are located in the crystalline region of the polymer. Copyright © 2012 John Wiley & Sons, Ltd.     

非线性偏振旋转中偏振控制器方位角的研究

提出一种基于Jones矩阵的非线性偏振旋转锁模光纤激光器数值模型, 对偏振控制器波片方位角的描述具有物理意义清晰的优点. 数值仿真得到均方根宽度为0.28 ps的超短脉冲, 时域对称且振幅稳定. 搭建了非线性偏振旋转锁模光纤激光器, 系统可以自启动, 得到了重复频率为67.35 MHz的锁模脉冲输出. 数值仿真和实验结果都表明偏振控制器两个波片的方位角α₁和α₂都具有周期性, 周期分别为180°和90°. 由于随机双折射的影响, 实验测得的波片方位角调谐范围比数值仿真的结果小, 这一点通过在数值仿真模型中加入随机双折射的作用而得到证明.     

Spectral dynamical behavior in two-section,quantum well,mode-locked laser at 1.064 μm

In this study, two-section mode-locked semiconductor lasers with different numbers of quantum wells and different types of waveguide structures are made. Their ultrashort pulse features are presented. The spectral dynamical behaviors in these lasers are studied in detail. In the simulation part, a two-band compressive-strained quantum well(QW) model is used to study thermally induced band-edge detuning in the amplifier and saturable absorber(SA). A sudden blue shift in laser spectrum is expected by calculating the peak of the net gain. In the experiment part, the sudden blue shift in the emission spectrum is observed in triple QW samples under certain operating conditions but remains absent in single QW samples.Experimental results reveal that blue shift phenomenon is connected with the difference between currents in two sections.Additionally, a threshold current ratio for blue-shift is also demonstrated.     

Interaction of parabolic-shaped pulse pair in a passively mode-locked Yb-doped fiber laser

We numerically investigate the formation and interaction of parabolic-shaped pulse pair in a passively mode-locked Yb-doped fiber laser. Based on a lumped model, the parabolic-shaped pulse pair is obtained by controlling the inter-cavity average dispersion and gain saturation energy, Moreover, pulse repulsive and attractive motion are also achieved with different pulse separations. Simulation results show that the phase shift plays an important role in pulse interaction, and the interaction is determined by the inter-cavity average dispersion and gain saturation energy, i.e., the strength of the interaction is proportional to the gain saturation energy, the stronger gain saturation energy will result in higher interaction intensity. On the contrary, the increase of the inter-cavity dispersion will counterbalance some interaction force. The results also show that the interaction of a parabolic-shaped pulse pair has a larger interaction distance compare to the conventional solitons.     

化学氧碘激光器非稳腔的研究

设计并研究了适合于连续波超音速化学氧碘激光器的正支共焦非稳腔，给出了放大率、输出功率和光束质量的实验结果。     

Third-order nonlinear optical properties of silver nanoparticles mediated by chitosan

Silver nanoparticles in chitosan medium were prepared by the chemical reduction method. Silver nitrate and hydrazine were used as the precursor and reducing agent in the present of chitosan as a natural host polymer. The samples are characterized by UV–visible spectroscopy, X-ray diffraction (XRD) and transmission electron microscopy (TEM). The measurements of nonlinear optical properties were defined by Z-scan technique using green CW laser beam operated at 532 nm wavelengths. Thermal effect has a dominant role in the overall material nonlinearity with CW laser. It is shown that the synthesized samples have a negative nonlinear refractive index.     

单模,单频连续1.3188μmNd：YAG激光器

报道了单模、单频连续１．３１８８μｍＮｄ：ＹＡＧ激光器的研制，测量了激光输出的方向性，稳定性，激光光谱及输出功率，对实验结果进行了理论分析。     

全光纤超短脉冲掺Yb3+光纤环形激光器

讨论了自启动被动锁模掺Yb³⁺光纤环形激光器产生短脉冲的机理，并研制出全光纤结构超短脉冲掺Yb³⁺光纤环形激光器.采用两个976nm半导体激光器级联抽运作为抽运源，高掺杂浓度掺Yb³⁺光纤作为增益介质，利用光纤的非线性偏振旋转效应，得到自启动、十分稳定的ps量级锁模光脉冲.激光器锁模阈值功率260mW，输出功率25mW，锁模光脉冲中心波长1056nm，3dB带宽11.7nm，重复频率20MHz.与其他结构光纤激光器相比，这种全光纤结构具有更高的效率和更好的稳定性. 关键词： 环形光纤激光器 3+光纤')" href="#">高掺杂浓度掺Yb³⁺光纤 自启动 被动锁模