Enhancement of coercivity with reduced grain size in CoCrPt film grown by pulsed laser deposition

We report a pulsed laser deposition (PLD) growth of VMn/CoCrPt bilayer with a magnetic coercivity (H_c) of 2.2 kOe and a grain size of 12 nm. The effects of VMn underlayer on magnetic properties of CoCrPt layer were studied. The coercivity, H_c, and squareness, S, of VMn/CoCrPt bilayer, is dependent on the thickness of VMn. The grain size of the CoCrPt film can also be modified by laser parameters. High laser fluence used for CoCrPt deposition produces a smaller grain size. Enhanced H_c and reduced grain size in VMn/CoCrPt is explained by more pronounced surface phase segregation during deposition at high laser fluence.     

空间外差干涉光谱仪仪器线型函数测量新方法研究

空间外差干涉光谱技术是近年发展起来的新型静态超分辨光谱分光技术, 仪器线型函数是其基本性能参数之一, 代表了仪器的光谱分辨能力, 需要精确表征。在分析仪器线型函数影响因素(切趾、有效视场角与离轴像元效应)以及测量方法与测量光源等特殊性要求基础上, 提出了一种可调波长单色面光源的全新测量方法, 并利用可调谐激光器与消散斑积分球等设备搭建了测量实验装置。在仪器线型函数测量实验中, 通过选取光谱范围内的典型谱段进行高光谱(0.1 nm步长)扫描, 经过干涉数据误差修正、光谱复原以及坐标归一化等数据处理过程, 获取了仪器线型函数的能量分布形式。此外, 利用全光谱范围内扫描的干涉数据, 得到仪器线型函数的全峰半宽随波长的变化规律曲线。最后, 将本方法获取的实测仪器线型函数与模拟光谱(LBL计算)进行卷积获取理论谱, 并与地基探测实验获取的实测大气CO2吸收光谱进行比对分析, 两者吻合一致, 验证了本方法获取的仪器线型函数具有较高的精度。     

On‐chip stimulated Brillouin Scattering for microwave signal processing and generation

Demonstration of continuously tunable delay, low‐noise lasers, dynamically controlled gratings, and optical phase shifting using the stimulated Brillouin scattering (SBS) process has lead to the emergence of SBS as a promising technology for microwave photonics. On‐chip realization of SBS enables photonic integration of microwave photonic signal processing and offers significantly enhanced performance and improved efficiency. On‐chip stimulated Brillouin scattering is reviewed in the context of slow‐light based tunable delay, low‐noise narrow linewidth lasers and filtering for integrated microwave photonics. A discussion on key material and device properties, necessary to enable on‐chip Brillouin scattering using both the single‐pass and resonator geometry, is presented along with an outlook for photonic integration of microwave signal processing and generation in other platforms.     

Intracavity phase interferometry: frequency combs sensor inside a laser cavity

In traditional interferometric measurements, a physical quantity that changes the phase of a resonator is monitored through a change of its transmission. Interferometry inside a laser exploits the ultimate Q‐factor of that resonator, and converts the phase to be measured into a frequency. A mode‐locked laser with two intracavity pulses emits two frequency combs of the same repetition rate. The quantity to be measured (a sub‐nano displacement, a nonlinear index, an acceleration or rotation, a magnetic or electric field) produces a minute phase change ( rad) in one of the two intracavity pulses, which is converted into a frequency, measured by beating the two pulse trains emitted by the laser. This paper presents methods of operating mode‐locked lasers in which two independent pulses circulate, producing two frequency combs of the same repetition rate. Various examples of physical quantities that can be measured through this technique are presented.     

用零输出的设备探测引力波

理论估计传到地球上的引力波非常弱,激光干涉引力波探测器被设计用来探测引力波,在没有引力波传来时,激光干涉引力波探测器应该是零输出。为达到这样的目的,必须和众多的噪声作斗争。     

Laser produced plasma: A pumping source for cadmium photo-ionization laser

We report laser oscillations in Cd II on 4d ⁹5s ^{2 2} D _5/2 − 4d ¹⁰5p ² P _3/2 transition at 441.6 nm using laser produced tungsten plasma as a pumping source. Mach Zehnder interferometer is used to measure electron density. Design and working of the crossed heat pipe used in the studies is discussed.     

Amplified low-repetition-rate fs pulsewidth measuring and DLA caused pulse broadening

Amplified low-repetition-rate fs pulse is generated with dye laser amplifier(DLA). The pulsewidth is measured with a computer-aided autocorrelator and the fs pulsewidth broadening caused by the dispersion of the DLA is analyzed. Furthermore, the autocorrelator introduced in this paper could be used as a low scanning autocorrelator to measure high-repetition-rate pulsewidth.     

光纤激光器的偏振开关操作

本文阐述了采用光子注入法实现光纤激光器的偏振开关操作.这种新颖的全光开关器件具有极低的阈值(0.1μW).对操作机理、实验实现和器件特性.     

纯热传导冷却产生软X射线激光

本文通过n_e=1×10~(19)cm~(-3)的热等离子体,在纯热传导冷却机制下的计算,得到了等离子体温度的时空变化,并运用碰撞-辐射模型计算了在这种条件下,类锂铝离子4f-3d,5f-3d跃迁的增益系数,计算表明:只要有合适的初始条件,用纯热传导冷却机制,也能产生软X射线激光增益.     

带超环面镜的掠入射光栅谱仪测试系统响应特性模拟分析

指出了文献[1]在物理概念上和公式推导中的错误,并在订正了这些错误之后,考虑了实际的激光等离子体光源的几何尺度和线状等离子体的安排,对在复合泵浦X激光增益实验中所使用的带超环面镜X光中继元件的掠入射光栅光谱仪系统进行了全面的模拟计算.结果表明,作者所使用的带超环面镜的X光增益测试系统,其因离焦而导致的非线性效应是完全可以忽略的,系统的空间分辨能力的下降也是非常小的,从而否定了文献[1]中的结论,表明作者在X激光增益测量实验中所使用的带超环面镜X光中继元件的掠入射光栅光谱仪系统是完全可靠的.