基于微光机电系统的微光学自适应微镜的研究

提出了一种利用热应力改变镜面曲率的可调焦微光学自适应微镜。与传统自适应微镜相比,采用该原理制作的微镜具有驱动电压低和驱动力较大的优点,而且制作简单。以硅为基底进行了表面热氧化、光刻显影、HF酸刻蚀、KOH湿法刻蚀,溅射铝膜等微加工工艺的研究,获得硅铝双金属可调焦微反射镜4×4阵列,单元尺寸3 mm×3 mm,单晶硅基底厚60μm,硅表面溅射的铝膜厚150 nm。该微镜的镜面填充率为100%,可变形镜面占总镜面面积的79%。利用激光波面干涉仪对可调焦微反射镜的动态性能进行了测试。实验表明,该微镜可产生单向连续变形,最大变形量15.8μm,非线性滞后27%,工作电压0~2.5V,可调焦范围∞~0.036 m。     

Working group report: Flavor physics and model building

This is the report of flavor physics and model building working group at WHEPP-9. While activites in flavor physics have been mainly focused on B-physics, those in model building have been primarily devoted to neutrino physics. We present summary of working group discussions carried out during the workshop in the above fields, and also briefly review the progress made in some projects subsequently.     

Efficient and wavelength-tunable anti-Stokes frequency conversion with good beam quality in the fundamental mode of photonic crystal fiber

Using the photonic crystal fiber (PCF) with the zero dispersion wavelength of 848 nm for the fundamental mode, the efficient anti-Stokes signal generations from 645 to 543 nm are realized by pumping in the normal dispersion region. When the pump average power increases from 200 to 500 mW, the output power of the anti-Stokes signal increases 8.46 times, the power ratio of the anti-Stokes signal at 543 nm to the residual pump is calculated as 22.6:1, and the conversion efficiency η in the experiment can be up to 46%. Moreover, good optical beam quality of the anti-Stokes signal can be achieved.     

Separate spatial soliton pairs in a biased series centrosymmetric photorefractive crystal circuit

It is shown theoretically that three types of separate soliton pairs: bright-bright, bright-dark, and dark-dark, can be established in a biased series circuit consisting of two centrosymmetric photorefractive crystals and the two solitons in a separate soliton pair can affect each other by the light-induced current. The effects of the intensities of soliton beams and background lights on the normalized profiles of solitons are discussed.     

High power passively mode-locked Nd:YVO<Subscript>4</Subscript> laser using graphene oxide as a saturable absorber

We report on a passively mode-locked Nd:YVO₄ laser using a novel graphene oxide saturable absorber fabricated by vertical evaporation method. An 880 nm LD pump source was used to reduce the thermal load of the laser crystal. At the pump power of 7.4 W, 1.2 W average output power of continuous wave mode-locked laser with optical conversion efficiency of 16.2% was achieved. To the best of our knowledge, this is the highest output power of passively mode-locked solid-state laser using graphene oxide saturable absorber. The repetition rate of passively mode-locked pulse was 88 MHz with the pulse energy of 13.6 nJ.     

Influence of maglev force relaxation on the forces of bulk HTSC subjected to different lateral displacements above the NdFeB guideway

This paper studied the influence of maglev force relaxation on the force (both levitation and guidance forces) of bulk high-temperature superconductor (HTSC) subjected to different lateral displacements above a NdFeB guideway. Firstly, the maglev forces relaxation property of bulk HTSC above the permanent-magnet guideway (PMG) was studied experimentally, then the levitation and guidance forces were measured by SCML-2 measurement system synchronously at different lateral displacements, some times later(after relaxation), the forces were measured again as the same way. Compared to the two measured results, it was found that the change of the levitation force was larger compared to the case without relaxation, while the change of the guidance force was smaller. In addition, the rate of change of levitation force and guidance force was different for different maximum lateral displacements. This work provided a scientific analysis for the practical application of the bulk HTS.     

基于搜索平均法的气象观测数据的非线性去噪

介绍了一种新型基于相空间重构和返回图法的非线性降噪方法——搜索平均法，首先将该方法应用于被高斯白噪声所污染的Henon映射时间序列，说明根据降噪理论所编写的计算程序的正确性；然后应用于中国气象局公布全国435站1960—2000年的逐日气温观测时间序列，并利用非线性预报方法衡量降噪的效果，验证了该方法的有效性.     

MgF2单晶的THz光谱研究

利用THz时域光谱技术对MgF₂晶体(样品1)和MgF₂：Co晶体(样品2)在0.5—2.5 THz的吸收特性进行了研究.在0.5—2.5 THz波段，样品1吸收系数α(ν)随频率ν增加而增大，最大值为24 cm^-1.样品2的吸收系数比样品1大得多，Co掺杂使晶格吸收带边向低频移动，而且样品2在1.9 THz有吸收峰，吸收系数达到70 cm^-1，由此求出F^--Co²⁺离子键伸缩振动的键力常数K为3.40×10^-2　N/cm.这一结果表明，THz光谱分析有可能成为研究晶体化学键的一种重要手段.利用光学常数之间的关系计算了两个样品在0.5—2.5 THz的介电函数的实部ε₁(ν)，得到样品1的ε₁(ν)值在4.67至4.73之间，样品2的ε₁(ν)值在4.62至5.01之间. 关键词： THz辐射 光谱 2晶体')" href="#">MgF₂晶体     

Be(d,n)反应中子源能谱测量及应用

 利用中子飞行时间技术和BC501A液体闪烁探测器的粒子分辨特性,测量了0°方向、20 MeV氘束轰击厚金属铍靶反应产生的中子源能谱,测量的中子能谱范围为0.7～25.0 MeV。在60°方向放置芪晶体闪烁探测器,由刻度好的BC501A液体闪烁探测器归一校正后,用于中子源强度监测。利用Be(d, n) 反应中子源,采用单粒子灵敏度标定方法,实验标定了0.75~15.75 MeV能量范围内的薄膜闪烁探测器中子能量响应曲线,实验结果与蒙特卡罗模拟计算结果在8%的不确定度范围内一致。     

Optical parametric chirped pulse amplification based on photonic crystal fibre

A compact two-stage optical parametric chirped pulse amplifier based on photonic crystal fibre is demonstrated.A 1064-nm soliton pulse is obtained in a home-made photonic crystal fibre (PCF) with femtosecond pulse pumping and then amplified to 2 mJ in an Nd:YAG regenerative amplifier.After the amplified pulses pass through the LBO crystal,the 532-nm double-frequency light with an energy of 0.8 mJ and a duration of over 100 ps at 10-Hz repetition rate is generated as a pump source in the following two-stage optical parametric amplification (OPA).The 850-nm chirped signal light gain from the stretcher is 1.5×10 4 in the first-stage OPA while it is 120 in the second-stage OPA.The total signal gain of optical parametric chirped pulse amplification (OPCPA) can reach 1.8×10 6.