Neural network applied to reconstruction of complex objects based on fringe projection

The neural network has been introduced into the reconstruction of the complex object based on fringe projection. In this method, the neural network with powerful property of approximation is used to get the continuous approximate function of a discrete fringe pattern captured by an image frame grabber. The depth-related phase of the measured object modulated into the fringe pattern can be demodulated by dealing with the approximate function. Compared with the Fourier transform profilometry (FTP), in the network method, one deformed fringe pattern is needed to reconstruct the tested object, and a high spatial resolution is maintained for no filtering process. Therefore, this method performs better than FTP in the measurement of the complex object. Moreover, the network method is capable of demodulating more depth-related phase even in the case that the local shadow exists in the fringe pattern. Computer simulations and experiments validate the feasibility of this method.     

Correlator-aided alignment of phase key in encrypted holographic storage systems

An encrypted holographic scheme with a compact alignment system for a phase key is proposed. Alignment for a phase key is performed by a holographic correlator. A filter in the correlator system contains the phase information used for encryption. Thus, it can be used to check the authorization of the phase key. Owing to the shift-invariant property of the holographic correlator, the location of the correlation peak is highly related to the alignment of the phase key. Therefore, the phase key can be repositioned on the desired location by searching for the specific position of the correlation peak. With the help of the correlator, alignment of the phase key can be done in 1 min. Experimental results using a correlator system in support of our proposed idea are demonstrated as well.     

Fast spin state initialization in a singly charged InAs-GaAs quantum dot by optical cooling

Quantum computation requires a continuous supply of rapidly initialized qubits for quantum error correction. Here, we demonstrate fast spin state initialization with near unity efficiency in a singly charged quantum dot by optically cooling an electron spin. The electron spin is successfully cooled from 5 to 0.06 K at a magnetic field of 0.88 T applied in Voigt geometry. The spin cooling rate is of order 10(9) s-1, which is set by the spontaneous decay rate of the excited state.     

大黄鱼肌肉中7种金属元素的原子吸收光谱分析

采用干法分解样品,应用火焰原子吸收光谱法测定了大黄鱼肌肉中、Ca、Cu、Zn、Fe、Mn、Cd、Pb的含量。研究了不同元素的仪器最佳工作条件、方法的准确度和精密度。在选定的实验条件下,大黄鱼中各元素间相互不干扰,可在同一份制备液中进行7种元素的分别测定。结果表明,大黄鱼肌肉中Ca、Cu、Zn、Fe和Mn含量分别为303.36、1.51、21.98、164.33、1.33μg/g,Cd、Pb未检出。方法加标回收率为93.9%—104.0%,相对标准偏差（n=8）为1.1%—2.5%,测定方法简单易行,方便快捷,结果可靠。     

Neutron depolarization study on the magnetic correlation length of nickel ferrite with different packing densities

The magnetic correlation length of a mixed nickel ferrite powder was studied by a newly commissioned depolarized neutron beamline at the W3 port of Tsing Hua Open Pool Reactor (THOR). In this work, Ni ferrite powder samples with different packing densities were studied. The magnetic correlation lengths of the sample were observed to be 2 μm at virgin state and about 3.1 μm at remanent state from the packing density of 20–60%. This magnetic domain size is smaller than particle size. No significant change of domain size at this packing density implies the domain wall motion is hindered by the porosity effectively up to at least 60% of packing density.     

与偏振无关双向2×2和4×4自由空间光开关

利用成熟的偏振控制技术,设计了一种由偏振光分束器、相位型空间光调制器和反射镜构成的2×2光开关,该光开关所用器件少,具有结构简单紧凑、控制灵活方便、功能实现与信号光的偏振态无关以及可以双向交换等特点;在此基础上通过2×2光开关的串连,设计了一种与偏振无关的双向4×4光开关的实验模块,根据其路由选择与控制方法,得到了4×4光开关实现信号光全排列无阻塞输出与交换对应的路由状态表,并对该实验模块的功能实现进行了详细的分析与讨论。     

Yb∶Y_3Al_5O_(12)晶体晶格振动光谱的研究

采用提拉法生长Y3Al5O12(YAG)晶体和Yb3 掺杂原子数分数分别为5%,10%,15%,20%,25%,50%和100%的Yb∶Y3Al5O12(Yb∶YAG)晶体。系统表征和分析了Yb3 掺杂浓度对拉曼光谱的影响。随着Yb3 掺杂浓度的增加,晶体的振动模式没有明显的变化,晶体结构没有改变;在370 cm-1和785 cm-1附近,振动吸收峰的半峰全宽逐渐增大。分析得出,Yb3 掺杂浓度对晶体的晶格、对称性、荧光寿命均有影响,从而可能影响到晶体的光谱和激光性能。     

LD抽运被动调Q固体激光器的脉冲稳定性

报道了二极管激光抽运Cr,Nd∶YAG被动调Q Nd∶YVO4 1064 nm激光输出.为了提高被动调Q激光的输出稳定性,谐振腔采用长腔,增益介质位于谐振腔中间位置.实验中获得了稳定的被动调Q激光输出.在最高入射抽运功率为17.5 W时,脉冲重复频率达到71.3 kHz,脉冲宽度为0.4 μs.调Q脉冲幅度不稳定性低于±10%,脉冲时间波动性低于±3.5%.