Shanghai Institute of Optics and Fine Mechanics,Chinese Academy of Sciences
Not a member yet
13355 research outputs found
Sort by
Improvement in medium long-term frequency stability of the integrating sphere cold atom clock
No full textNational High Technology Research and Development Program of China [2012AA120702]; Youth Innovation Promotion Association of the Chinese Academy of SciencesThe medium long-term frequency stability of the integrating sphere cold atom clock was improved. During the clock operation, Rb-87 atoms were cooled and manipulated using cooling light diffusely reflected by the inner surface of a microwave cavity in the clock. This light heated the cavity and caused a frequency drift from the resonant frequency of the cavity. Power fluctuations of the cooling light led to atomic density variations in the cavity's central area, which increased the clock frequency instability through the cavity pulling effect. We overcame these limitations with appropriate solutions. A frequency stability of 3.5 x 10(-15) was achieved when the integrating time tau increased to 2 x 10(4) s. (C) 2016 Optical Society of Americ
Research on Phase Modulation of Ramsey Fringes in Integrating Sphere Cold Atom Clocks
No full text在进行Ramsey作用时,以pi/2的相位差来调制同一频率点处两个周期微波脉冲,可以获得中心频率幅值为零的Ramsey条纹。这种方法可以直接通过中心频率处原子对探测光的吸收值变化来产生反馈本地振荡器的误差信号。理论上,相比于同相位Ramsey条纹,这种方法可以使得条纹信号幅值增加一倍。实验上,在积分球冷原子钟系统上,获得的相位调制Ramsey线型与理论计算相同,而且Ramsey条纹振荡幅值达到同相位下的1.6倍。国家高技术研究发展计划In the Ramsey scheme, if one modulates two microwave pulses at the same frequency but with pi/2 phase differences, the Ramsey fringes with zero amplitude at the central frequency can be obtained. By monitoring the variance of probe light absorption by atoms at the central frequency, one can get the error signals which feedbacks to the local oscillator. Theoretically, this method doubles the absorption signal intensity, compared with the case of Ramsey fringes with the same phase. Experimentally, the phase modulated Ramsey pattern in the integrating sphere cold atom clock system is the same with that from theoretical calculation. Moreover, the Ramsey fringe oscillation amplitude here is 1.6 times of that of Ramsey fringes with the same phase
Spectral Camera based on Ghost Imaging via Sparsity Constraints
No full textThe image information acquisition ability of a conventional camera is usually much lower than the Shannon Limit since it does not make use of the correlation between pixels of image data. Applying a random phase modulator to code the spectral images and combining with compressive sensing (CS) theory, a spectral camera based on true thermal light ghost imaging via sparsity constraints (GISC spectral camera) is proposed and demonstrated experimentally. GISC spectral camera can acquire the information at a rate significantly below the Nyquist rate, and the resolution of the cells in the three-dimensional (3D) spectral images data-cube can be achieved with a two-dimensional (2D) detector in a single exposure. For the first time, GISC spectral camera opens the way of approaching the Shannon Limit determined by Information Theory in optical imaging instruments
Study of above-threshold ionization by "Wigner-distribution-like function" method
No full text提出了一种类维格纳分布函数并用该分布函数计算了氢原子在少周期、不同偏振方向和不同激光频率的激光脉冲中电离后光电子的各种分布:线偏振下的时间-能量分布、时间电离率分布和椭圆偏振下的时间-出射角分布、角度分布和时间电离率分布.结果显示:随着激光频率降低,所有分布清楚直观地展现出电子从多光子区域到隧穿区域的转变过程.对线偏振情况,伴随着这种转变,电离时间与最终动量之间的半经典关系与时间-能量分布越来越一致.同时,时间-能量分布清楚地展现了隧穿区域中的干涉结构,并给出了干涉原因是由不同时刻电离出的具有相同能量的电National Basic Research Program of China [2013CB922201]; National Natural Science of Foundation of China [11304329, 11175227, 11105205, 11274050, 11334009, 11425414]; Shanghai Natural Science Foundation, China [13ZR1463100]A Wigner-distribution -like function is proposed to obtain various distributions of photoelectron emitted from H atoms in few-cycle laser pulses with different frequencies: time-energy distribution, time ionization distribution for linearly polarized laser field and time-emission angle distribution, angular distribution, and time ionization distribution for elliptically polarized laser field. With decreasing frequency, all the distributions clearly show a transition of ionization process from the multi-photon regime to the tunneling regime. For the case of linearly polarized laser pulse, accompanying this transition, the semiclassical relationship between the ionization moment and the final drift energy is becoming more and more close to the time-energy distribution. Meanwhile, the time-energy distribution clearly shows the interference structures in the tunneling regime, which can be attributed to the interference between the electrons with the same energy ejected at different times. For the case of elliptically polarized laser pulse, both the angular offset in the angular distribution and the time offset in the time ionization distribution are obtained by comparing the quantum calculation with the semi-classical result. The results show that the time offset is much smaller than the angular offset. This indicates that the "attoclock" technique which is based on the correspondence between two offsets is in principle inaccurate. Furthermore, the time offset can be both positive and negative. So this time offset cannot be interpreted as the tunneling time
Symmetric Matter Wave Splitting of Magnetically Insensitive States by Standing Wave Raman Light
No full text提出了基于磁不敏态的Raman-Nath对称分束方法和内态干涉方案。基于磁不敏态的干涉对磁场涨落敏感性较低,有助于增强干涉条纹的对比度。如果将Raman-Nath对称分束方法应用于路径共轭的原子陀螺仪,系统噪声可显著降低。通过优化双脉冲对称分束参数,可以获得较高的衍射效率。内态干涉方案成功解决了干涉动量态易受环境影响的问题。国家自然科学基金The method of Raman-Nath symmetric beam splitting based on magnetically insensitive states and the scheme of internal state interference are proposed.The interference based on magnetically insensitive states is insensitive to the magnetic fluctuation,which is beneficial to the contrast enhancement of interference fringes.If such a Raman-Nath symmetric beam splitting method is applied in the path-conjugate atom gyroscope,the system noise is obviously reduced.By means of optimizing the symmetric-beam-splitting parameters of double pulses,it is possible to obtain a high diffraction efficiency.The scheme of internal state interference is successfully used to solve the problem of momentum state interference being susceptible to the environment
Array illumination of a Fresnel-Dammann zone plate
No full textNational Natural Science Foundation of China (NSFC) [61205212, 61505228]The traditional Dammann grating is a phase-only modulation, and its theoretical foundation is based on far-field diffraction. Here we extend the traditional Fresnel zone plate (FZP) into a Fresnel-Dammann zone plate (FDZP), which is, in essence, considered as a FZP with Dammann modulation. Different from the Dammann grating, a single FDZP can generate array illumination from the near field to the far field by means of amplitude-only modulation in the absence of phase modulation. We then give some array illuminations operated in a water window to validate the feasibility and validity. This kind of wave-front modulation technology can be applied to array focusing and imaging from the x-ray to the EUV region. (C) 2016 Optical Society of Americ
Experimental Study on Amplified Spontaneous Emission in Large-Aperture Slab Amplifiers
No full text放大自发辐射(ASE)是影响钕玻璃大口径片状放大器增益性能的重要因素。通过测试钕玻璃大口径片状放大器在不同抽运条件下的增益性能,研究了ASE效应对增益系数和增益分布均匀性的影响,并利用实验数据推算出ASE效应造成的增益系数降低比例。随着抽运能量的增加,ASE效应造成的增益分布塌边、平均增益降低愈发明显。该研究为国产大口径钕玻璃片状放大器的优化设计提供了实验支撑。Amplified spontaneous emission(ASE)is a key issue which affects the gain of large-aperture Ndglass slab amplifiers.Gain measurement experiments under different pump conditions are carried out to study the effect of ASE on gain coefficients and gain distributions.The gain coefficient derating ratio caused by ASE is calculated based on the experimental data.The results show that the gain turning-down and the decrease of average gain becomes notable as the pump energy increases.The study provides experimental support for further optimization of homemade large-aperture slab amplifiers
Lens-free coherent modulation imaging with collimated illumination
No full textChinese Academy of Sciences, China [902012312D1100101]; [29201431151100301]We propose a lens-free coherent modulation imaging (CMI) method for reconstructing a general complex-valued wave field from a single frame of a diffraction pattern. A numerical Fourier transform is introduced in the iterative reconstruction process to replace the lens or zone plate used in the current CMI technique to adopt the constraint on the Fourier components of the exit wave field of the sample. While the complexity of the experimental setup is remarkably reduced by replacing the zone plate and additional accessories with the numerical processing, the energy fluence loss induced by the undesired diffraction orders of the zone plate can be also avoided. The feasibility of the proposed technique is verified experimentally with visible light
Online Detection of Airborne Molecular Contamination with Optical Microfiber and Quartz Crystal Microbalance
No full text为了监测高功率激光驱动器中有机污染物的挥发特性以及其在光学元件表面的沉积特性,研究了基于石英晶体微量天平和微纳光纤传感器的真空腔体内有机物在线监测技术.首先测试了不同分子态污染物浓度时石英晶体天平的响应性能,然后采用视角因子等分法对微纳光纤传感器和石英晶体天平进行对比实验,模拟有机污染物在光学表面沉积的特性.实验结果表明,石英晶体天平和微纳光纤测试有机物在光学表面沉积时响应一致,均可用于高功率激光驱动器有机污染物的在线监测;当污染物面密度大于0.5*10~(-5)g/cm~2时,微纳光纤传感器有较高精度和脉冲功率激光技术国家重点实验室开放研究基金In order to monitor the volatilization and deposition of organic contaminants on optics surfaces in high power laser facility, online detection of airborne molecular contaminant was investigated based on quartz crystal microbalance and optical microfiber. First, the response performance of quartz crystal microbalance for different densities of airborne molecular contamination was tested. Then the comparison of quartz crystal microbalance and optical microfiber in detecting the surface mass density of airborne molecular contamination was implemented with the view factor method. The characteristics of airborne molecular contamination deposited on optical surface were also studied. The experiment results show that quartz crystal microbalance and optical microfiber have the similar response performance, and thus they can be applied in online airborne molecular contamination detection. When the surface mass density of airborne molecular contamination is larger than 0.5*10~(-5)g/cm~2, optical microfiber is preferred due to the higher precision and larger response speed. The more the density of airborne molecular contamination is, the more it deposits on the optics
Two approaches to three-dimensional array foci of generalized Fibonacci structures
No full textNational Natural Science Foundation of China [61205212, 61505228]We propose two technologies to extend the number of layers in order to complete the three-dimensional (3D) array diffraction-limited foci, which means there are two-dimensional array foci at multi-focal planes. One technology is the diffractive optical lever; the other is multi-hybrid Fibonacci structures. Based on the aperiodic Fibonacci structures and binary phase modulation, various kinds of devices can be designed to produce 3D array foci whose focusing properties approximately satisfy the mathematical characteristics of the Fibonacci sequences. With those technologies, the diffraction-limited array foci are freely designed or distributed as required at the desired multiple focal planes