Nulling interferometry by use of geometric phase

Nulling interferometry is a method of detecting a faint source near a bright one, in which destructive interference is realized for the light from the bright source. A nulling interferometer that makes use of geometric phase (Pancharatnam phase) is proposed. An experimental setup is constructed to simulate a stellar interferometer with geometric-phase modulation. We attained extinction of 6 x 10(-5) in white light.     

The ulysses space mission

Summary We describe briefly the collaborative ESA-NASA Ulysses mission which will provide, for the first time in the history of the Solar-System exploration,in situ observations of the heliosphere over a broad range of heliographic latitudes. Launched on October 6, 1990, Ulysses has been injected in a high-inclination orbit by means of a gravity-assisted manoeuvre at the time of his encounter with Jupiter, in February 1992. On-board instrumentation will obtain data on the solar wind, the heliospheric magnetic field, radio, X-and γ-bursts plasma waves and interplanetary and interstellar gas and dust. Italy participates to the mission with an experiment, led by Professor Bruno Bertotti, of the University of Pavia, aimed at detecting gravitational waves, and with an interdisciplinary investigation, led by Professor Giancarlo Noci, of the University of Florence, where scientists from the University of Florence, the Arcetri Astrophysical Observatory, the Institute for the Physics of the Interplanetary Space of Frascati and the Observatory of Trieste will use data from different experiments to study the dependence of mass loss, ion composition and turbulence of the solar wind on heliographic latitude. Paper presented at the V Cosmic Physics National Conference, S. Miniato, November 27–30, 1990.     

飞向地球核心

美国加州理工学院的DavidStevenson教授在最近提出了一项重要的建议 ,他主张进行一项向地球核心飞行的空间计划 ,他认为这是一件值得科学家们考虑的空间工程 .这个空间内填充的不是普通的真空 ,而是坚硬的岩石 ;同时它的“空间飞船”也不是通常的飞行工具 ,而是类似于葡萄柚大小的地震波探测器 .研究工作将按如下的步骤进行 :一个带有爆炸装置的探头将沿着地球表面的裂缝向下滑落并发生引爆 .然后把一个装满熔化铁水的探测器注入裂缝内 ,由于地球重力的作用 ,裂缝将以每秒 5m的速度向下延伸 ,直到其封堵为止 .这些地球内部的裂缝将会有规则…     

The ACES/PHARAO space mission

Proposed in 1997, the ACES/PHARAO experiment is a space mission in fundamental physics with two atomic clocks on the International Space Station, a network of ultra-stable clocks on the ground, and space-to-ground time transfer systems. The ACES flight instruments are near completion and launch in space is planned for the first half of 2017 for a mission duration of three years. A key element of the satellite payload is a cold-atom clock designed for microgravity environment, PHARAO, operating with laser-cooled cesium atoms. Here we first report on the design and tests of the PHARAO flight model, which is now completed and ready for launch. We then briefly present the status of development of the other instruments of the ACES payload, the Space Hydrogen Maser, the microwave time-transfer system (MWL), and the laser time transfer ELT.     

Limitations of atom interferometry for gravitational wave observations in space

A paper published recently (Hogan et al. in Gen. Relativ. Gravit. 43:1953–2009, 2011) suggests the use of atom interferometry between satellites in Earth orbit to observe gravitational waves. The proposed altitude and satellite separation are about 1,000 and 30 km respectively. The difference in acceleration between clouds of ultracold atoms in atom interferometers near the two satellites would be detected by using laser beams between the interferometers. Because of the measurement path being very short compared with the million km or longer measurement path for a proposed laser interferometer gravitational wave antenna in space, the sensitivity to differential fluctuations in the laser phase as seen by the atoms in the two atom interferometers is very high. Problems introduced by this high sensitivity to spurious laser beam phase changes will be described in the first part of this paper. Then other limitations on the performance and on the suggested types of sources that could be observed will be discussed.     

空间太阳望远镜星载图像压缩系统的研究

受存储容量和对地传输能力的限制,空间太阳望远镜(Space Solar Telescope,SST)15个CCD采集的科学数据必须在轨进行5倍的压缩。在分析了SST对图像处理的需求基础上;综合中德合作的离线压缩方案,以及国内的设计能力,提出实时在线压缩的方案;采用基于小波变换的压缩算法,DSP和FPGA器件,设计了星载压缩系统(Onboard DataCompression Unit,DCU)。仿真实验表明上述方法满足SST系统需求。     

Liquid crystal cell for space-borne laser rangefinder to space mission applications

Liquid crystal cell (LCC) for space-borne laser rangefinder to space mission applications was developed, manufactured and tested under cooperation between Military University of Technology (MUT) in Poland and Vavilov State Optical Institute (Vavilov SOI) in Russia. LCC operates in twisted nematic mode, commutating the polarization plane of a laser beam working at 1.064 ??m and the energy density not smaller than 0,15 J/cm² at the pulse duration about 8 ns. The transmission of LCC is not smaller than 95% at the aperture diameter not less than 15 mm. Switching on and switching off times in a 2.5-??m thick LCC driven by voltage of 10 V are not larger than 0.7 ms and 7 ms, respectively, in the operating temperature range from 20°C to 40°C. The LCCs developed in MUT were positively tested under space requirements in Vavilov SOI.     

A state space approach in phase shifting interferometry

The paper proposes a state space approach for the determination of phase distribution in an interferogram in the presence of a non-sinusoidal waveform, random noise, and the miscalibration of the piezoelectric device. In this approach we first estimate the phase step imparted to the piezoelectric transducer (PZT) before determining the phase distribution. A denoising procedure is applied with the knowledge of the state-feedback matrix prior to the extraction of the phase step. This step ensures a good estimation of the phase distribution even at low signal-to-noise ratios. The other salient features of the proposed concept lie in its ability to compensate the detector non-linearity and in the use of non-collimated beams. The comparison of the proposed method with other bench-marking algorithms shows that our approach is efficient and robust. The experimental results show the feasibility of the proposed approach.     

各向异性表面的椭偏测量的消光过程

本文描述了在正向入射条件下,当待测的各向异性反射面(如全息光栅)的两个笛卡儿本征矢方向与系统的指向有微小偏离时,椭偏测量的消光过程由理想的两步过程转变成多步过程。文中同时定量指出该偏离所造成的影响及应用。     

Exo-planet detection with the COROT space mission. I. A multi-transit detection criterion

In this Note, we present a detection criterion for exo-planets to be used with the space mission COROT. This criterion is based on the transit method, which suggests the observation of star dimming caused by partial occultations by planetary companions. When at least three transits are observed, we show that a cross-correlation technique can yield a detection threshold, thus enabling the evaluation of the number of possible detections assuming a model for the stellar population in the Galaxy.     

Prospects for atom interferometry

Atom interferometers were first realized ten years ago, and since then have evolved from beautiful demonstrations of quantum physics into instruments at the leading edge of precision measurement. In this article we trace the development of atom interferometry, looking at how the physical principles have been put into practice to achieve ground-breaking experiments. We also discuss new atom optical techniques that are becoming available and anticipate the ways in which the consequent improvements will provide new opportunities in metrology and the study of fundamental physics.     

Landau-Zener interferometry for qubits

One may probe coherence of a qubit by periodically sweeping its control parameter. The qubit is then excited by the Landau-Zener (LZ) mechanism. The interference between multiple LZ transitions leads to an oscillatory dependence of the energy absorption rate on the sweeping amplitude and on the period. This interference pattern allows to determine the decoherence time of the qubit. We introduce a simple phenomenological model describing this interferometer, and find the form of the interference pattern.Received: 21 October 2003, Published online: 8 December 2003PACS: 03.67.-a Quantum information - 85.25.Dq Superconducting quantum interference devicesD.A. Ivanov: Present address: Paul Scherrer Institute, 5232 Villigen PSI, Switzerland     

Two-pion interferometry for granular sources

A review on the two-pion Hanbury-Brown—Twiss (HBT) interferometry in the granular source model of quark-gluon plasma droplets is presented. The characteristic quantities of the granular source extracted by imaging analysis are presented and compared with the HBT radii obtained by the usual Gaussian formula fit. The signals of granular sources are presented.     

利用非线性Sagnac干涉法提高短脉冲信噪比

理论研究了影响Sagnac干涉法信噪比提升能力和效率的各项因素。通过控制脉冲的空间分布和衰减片透过率,能够有效提高Sagnac干涉法的效率。Sagnac干涉法提升信噪比的能力与入射脉冲的信噪比有关:入射脉冲信噪比越高,信噪比提升的量级就越大。在SILEX-Ⅰ超短超强脉冲激光装置上建立了实验平台。3 TW压缩器输出的超短超强脉冲光经衰减片进入Sagnac干涉仪,非线性介质为5 cm长的熔石英材料,衰减片透过率为55%。当入射脉冲能量为6.6 mJ时,利用三阶自相关仪测量得到脉冲的信噪比从使用Sagna干涉仪前的10-6提高到了10-7,此时出射脉冲的能量为1.6 mJ,效率为24%。该方法对光束口径没有限制,能够用于大能量条件下短脉冲信噪比的提升。     

Tunable-optical-filter-based white-light interferometry for sensing

We describe tunable-optical-filter-based white-light interferometry for sensor interrogation. By introducing a tunable optical filter into a white-light interferometry system, one can interrogate an interferometer with either quadrature demodulation or spectral-domain detection at low cost. To demonstrate the feasibility of effectively demodulating various types of interferometric sensor, experiments have been performed using an extrinsic Fabry-Perot tunable filter to interrogate two extrinsic Fabry-Perot interferometric temperature sensors and a diaphragm-based pressure sensor.     

Dispersion compensation for atom interferometry

A new technique for maintaining high contrast in an atom interferometer is used to measure large de Broglie wave phase shifts. Dependence of an interaction induced phase on the atoms' velocity is compensated by applying an engineered counterphase. The counterphase is equivalent to a rotation, is precisely determined by a frequency, and can be used to measure phase shifts due to interactions of unknown strength. Phase shifts of 150 rad (5 times larger than previously possible) have now been measured in an atom beam interferometer, and we suggest that this technique can enable comparisons of atomic polarizability with precision of one part in 10,000.     

The RETE experiment for the TSS-1 mission

Summary This paper describes the RETE (Research on Electrodynamic Tether Effects) experiment mounted on board the TSS (Tethered-Satellite System) satellite which was deployed on a cable from the space Shuttle Atlantis during the TSS mission flown in August 1992. The experiment layout and its modes of operation are described in detail. To give an idea of RETE capabilities and actual performance during the mission, samples of measurements are also presented.