Simple, stable, and compact multiple-reflection optical cell for very long optical paths

A new type of multiple-reflection optical cell is presented. One of the main advantages of this type of cell is that it can be made of standard mirrors without particular tolerance while allowing a great number of reflections and thus a large optical path, only limited by the reflection coefficient of the mirrors. The configuration is simple, compact, stable, and cheap. This cell consists of three mirrors as in a White cell but its principle is different. It behaves as a multiplier of a Herriott cell from which it inherits the opto-mechanical stability qualities. The Herriott cell and the White cell are two particular cases of this type of cell. As examples, a demonstrator and an absorption cell contained in a volume of 5 l are presented. The first device is usable with a laser in visible light. The second device is usable with an infrared laser diode for the detection of atmospheric trace species.     

Laser-to-fiber optical coupling scheme with a long working distance by use of thermally overexpanded fiber

A laser-diode-optical-fiber coupling scheme that uses aspherically ended thermally overexpanded fiber is proposed. The scheme is verified by both an analytical formalism and a wide-angle beam-propagation method analysis in cylindrical coordinates.     

采用长工作距离物镜的低噪声相移数字全息显微研究

在数字全息显微技术中,为了提高测量精度,提出了一种利用长工作距离物镜的相移数字全息显微的测量装置和方法。该装置采用LED作为照明光源,可以有效地抑制相位噪声,提高了重建精度。通过在长工作距离物镜和样品之间加入分光棱镜的方法,构建了一种准物参共路的迈克尔逊干涉仪。该装置结构简单,调整方便,在部分相干光照明时,容易实现干涉。重建时,采用盲相移干涉技术,结合两步盲相移算法,重建出物体的表面相位分布。实验中,分别采用LED照明和He-Ne激光照明,测量了一个反射式USAF1951分辨率板的高度分布。结果表明,两者的测量结果相互吻合,但是LED照明时的噪声与激光照明时相比降低了70%。此外,为了进一步验证装置的有效性,使用该装置对刻于硅基底的微纳矩形台阶进行测量,测量结果与标称值具有良好的一致性,表明该装置在微结构的形貌测量方面有广阔的应用前景。     

High-accuracy measurement of 240-m distance in an optical tunnel by use of a compact femtosecond laser

A high-accuracy optical distance meter with a mode-locked femtosecond laser is proposed for distance measurements in a 310-m-long optical tunnel. We measured the phase shift of the optical beat component between longitudinal modes of a mode-locked laser. A high resolution of 50 mum at 240-m distance was obtained without cyclic error correction. The group refractive index of air is automatically extracted to an accuracy of 6 parts per million (ppm) by two-color measurement with the pulses of fundamental and second-harmonic wavelengths. Finally, an absolute mechanical distance of 240 m was obtained to within 8-ppm accuracy by use of a series of beat frequencies with the advantage of a wide range of intermode frequency, together with the results of the two-color measurement.     

A compact planar positron imaging system

A planar imaging system for positron-emitting radiotracers was developed and its physical performance was evaluated. The new device consists of two opposing planar detectors, each having 4 (columns) $\text{×}\text{6}$ (rows) detector units, and each unit composed of 10×10 arrays of $\text{2×2×20}\text{mm}{}^3$ pillars of Bi₄Ge₃O₁₂ (BGO) scintillators and a metal-packaged position-sensitive photomultiplier tube. The system is very compact and has a simple structure that allows versatile positioning of detectors in the horizontal or vertical mode. Focal plane images are constructed from coincidence data collected by opposing planar detectors. The system provides good quality images even in a short period of time or with low tracer activity. Spatial resolutions of 1.6–$\text{2.1}\text{mm}$ FWHM were achieved for the entire field of view. The sensitivity was $\text{107}\text{cps}\text{/}\text{kBq}\text{/}\text{ml}$ measured in a uniform flat phantom. In this study, the capability of the new system was demonstrated by the imaging of radiotracer distribution in rats and plants.     

Designing an optimal turnover-based storage rack for a 3D compact automated storage and retrieval system

Compact, multi-deep (3D) automated storage and retrieval systems (AS/RS) are becoming increasingly popular for storing products. We study such a system where a storage and retrieval (S/R) machine takes care of movements in the horizontal and vertical directions of the rack, and an orthogonal conveying mechanism takes care of the depth movement. An important question is how to layout such systems under different storage policies to minimize the expected cycle time. We derive the expected single-command cycle time under the full-turnover-based storage policy and propose a model to determine the optimal rack dimensions by minimizing this cycle time. We simplify the model, and analytically determine optimal rack dimensions for any given rack capacity and ABC curve skewness. A significant cycle time reduction can be obtained compared with the random storage policy. We illustrate the findings of the study by applying them in a practical example.     

Compact interferometric optical tweezer for patterned trapping and manipulation of polystyrene spheres and SWCNTs

We demonstrate a simple and compact optical interferometric unit combined with a conventional optical tweezer system for simultaneous multiple trapping and micromanipulation of mono-dispersed polystyrene spheres and aggregation of small-floating clusters of single-walled carbon nanotubes (SWCNTs). The interferometric unit was made compact by means of coating a thin layer of aluminum oxide on one side of the cubic beam splitter (CBS) which works as a static reference mirror and an adjustable mirror was mounted on a XYZ translational stage facing the other adjacent side of the CBS. Thus, the developed interferometric unit is quite analogous to a Michelson interferometer but is compact. Sinusoidal interference fringes with variable carrier frequency and orientations were generated. The interference fringes were then used for multiple trapping of polystyrene spheres along bright fringes resulting in pattern formation and also the aggregation of tiny floating clusters of SWCNTs. The proposed system is compact and easy to align because of its common-path geometry.     

Cantor network, control algorithm, two-dimensional compact structure and its optical implementation

A compact integrating module technique for packaging a optical multistage Cantor network with a polarization multiplex technique is suggested. The modules have a unique configuration, which is the solid-state combination of a polarization rotator, double birefringent slabs, and a 2 × 2 switch array. The design and the fabrication of an eight-channel optical nonblocking Cantor network are demonstrated, and a fast-setup control algorithm is developed. The network systems are easy to assemble and insensitive to environment disturbance.     

Confocal microscope with large field and working distance

A confocal microscope that uses separate, noncollinear objective lenses for illumination and collection makes it possible to work 20 mm from a sample with a field of view of 2.25 mm across and still achieve lateral and axial resolutions below 5 mum. The design is expected to have application to in vivo confocal microscopy, allowing a field of view and section thickness similar to those used by pathologists in examining excised tissue.     

A compact optical wavelength splitter in one-dimensional photonic crystal waveguides

A fundamental T-branch in one-dimensional photonic crystal waveguides based on the omnidirectional reflection is constructed. Numerical simulations of this T-branch indicate that without any structural optimization, four high reflectance peaks and three high transmittance peaks appear alternately within a wide enough frequency band. The T-branch with the unique transmission characteristics can be used as a wavelength splitter. Combining the fundamental T-branch with flexible bends of one-dimensional photonic crystal waveguides, we construct simple and compact wavelength splitters with arbitrary branching angles. Those wavelength splitters are expected to be applied to high density photonic integrated circuits.     

远程分布式光纤温度传感系统的设计和制造

为了测量长距离大范围空间分布温度场,设计制造出30km远程光纤温度传感器。基于光纤放大的反斯托克斯背向拉曼自发散射测温原理,对系统进行了优化设计。用1550nm掺铒光纤激光器作为抽运源,采用高速瞬态波形采样技术,累加平均等信号处理技术,解决了远处背向反斯托克斯弱信号的检测问题。采用了智能化恒温技术,使主要元器件在恒温条件下工作,解决了工程应用中环境的适应性。远程分布光纤拉曼温度传感器系统已达到的主要技术指标如下:光纤长度31km,测温范围0-100℃(可扩展),温度测量不确定度为±2℃,温度分辨力为0.1℃,测量时间为432s,空间分辨力为4m。     

A compact system for timing and energy pulse generation

This paper describes a new kind of pulse generator, able to provide not only two pairs of coincident pulses, with continuously variable amplitude (0–5 V) for each pulse and delay (40–150 μs) between the two pairs — energy simulation — but also the corresponding timing signals — time of flight simulation — with different intrinsic variable delays ranging from 50 ps up to 128 ns, in steps of 50 ps, with a proper time resolution better than 15 ps. Some experimental results, obtained using the present device, are also reported.     

A compact microcomputer-based deep level transient spectroscopymeasurement system

A specifically designed system for deep-level transient spectroscopy (DLTS) measurement is described. It is compact and fully automated, can measure all the spectra in just one temperature scan, and permits simultaneous analysis of two devices. The user sets up the measurement conditions with a reduced number of commands. This makes the system very flexible and versatile. A self-scaled gain output amplifier has been incorporated to provide the maximum DLTS signal amplitude compatible with the input range of the analog-to-digital (A/D) converter. This self-scaling allows the detection of traps with a large amplitude range. Up to 90 sampling times can be selected for each transient. To improve the signal-to-noise ratio (SNR), as many as 32768 scans may be accumulated for averaging. Improvements as high as 45 dB have been used to characterize deep centers in AlGaAs/GaAs devices grown by liquid-phase and molecular-beam epitaxies     

A muprobe system with a compact electrostatic lens

A muprobe system has been constructed for a 4.75 MV Van de Graaff using a compact electrostatic quadrupole triplet lens. The beam-energy homogenizer is used to improve the beam transmission through slits. The beam intensity profile is measured by scanning the beam on a copper grid. The minimum beam-spot size obtained is (4.5 ± 1.6) μm × (12.2 ± 2.1) μm for 3 MeV protons with a beam current of 1.5 nA.     

高纯致密的长余辉块体材料的制备方法的研究

在高温固相法的基础上,通过在900℃对原料进行预处理,成功制备出一种高纯、致密的长余辉块体材料。通过扫描电镜对其表面形态进行表征,结果表明该块体材料致密、均匀、无裂纹;并通过XRD 测试分析发现预处理后SrAl2O4 相已基本形成。     

Instruments and artisanal practices in long distance oceanic voyages

Scientific instruments are not neutral artefacts; the perception of their value is greatly determined not only by the objects themselves and the function they perform, but also by the context of their use. In the 16th and 17th centuries, scientific instruments – not only nautical ones – acquired a prominent place in European societies that greatly transcended the specific narrow professional circles that used them. This has already been noted as being an important feature in the development of science in early modern Europe. But exactly how did this happen? Following other recent studies, I argue in this paper that in order to understand this phenomenon one has to look carefully at artisanal practices of the period.     

Versatile, fully automated, microfluidic cell culture system

There is increasing demand for automated and quantitative cell culture technology, driven both by the intense activity in stem cell biology and by the emergence of systems biology. We built a fully automated cell culture screening system based on a microfluidic chip that creates arbitrary culture media formulations in 96 independent culture chambers and maintains cell viability for weeks. Individual culture conditions are customized in terms of cell seeding density, composition of culture medium, and feeding schedule, and each chamber is imaged with time-lapse microscopy. Using this device, we perform the first quantitative measurements of the influence of transient stimulation schedules on the proliferation, osteogenic differentiation, and motility of human primary mesenchymal stem cells.     

Implementation of a compact, four-stage, scalable optical interconnect for photonic backplane applications

We report on the implementation of a dense 512-beam free-space optical interconnect linking four optoelectronic VLSI chips at the backplane level. The system presented maximizes the positioning tolerances of the components by use of slow f-number (f/16) Gaussian beams and oversized apertures. A beam-clustering scheme whereby a 4 x 4 array of beams is transmitted by each minilens is used to provide a high channel density. A modular approach is used to decrease the number of degrees of freedom in the system and achieve passive alignment of the modules in the final integration phase. A design overview as well as assembly and experimental results are presented.     

Performance of a compact, hybrid optical evanescent-wave sensor for chemical and biological applications

We describe a hybrid evanescent-wave sensor component that we fabricated by using an integrated optical interferometer with a specially adapted photodetector array. The design of the interferometer is based on the use of tapered waveguides to obtain two intersecting collimated beams. Phase shifts can be measured with an angular precision of better than 10(-3) rad, which corresponds to a superstrate index change inferior of 10(-6) with our structure. The interest in the device as a chemical sensor is experimentally demonstrated. The same optical component could be used in a variety of other sensor applications, e.g., biological and immunological sensors.