Effect of four-wave mixing interference on spectrally separated channels in passive optical networks

The phenomenon of four-wave mixing in passive optical networks with wavelength-division multiplexing of channels has been studied. This paper presents the results of modeling the distribution of combination frequencies over the spectrum as a function of the number of channels and the channel frequency spacing. To suppress crosstalk between the channels at combination frequencies, it is proposed to divide the spectrum into two parts and select a guard band between them. The effect of combination frequencies on the signal transmission quality is considered as a function of the channel power, channel frequency spacing, and transmission length.     

A versatile cantilever beam magnetometer for ex situ characterization of magnetic materials

We have designed, fabricated, and made operational an ex situ cantilever beam magnetometer (CBM), which is versatile in the sense that it can measure most of the magnetic properties of a material in all probable shapes. The working principle of a CBM is discussed considering the magnetic torque into the beam theory. The individual components of the instrument are described in details and experiments were performed on the bulk materials, pellets of nanoparticles, ribbon samples, and thin films, and the magnetization, magnetostriction, and magnetocrystalline anisotropy were studied. This magnetometer is inexpensive, but versatile and would be suitable for the research as well as teaching laboratories.     

投影光刻离轴照明用衍射光学元件设计

离轴照明（OAI：Off-axis Illumination）作为一种重要的分辨率增强技术（RET：Resolution Enhancement Technology）被广泛的应用于投影光刻系统。使用衍射光学元件（DOE：Diffractive Optical Element）作为光刻照明系统的光束整形器件,能够在保持较高照明效率的基础上精确控制离轴照明光束的形状及光强分布。本文利用基于傅立叶变换的分步迭代方法进行了该类DOE的优化设计。DOE采用了多台阶位相结构,设计所得8台阶DOE设计结果分别实现了偶极、四极、环形及Bulls-Eye等照明方式,其照明效率都达到了80%以上,与目标光强分布的均方根偏差均小于7％。     

Magnetic microrheometer for in situ characterization of coating viscosity

A magnetic microrheometer has been designed to characterize the local viscosity of liquid-applied coatings in situ during solidification. The apparatus includes NdFeB magnets mounted on computer-controlled micropositioners for the manipulation of ～1?μm diameter superparamagnetic particles in the coating. Magnetic field gradients at 20-70 T/m are generated by changing magnet size and the gap distance between the magnets. A specimen stage located between two magnets is outfitted with a heater and channels to control process conditions (temperature and air flow), and a digital optical microscope lens above the stage is used to monitor the probe particle position. Validation studies with glycerol and polyimide precursor solution showed that microrheometry results match traditional bulk rheometry within an error of 5%. The viscosities of polyvinyl alcohol (PVA) solution and polyimide precursor solution coatings were measured at different shear rates (0.01-5?s(-1)) by adjusting the magnetic field gradient. The effect of proximity to the substrate on the particle motion was characterized and compared with theoretical predictions. The magnetic microrheometer was used to characterize the time-viscosity profile of PVA coatings during drying at several temperatures. The viscosity range measured by the apparatus was 0.1-20?Pa?s during drying of coatings at temperatures between room temperature and 80?°C.     

Thermal sensor for in situ flying height measurements of optical flying heads

The application of flying head technology in optical recording promises a considerable increase in recording density. It may be used for both far field and near field recording. For dynamic in situ flying height and flight attitude measurements, a prototype of a thermal test head has been developed. It takes advantage of the heat transfer in sub-micrometer air bearings as well as its dependence from the air gap width. Such a test head has a slider with a similar air bearing surface as the recording head, but with thermo-resistive sensors that are energized by Joule's heat and embedded at each of the four corners. The paper describes the head design and the fabrication technology and provides first experimental test results as well.     

Newly developed standard conductance element for in situ calibration of high vacuum gauges

A new leak element, which is named as “standard conductance element (SCE)”, has been developed for in situ calibration of ionization gauges (IGs) and quadrupole mass spectrometers (QMSs). The SCE is made of a stainless-steel sintered filter with the pore size of less than 1 μm. Since the gas flow through the SCE satisfies the molecular flow condition even at the pressure up to 10⁴ Pa, some useful characteristics of molecular flow are available. The SCE is supplied to users with a calibration certificate described its molecular conductance. Users can introduce optional test gases with the known flow rate to their vacuum chamber through the SCE in their laboratories. The overview of the SCE, the calibration method and recommended practices are introduced.     

High pressure rheometer for in situ formation and characterization of methane hydrates

We present a novel setup for a high pressure rheometer operating with concentric cylinders geometry for in situ studies of hydrate formation and rheological characterization. The apparatus uses an external high pressure mixing cell to saturate water-in-oil emulsions with methane gas. The capability of mixing combined with a true rheometer design make this apparatus unique in terms of setup and sample formation. We have used the apparatus to form gas hydrates in situ from water-in-oil emulsions and characterize suspension rheological properties such as yield stress and shear-thinning behavior.     

Discrete element method for the characterization of soil properties in Plate-Sinkage tests

The Discrete element method (DEM) is used for solving microscopic mechanical behaviors of granular materials and has the advantage of being able to analyze the wheel-soil interactions on the off-road ground because soil deformation under a moving wheel is a discontinuous, non-uniform and nonlinear phenomenon. However, a challenge for applying DEM to the soil analysis is that determination of DEM parameters is not rooted in a clear understanding of relationships between the DEM parameters and soil conditions. This study modeled the plate-sinkage test based on DEM and produced the soil characteristic properties of the virtual soils to reveal effects of the DEM parameters on the vertical bearing capacity of the soil. A nominal model of the plate-sinkage test was developed with a chosen set of the DEM parameters, and its model results were compared with experimental data of actual Jumunjin sand. Also, parametric studies were conducted on particle density, Young’s modulus, friction coefficient and rolling friction coefficient.

     

Invited review article: Photopyroelectric calorimeter for the simultaneous thermal, optical, and structural characterization of samples over phase transitions

The study of thermophysical properties is of great importance in several scientific fields. Among them, the heat capacity, for example, is related to the microscopic structure of condensed matter and plays an important role in monitoring the changes in the energy content of a system. Calorimetric techniques are thus of fundamental importance for characterizing physical systems, particularly in the vicinity of phase transitions where energy fluctuations can play an important role. In this work, the ability of the Photopyroelctric calorimetry to study the versus temperature behaviour of the specific heat and of the other thermal parameters in the vicinity of phase transitions is outlined. The working principle, the theoretical basis, the experimental configurations, and the advantages of this technique, with respect to the more conventional ones, have been described and discussed in detail. The integrations in the calorimetric setup giving the possibility to perform, simultaneously with the calorimetric studies, complementary kind of characterizations of optical, structural, and electrical properties are also described. A review of the results obtained with this technique, in all its possible configurations, for the high temperature resolution studies of the thermal parameters over several kinds of phase transitions occurring in different systems is presented and discussed.     

在多相流变介质参数测量中数据交换的实现方法

本文主要介绍在间接式多相流变介质参数测量中，８０９８多机系统串行通讯的实现方法。在讨论系统结构的基础上，着重说明实现实时数据交换的接口和软件设计的特点。     

A high-vacuum deposition system for in situ and real-time electrical characterization of organic thin-film transistors

We present a home-built high-vacuum system for performing organic semiconductor thin-film growth and its electrical characterization during deposition (real-time) or after deposition (in situ). Since the environment conditions remain unchanged during the deposition and electrical characterization process, a direct correlation between growth mode and electrical properties of thin film can be obtained. Deposition rate and substrate temperature can be systematically set in the range 0.1-10 ML∕min and RT-150 °C, respectively. The sample-holder configuration allows the simultaneous electrical monitoring of up to five organic thin-film transistors (OTFTs). The OTFTs parameters such as charge carrier mobility μ, threshold voltage V(TH), and the on-off ratio I(on)∕I(off) are studied as a function of the semiconductor thickness, with a submonolayer accuracy. Design, operation, and performance of the setup are detailed. As an example, the in situ and real-time electrical characterization of pentacene TFTs is reported.     

Performances of interferometric optical transmission diagnostic for in situ and real-time control of magnetron sputtering deposition process

A convenient and simple in situ and real-time method to control PVD processes for transparent thin films deposition on transparent substrate is described in this paper. This method designed for the glass industry and tested today in on-line monitoring, allows to control the thickness and complex indices and then the good running of the treatment. This method consists of a simple measurement of the interferential transmission through the substrate and the deposit. After recalling the principles of this classical method, the optical sensitivity parameters linked with the use of an inverse calculation method are evaluated and commented on. It is shown that, as expected when the refraction index values of the deposited material are close to those of the substrate, the sensitivity of the process control is low. It is often the case for the deposits used in the glass industry. Nevertheless to exploit this very useful method of process control, a solution currently tested on production lines is described here. To boost the sensitivity of the interferential transmission diagnostic it is shown that the measurements can be made through a high refractive index thin film layer, pre-deposited on the substrate with an adequate thickness.     

管状电热膜元件工业化热喷镀过程中传输方案的反求工程设计

本文应用功能反求分析原理对管状电热膜元件在工业化热喷镀过程中的传输方式进行了反求工程设计。     

Development of a synchrotron biaxial tensile device for in situ characterization of thin films mechanical response

We have developed on the DIFFABS-SOLEIL beamline a biaxial tensile machine working in the synchrotron environment for in situ diffraction characterization of thin polycrystalline films mechanical response. The machine has been designed to test compliant substrates coated by the studied films under controlled, applied strain field. Technological challenges comprise the sample design including fixation of the substrate ends, the related generation of a uniform strain field in the studied (central) volume, and the operations from the beamline pilot. Preliminary tests on 150 nm thick W films deposited onto polyimide cruciform substrates are presented. The obtained results for applied strains using x-ray diffraction and digital image correlation methods clearly show the full potentialities of this new setup.     

Micro optical power meter for direct in situ measurement of light transmitted from microscopic systems and focused on micro-samples

This paper reports a micro optical power meter which is able to perform effective and precise measurement on the optical power at the focus of different microscopic systems. The power meter can be easily placed on the stages of different microscopes and even partly immersed into solution to directly measure the optical power transmitted from the microscope objective and focused on the sample suspended in solution. The testing experiments demonstrated that the power meter has the characteristics of high precision, excellent linearity, high sensitivity, good stability, and high responding speed. It can accurately measure power levels from 0.1 to 50 mW in visible wavelength in various conditions and environments, which may encounter in practical applications. The optical power measurements using the power meter performed in some biological cell culturing solutions and in air for the same laser light reveal the first time that the powers measured in solutions were about 5%-8% greater than that measured in air at the same position. This not only suggests the necessity of performing direct measurement in situ in solution to obtain the real optical power projected on the suspended samples, but also indicates that such a micro optical power meter can meet almost all the requirements of optical power measurement in different fields from biomedicine to material sciences.     

Designing a miniaturised heated stage for in situ optical measurements of solid oxide fuel cell electrode surfaces, and probing the oxidation of solid oxide fuel cell anodes using in situ Raman spectroscopy

A novel miniaturised heated stage for in operando optical measurements on solid oxide fuel cell electrode surfaces is described. The design combines the advantages of previously reported designs, namely, (i) fully controllable dual atmosphere operation enabling fuel cell pellets to be tested in operando with either electrode in any atmosphere being the focus of study, and (ii) combined electrochemical measurements with optical spectroscopy measurements with the potential for highly detailed study of electrochemical processes; with the following advances, (iii) integrated fitting for mounting on a mapping stage enabling 2-D spatial characterisation of the surface, (iv) a compact profile that is externally cooled, enabling operation on an existing microscope without the need for specialized lenses, (v) the ability to cool very rapidly, from 600 °C to 300 °C in less than 5 min without damaging the experimental apparatus, and (vi) the ability to accommodate a range of pellet sizes and thicknesses.     

A novel test rig for in situ and real time optical measurement of the contact area evolution during pre-sliding of a spherical contact

An experimental test rig was developed in order to investigate elastic–plastic single micro-spherical contact under combined normal and tangential loading. This novel apparatus allows in situ and real time direct optical measurement of the real contact area (RCA) evolution in pre-sliding. It also allows relative displacement measurements under very low rates of tangential loading (down to 0.01 N/s) to capture accurately the fine details at sliding inception. This is achieved by piezoelectric actuation in closed loop feedback control in addition to synchronization with data and image acquisition to obtain real time measurement. The RCA measurement is realized by direct optical observation technique, whereas two different image processing algorithms were implemented for the elastic and the elastic–plastic contact regimes. The various features and capabilities of the test rig are presented along with some preliminary experimental results of RCA and friction behavior to assess its performance.     

Frequency discriminators for the characterization of narrow-spectrum heterodyne beat signals: application to the measurement of a sub-hertz carrier-envelope-offset beat in an optical frequency comb

We describe a radio-frequency (RF) discriminator, or frequency-to-voltage converter, based on a voltage-controlled oscillator phase-locked to the signal under test, which has been developed to analyze the frequency noise properties of an RF signal, e.g., a heterodyne optical beat signal between two lasers or between a laser and an optical frequency comb. We present a detailed characterization of the properties of this discriminator and we compare it to three other commercially available discriminators. Owing to its large linear frequency range of 7 MHz, its bandwidth of 200 kHz and its noise floor below 0.01 Hz(2)/Hz in a significant part of the spectrum, our frequency discriminator is able to fully characterize the frequency noise of a beat signal with a linewidth ranging from a couple of megahertz down to a few hertz. As an example of application, we present measurements of the frequency noise of the carrier envelope offset beat in a low-noise optical frequency comb.