Evaluation of a femtosecond fiber laser for two-photon fluorescence correlation spectroscopy

This work evaluates a femtosecond fiber laser for use in two-photon fluorescence fluctuation spectroscopy. Fiber lasers present an attractive alternative to Ti:Sapphire systems because of their compact size and portability. Autocorrelation of the second harmonic generation signal from the laser demonstrates that its stability is sufficient for two-photon fluorescence correlation spectroscopy. Fluorescence correlation spectroscopy autocorrelation traces were well fit by a Gaussian-Lorentzian squared model with a beam waist near the diffraction limit for the 810 nm wavelength. A photon counting histogram collected with this system also fit nicely to a single-species model, further demonstrating the quality of the focal shape. The authors conclude that the output from the femtosecond fiber laser is sufficiently stable and has a high enough quality beam shape for fluctuation fluorescence methods, and thus represents an effective, compact, readily portable two-photon excitation source.     

Laser ion source with a double pulse laser system

To extend an ion beam pulse of a laser ion source, multiple laser shots could be used. To check the feasibility of this idea, we tested double laser irradiations on an iron target. When the interval of the two laser shots is longer than 10 μs, the obtained ion current profile was expressed as a sum of two individual expanded laser plasmas. However, if the interval is too close, a current reduction was observed. This technique can be effectively applied to low charge state ion production.     

Picosecond-resolution fluorescence lifetime measuring system with a cw laser and a radio

A procedure for measurement of fluorescence lifetimes with picosecond time resolution is described. A cw laser beam is modulated with a standing-wave acousto-optic modulator. The modulated beam is split; one part serves as a reference beam, the other part excites the fluorescent sample. The sample flourescence and the reference beam, attenuated and delayed optically to be equal in amplitude and opposite in phase to the fluorescence, are incident onto a single photomultiplier tube. The thus achieved photodetector ac null is monitored either by an AM radio, whose intermediate-frequency signal is displayed on an oscilloscope, or by a spectrum analyzer. With 30-MHz light modulation and the radio, lifetimes could be determined with resolution better than 15 ps. With the spectrum anlyzer and 170-MHz light modulation frequency we have achieved 4-ps lifetime resolution. Correction for photomultiplier transit time versus incident wavelength is made.     

Description and characteristics of a wide-band linear circuit for pulse amplification

A wide-band, linear, pulse amplifier stage was designed and tested. The closed-loop gain is approximately 10, the gain-bandwidth product is 350 MHz, and the integral nonlinearity is <0.05%.     

A compact high-voltage pulse generator with opening insulated-gate bipolar transistor switch and a high pulse repetition rate

A small-size high-voltage (～20 kV) microsecond pulse generator, which is based on a pulse transformer and loaded into a reactor with a pulse corona discharge, is described. Insulated-gate bipolar transistors (IGBTs) that form the switch are used in the low-voltage circuit of the generator. When the switch is open, voltage pulses with an amplitude of up to 1000 V are created across it and, hence, across the primary winding of the transformer. The pulse repetition rate of the generator is ～20000 pulses/s.     

A laser system for the parametric amplification of electromagnetic fields in a microwave cavity

We describe recent improvements in the development of the high power laser system used in the motion induced radiation (MIR) experiment to amplify electromagnetic fields inside a microwave cavity. The improvements made on the oscillator stabilization, the pulse train shaping device, and the spatial beam uniformity are reported.     

Study on the light receiving characteristics of a compact solar power generation system with a plant shoot shape

The distribution of solar cell modules is planned by referring to a plant shoot configuration. The object of this planning is to develop a solar power generation system with low directivity and a low installation space. In this study, the amount of insolation which reaches a plant shoot within an arbitrary period was investigated using the LAPS. The LAPS algorithm consists of the Genetic Algorithm and Monte-Carlo Method. In this analysis method, the optimal configuration of the shoot at the time of maximizing the amount of light received was clarified. The position of the light source in the representation day of mid-term to summertime has a wide movable range of the plant shoot configuration. Since the amount of light received of “the leaves arranged to the level surface” and “the plant shoot configuration optimized every month” is measured, light receiving characteristics of the Kenaf shoot model and coptophyllus shoot models were investigated. This paper was presented at the 7th JSME-KSME Thermal and Fluids Engineering Conference, Sapporo, Japan, October 2008. Shin’ya Obara received his B.S. and M.S. degree in Mechanical Engineering from Nagaoka University of Technology, Japan, in 1987. He then received his Ph.D. degrees from Hokkaido University in 2000. Dr. Obara is currently a Professor at the Department of Electrical and Electronic Engineering at Kitami Institute of Technology in Hokkaido, Japan. Dr. Obara’s research interests include fuel cell, renewable energy, power system and micro-grid. His major academic field is thermal engineering, power system and environmental engineering.     

Time correlation method for measuring fluorescence decays with a cw laser

A simple experimental approach to measuring fluorescence decay by time correlation signal analysis is described. The approach allows the use of continuous wave excitation and inexpensive detection-signal processing apparatus. The technique is demonstrated using a cw He-Cd laser. The transient response of the instrument is 0.88 ns, limited by the photomultipliers. The fluorescence lifetime of rose bengal in ethanol is determined, in absence of reorientation relaxation, to be 0.66+/-0.04 ns.     

A high-speed system for strain and temperature measurements based on fiber Bragg sensors

This work is devoted to issues related to development of measuring equipment for investigation of thermal and deformation processes with the help of sensors based on fiber Bragg gratings. A high-speed device for processing signals from Bragg sensors, developed by the Institute for Physical High Technology, Jena, with the participation of the Institute of Radio Engineering and Electronics, Russian Academy of Sciences (Ul’yanovsk Branch), is described. It can serve as a basis for development of fiber-optic measuring systems for strain and temperature monitoring. The device uses a broadband optical radiator and a miniature polychromator for a wavelength of ～800 nm as well as a digital signal-processing module based on an ADSP21062 processor. The measuring system allows simultaneous processing of signals from 19 fiber Bragg sensors, scanned with a period of <1 ms.     

Real-time displacement measurements with a Fabry-Perot cavity and a diode laser

We present the basic operating principles of a traceable measurement system suitable for use with atomic force microscopes (AFMs) and nanometer-resolution displacement sensors. Our method is based upon a tunable external-cavity diode laser system which is servo-locked via a phase-modulated heterodyne locking technique to a Fabry-Perot interferometer cavity. We discuss mechanical considerations for the use of this cavity as a displacement metrology system and we describe methods for making real-time (sub 10 ms sampling period) measurements of the optical heterodyne signals. Our interferometer system produces a root-mean-squared (RMS) displacement measurement resolution of 20 pm. Two applications of the system are described. First, the system was used to examine known optical mixing errors in a heterodyne Michelson interferometer. Second, the Fabry-Perot interferometer was integrated into the Z axis of a commercial AFM scanning stage and used to produce interferometer-based images of a 17 nm step height specimen. We also demonstrate atomic resolution interferometer-based images of a 0.3 nm silicon single atomic step-terrace specimen.     

Fabrication of microgrooves on a curved surface by the confocal measurement system using pulse laser and continuous laser

In order to fabricate microgrooves on a curved surface, the curved surface was measured with a confocal system and then it was used for laser microprocessing. This paper proposes a new method of using a pulse laser for the confocal system to measure the curved surface. It also compares the conventional way of using a continuous laser and a new way of using the pulse laser with the confocal system. Using the data measured with the pulse laser for fabrication, microgrooves were fabricated on a curved surface. The width of the fabricated microgroove was 10 μm and the depth was 27 μm. The microgroove fabricated on a curved surface as a part of this study can be used in injection molding to manufacture a micropatterned plastic surface at a low cost. This plastic surface can be applied for a superhydrophobic surface, a self-cleaning surface, or a biochip.     

A system and methodologies for absolute quantum efficiency measurements from the vacuum ultraviolet through the near infrared

In this paper we present our system design and methodology for making absolute quantum efficiency (QE) measurements through the vacuum ultraviolet (VUV) and verify the system with delta-doped silicon CCDs. Delta-doped detectors provide an excellent platform to validate measurements through the VUV due to their enhanced UV response. The requirements for measuring QE through the VUV are more strenuous than measurements in the near UV and necessitate, among other things, the use of a vacuum monochromator, good dewar chamber vacuum to prevent on-chip condensation, and more stringent handling requirements.     

Probing DNA structure and function with a multiwavelength fluorescence confocal laser microscope

Three levels of organization in DNA structure in the interphase cell nucleus are assessed by confocal laser scanning microscopy: (i) the conformational state of the double helix; (ii) the distribution of eu- and heterochromatin; and (iii) the localization of replication complexes throughout S phase. Multi-parameter measurements were carried out in each optical section using two laser sources and combined stereoscopic reconstructions were used to assess the co-localization of nuclear components. DNA is highly polymorphic and can adopt a variety of different helical conformations as well as unusual structures (curved, cruciform, multi-stranded). We have assessed by laser scanning microscopy the presence of left-handed Z-DNA in polytene chromosomes of Diptera as well as the spatio-temporal distribution of Z-DNA binding proteins in whole-mount Drosophila embryos and ovaries. We have determined the 3-D distribution of replication sites relative to heterochromatin regions, nucleoli and nuclear membrane by using short pulses of BrdU incorporation in synchronized mouse and human fibroblasts. Replication sites were visualized with a monoclonal anti-BrdU antibody combined with DNA fluorescent staining and antibody labelling of nuclear lamin. The implications of dynamic DNA movement and structural rearrangement to the organization of the nucleus in domains are discussed.     

脉冲编码器、测速发电机性能自动测试分析系统

脉冲编码器、测速发电机是传动系统中常用的速度传感器,其性能分坏直接影响控制系统的品质指标。本文设计实现了一种基于微机脉冲编码器,测速发电机性能自动测试系统,对该系统的硬件构成和软件分析功能进行了详细讨论。     

Optical and thermal processes involved in ultrafast laser pulse interaction with a field emitter

In the interaction between ultrafast laser pulses and a field emitter both optical and thermal processes are involved. In this paper, these physical process, and their timescales, are experimentally explored. Simple models are proposed to explain the observed experimental behaviour, and the influence of various parameters are investigated. In the case of optical processes, it is shown that the optical field is greatly enhanced at the tip apex, and that field evaporation could be induced by an optical non-linear effect called optical rectification. In the case of thermal processes, it is shown that the temperature rise because of light absorption can be determined and that the cooling process of the tip surface can be studied by pump probe measurements.     

Thermodynamic analysis of a novel compact power generation and waste heat operated absorption,ejector-jet pump refrigeration cycle

An R-152a ejector-jet pump refrigeration cycle and a LiBr-H₂O absorption refrigeration cycle have been integrated with a renewable energy power generator for making a proposed ‘novel compact cogeneration cycle’. The exergy analysis of this proposed cycle leads to a possible performance improvement. Nearly 71.12% of the input exergy is destructed due to irreversibilities in the different components. The useful exergy output is around 7.12%. The exhaust exergy lost to the environment is 21.76%, which is lower than the exhaust energy lost 37.6% of the input energy, while the useful energy output is approximately 19.3%. The refrigerants used and the exhaust gas emissions samples are found to be favourable for reducing the global environmental related problems. The results also show that the coupling of the entrainment ratios of the ejector and jet pump has great effect on the exergy and energy efficiency.     

激光诱导纳秒时间分辨荧光技术原位检测环境中多环芳烃的应用及展望

介绍激光诱导纳秒时间分辨荧光技术的发展、现状。相比其他检测环境中多环芳烃的方法、手段,结合激光诱导纳秒时间分辨荧光技术在实际工作中的应用,评述其在检测实际环境中多环芳烃方面的应用优势、潜力及前景展望。     

A novel smooth impact drive mechanism actuation method with dual-slider for a compact zoom lens system

In this paper, a novel actuation method for a smooth impact drive mechanism that positions dual-slider by a single piezo-element is introduced and applied to a compact zoom lens system. A mode chart that determines the state of the slider at the expansion or shrinkage periods of the piezo-element is presented, and the design guide of a driving input profile is proposed. The motion of dual-slider holding lenses is analyzed at each mode, and proper modes for zoom functions are selected for the purpose of positioning two lenses. Because the proposed actuation method allows independent movement of two lenses by a single piezo-element, the zoom lens system can be designed to be compact. For a feasibility test, a lens system composed of an afocal zoom system and a focusing lens was developed, and the passive auto-focus method was implemented.     

A compact semiconductor opening swith-based generator with a 300-kV output voltage and up to 2-kHz pulse repetition rate

A compact generator with a semiconductor opening switch (SOS-diode) shaping across resistive load pulses with an amplitude of up to 300 kV, duration of 30–50 ns, and a 300-Hz pulse repetition under uninterrupted operation and up to 2 kHz in a 30-s burst mode is described. The generator contains a thyristor charging device, magnetic compressor, and inductive storage with a semiconductor opening swith based on SOS-diodes. The average output power at a maximum pulse repetition rate and a 250kV-voltage is 16 kW. The overall dimensions of the generator are 0.85×0.65×0.42 m, the weight is about 115 kg.