Search results for "Instrumentation"
showing 10 items of 4914 documents
Study of upconversion in highly Er-doped photonic crystal fibers through laser-transient dynamics
2014
The dynamic response after pump switch-on of a 980 nm pumped-ring laser based on an active photonic crystal fiber with an Er3+ ion concentration of ≈1020 ions cm−3 was registered. Then a numerical fitting procedure of a theoretical model was followed to the experimental values of the relaxation oscillation parameters as a function of the input pump power. Non-radiative energy-transfer mechanisms’ coefficients: homogeneous upconversion coefficient (Cup) and critical radii for upconversion (Ru) and migration (Rm) were determined. The calculated best-fit coefficients (Cup = 1.3 × 10−24 m3 s−1, Ru = 9 × 10−10 m, Rm = 13 × 10−10 m) were compared to those obtained with other steady-state an…
Femtosecond time-resolved photoemission electron microscopy operated at sample illumination from the rear side
2019
We present an advanced experimental setup for time-resolved photoemission electron microscopy (PEEM) with sub-20 fs resolution, which allows for normal incidence and highly local sample excitation with ultrashort laser pulses. The scheme makes use of a sample rear side illumination geometry that enables us to confine the sample illumination spot to a diameter as small as 6 μm. We demonstrate an operation mode in which the spatiotemporal dynamics following a highly local excitation of the sample is globally probed with a laser pulse illuminating the sample from the front side. Furthermore, we show that the scheme can also be operated in a time-resolved normal incidence two-photon PEEM mode w…
Impact of root canal preparation size and taper on coronal-apical micro-leakage using glucose penetration method
2014
Objectives: The purpose of this in vitro study was to assess the effect of root canal preparation size and taper on the amounts of glucose penetration. Material and Methods: For conducting this experimental study, eighty mandibular premolars with single straight canals were divided randomly into 2 experimental groups of 30 samples each and 2 control groups. Using K-files and the balance force technique, canals in group 1 were prepared apically to size 25 and coronally to size 2 Peeso - reamer. Group 2 were instrumented apically and coronally to size 40 and size 6 Peesoreamer, respectively. Rotary instrumentation was accomplished in group 1; using size 25 and .04 tapered and in group 2, size…
Probing large area surface plasmon interference in thin metal films using photon scanning tunneling microscopy.
2003
Abstract The interference of surface plasmons can provide important information regarding the surface features of the hosting thin metal film. We present an investigation of the interference of optically excited surface plasmons in the Kretschmann configuration in the visible spectrum. Large area surface plasmon interference regions are generated at several wavelengths and imaged with the photon scanning tunneling microscope. Furthermore, we discuss the non-retarded dispersion relations for the surface plasmons in the probe–metal system modeled as confocal hyperboloids of revolution in the spheroidal coordinate systems.
Selective growth and optical properties of sputtered BaTiO3films
2000
we report the growth of BaTiO 3 thin films by standard Radio Frequency sputtering. Without any in situ or post annealing, these polycristalline films are oriented relative to the substrate even when it is amorphous. We show that this preferential orientation may be monitored using a DC Bias during the film growth. At room temperature, cubic films of (100) and (110) orientations have been achieved, on fused silica substrate. Some optical waveguiding properties of these films have been studied. The resulting film index is 2.26 and the optical step index at the substrate interface is sharp. This allows the use of standard RF sputtering techniques to monitor oriented BaTiO 3 films for linear op…
Ion production from solid state laser ion sources.
2010
Laser ion sources based on resonant excitation and ionization of atoms are well-established tools for selective and efficient production of radioactive ion beams. Recent developments are focused on the use of the state-of-the-art all solid-state laser systems. To date, 35 elements of the periodic table are available from laser ion sources based on tunable Ti:sapphire lasers. Recent progress in this field regarding the establishment of suitable optical excitation schemes for Ti:sapphire lasers are reported.
Transconductance Converters Based on Current Mirrors Applied to pH Measurement Using ISFET Sensors
2009
New transconductance circuits (V/I converters) are designed based on current mirrors and operational amplifiers. Their input/output characteristics and the influence of DC parameters are obtained. Experimental results were performed, comparing them with the simulated results. An electronic instrumentation circuit is designed based on one of the transconductance converters analyzed. The purpose of this circuit was to condition the response of an ion-sensitive field-effect transistor (ISFET) to measure pH. In the proposed application, the V/I converter presented provides the stability and accuracy of the ISFET operating point, making an easy characterization procedure and the design of multic…
Extended gate electrode arrays for extracellular signal recordings
2000
Abstract We have fabricated arrays of planar gold electrodes arranged in a matrix of 8×8 with active areas ranging from 6 to 30 μm in diameter. An electronic amplification circuitry based on commercial junction field-effect transistors was used where the gold sensor fields act as extended gate electrodes (EGE) of the transistors, which leads to a new approach for long-term extracellular recording systems in vitro. The high input resistance of the amplification circuitry allows the use of small planar bare gold electrodes without further modification which therefore extends the frequency range of the measuring set-up down to the DC-level. The performance of our recording system has been test…
Note: Simultaneous modulation transfer spectroscopy on transitions of multiple atomic species for compact laser frequency reference modules
2018
We present a technique for simultaneous laser frequency stabilization on transitions of multiple atomic species with a single optical setup. The method is based on modulation transfer spectroscopy, and the signals are separated by modulating at different frequencies and electronically filtered. As a proof of concept, we demonstrate simultaneous spectroscopy of the potassium D1, D2 and rubidium D2 transitions. The technique can be extended in principle to other atomic species given the availability of optics and cells and allows the development of versatile and compact frequency reference modules.