Recent theoretical and experimental studies indicated that at certain conditions surface plasmon oscillations (SPOs) may
show non-classical properties. In this study we present the results of our measurements on spatial distribution and photon
statistics of the light emitted by surface plasmon oscillations. Both visible and near infrared lasers have been used for
generation of surface plasmons. The experiments were performed in the Kretschmann geometry using both gold and
silver layers at several laser pumping powers. We used different type of photo detectors in the photon counting regime to
measure the statistical properties of the light generated by surface plasmons. The photon statistics have been measured
by different methods. Time interval statistics, photon-number distribution and correlation function of the generated light
were determined and compared to those of the exciting laser. Correlations between statistical properties of the light
emitted by decaying surface plasmons and the exciting laser source have been studied.
We have developed our pervious experimental setup using correlated photon pairs (to the calibration of photo detectors) to realize a controllable photon source. For the generation of such photon pairs we use the non-linear process of parametric down conversion. When a photon of the pump beam is incident to a nonlinear crystal with phase matching condition, a pair of photons (signal and idler) is created at the same time with certain probability. We detect the photons in the signal beam with a single photon counting module (SPCM), while delaying those in the idler beam. Recently we have developed a fast electronic unit to control an optical shutter (a Pockels cell) placed to the optical output of the idler beam. When we detect a signal photon with the controlling electronic unit we are also able to open or close the fast optical shutter. Thus we can control which idler photons can propagate through the Pockels cell. So with this photon source we are able to program the number of photons in a certain time window. This controllable photon source that is able to generate a known number of photons with specified wavelength, direction, and polarization could be useful for applications in high-accuracy optical characterisation of photometric devices at the ultra-low intensities. This light source can also serve as a standard in testing of optical image intensifiers, night vision devices, and in the accurate measurement of spectral distribution of transmission and absorption in optical materials.
We designed a special light source generating a pre-determined number of photons taking advantage of our previous experimental results and calculations that establish a new approach to the calibration of photodetectors and determination of the absolute value of quantum efficiency of photon-counting photomultipliers using a single detector and entangled-photon pairs. This source is capable of generating a known number of photons of specified wavelength, in specified direction, and polarization for high-accuracy optical measurements (optical metrology) at the ultra-low intensities. The design and the modeling have been performed taking into account the main time characteristics of electronics, efficiency of detectors, parameters of the signal, losses, etc. The data evaluation system has been designed and tested; the assembly of the experimental set-up has been performed. Main parts of the optical and electronic system (generation of photon pairs, detectors, Pockels cells, etc.) have been tested. Such light source can be successfully applied in different areas of optical metrology, especially in photometry.
A photon correlation LDA system for the simultaneous measurement of sub-micrometer particle size and velocity is introduced. Following the results of Monte Carlo simulations it is shown that the FFT of the auto-correlation function of the detected scattered intensity contains the information on particle size. Experimental results on polystiren latex particles of 100 nanometer size are discussed.
KEYWORDS: Particles, Signal detection, Laser development, Control systems, Calibration, Liquids, Optimization (mathematics), High dynamic range imaging, Electronic filtering, Spherical lenses
A new liquid-borne particle counter is described that utilizes an optimized optical setup to determine the size distribution and concentration by two different methods and to estimate the shape-factor of the suspended particles. The aim of this optimization was to achieve the appropriate optical conditions for such type of measurement, viz. determining the geometry of the illumination and detection, and calculating the testing volume and dependence of the parameters of detected signal on the particle size for pulse height and pulse duration methods performed at the same illumination and detection conditions. The main benefit of the developed device is the high dynamic range of the size determination of the micron-size liquid-borne particles and the possibility of estimating their shape-factor. The proposed measurement method was incorporated in a PC- controlled LQB-1-200-L-T liquid-borne laser particle counter developed on the basis of our previous APC-03-2 and APC-03- 2A air-borne particle counters and a LQB-1-200 liquid-borne particle counter.
We propose the measurement of particle size, which is based on the visibility measurement of the pre-detection signal corresponding to particle transit of the sensing volume in a photon correlation LDA arrangement. It is shown that a good estimate of the visibility is the ratio of the contents of two specific channels of the Fourier transform of the autocorrelation function. We show that in a wide range of experimental conditions this ratio is a monotonous function of particle size. This circumstance leads to the possibility of defining calibration curves for practical devices.
An existence of pairs of rigorously correlated photons (biphotons) from nonlinear parametric down conversion has made it possible to develop a technique for measuring the absolute value of quantum efficiency of the optical detectors, both in photon-counting and in analog regimes, without using any standard light sources. A new technique for the measurement of quantum efficiency using single photomultiplier was evaluated. It is based on the measurement of the ratio between the single- and double- electron peaks in its pulse-height distribution.
Several proposals are known for the simultaneous measurement of particle velocities and size. In this study we propose to measure the ratio of the contents of two specific channels of the Fourier transform of the autocorrelation function of the pre-detection signal corresponding to single particle transit of the sensing volume. We show that in a wide range of experimental conditions this ratio is a monotonous function of particle size. This circumstance leads to the possibility of defining calibration curves for practical devices.
A new liquid-borne particle counter is described that utilizes an optimized optical set-up to determine the size distribution and concentration by two different methods and to estimate the shape-factor of the suspended particles. The aim of this optimization was to achieve the appropriate optical conditions for such type of measurement, viz. determining the geometry of the illumination and detection, and calculating the testing volume and dependence of the parameters of detected signal on the particle size for pulse height and pulse duration methods performed at the same illumination and detection conditions. The possibility of estimating the shape-factor of micron-size particles is discussed. The proposed measurement method was incorporated in a PC-controlled LQB-1-200-L-T liquid-borne laser particle counter developed on the basis of previous APC- 03-2 and APC-03-2A air-borne particle counters and a LQB-1-200 liquid-borne particle counter.
A pair of rigorously correlated photons (biphotons) from parametric down conversion makes it possible to use them for measuring the absolute value of the quantum efficiency of the optical detectors, both in photon counting and in analog regimes, that does not use any calibrated standard light sources. Using this method the quantum efficiency of EG&G avalanche photodetectors was determined.
KEYWORDS: Particles, Signal detection, Liquids, High dynamic range imaging, Calibration, Laser development, Sensors, Semiconductor lasers, Light scattering, Control systems
A new liquid-borne particle counters is described that utilizes an optimized optical set-up to determine the size distribution and concentration by two different methods and to estimate the shape-factor of the suspended particles. The aim of this optimization was to achieve the appropriate optical conditions for such type of measurement, viz. determining the geometry of the illumination and detection, and calculating the testing volume and dependence of the parameters of detected signal on the particle size for pulse height and pulse duration methods performed at the same illumination and detection conditions. The main benefit of the developed device is the high dynamic range of the size determination of the micron-size liquid-borne particles and the possibility of estimating their shape-factor. The proposed measurement method was incorporated in a PC- controlled LQB-1-200-L-T liquid-borne laser particle counter developed on the basis of previous APC-03-2 and APC-03-2A air-borne particle counters and a LQB-1-200 liquid-borne particle counter.
Several methods (particle counting and sizing, (beta) -ray absorption monitoring, gravimetric measurements, microscopy) were all applied to study the airborne dust particle pollution in Budapest, at various locations and during different seasons of the year. In addition, the airborne dust particle concentration was determined at several altitudes and several locations as a function of particle size. The results obtained by different measurements demonstrate that in certain cases the measured pollution exceeded the values permitted by Hungarian health standards.
A light-scattering airborne particle counter with a new optical design having the optical sampling chamber outside the laser resonator is presented. This device can be used to measure the size distribution of particles from a diameter of 0.3 μm in a wide concentration range with high reliability and stability. Some results of the applications of the device in highly contaminated environments are reviewed.
KEYWORDS: Signal detection, Sensors, Interferometers, Heterodyning, Signal processing, Data acquisition, Motion analysis, Analog electronics, Resolution enhancement technologies, Motion measurement
The development of a data acquisition system for a high resolution motion analyzer is discussed. The displacement measurement is based on a Michelson-type heterodyne interlerometer. The gained detector signals of the interferometer are processed by the direct phase comparison method. This method makes it possible to achieve a resolution equivalent of 1/512 of the applied optical wavelength, without the intricate signal conditioning needed by the commonly used phase-locked loop frequency multiplication or analog signal multiplication methods. The main technical data of the system are 1.25-nm resolution, 20-m measuring distance, and 60-kHz sample rate. The accuracy is better than ± 10 nm ± 0.1 ppm within a velocity range of ± 1.8 m/s and an acceleration range of ± 9900 m/s2.
We discuss the design and estimated accuracy of a multi-axis Michelson-type heterodyne interferometer system with the following main technical data: nominal system resolution 1.25nm, measuring distance 20m, maximum sampling rate 60kHz. We show that the accuracy associated with the data acquisition system is better than ±10nm+0.1ppm within the velocity range of ±1.8m/s and acceleration range of ±9900 m/s2 . Effects of the optical frequency cross talk due to non ideal beam separation, which limits the measurement accuracy are considered.
The increased safety regulations in nuclear power stations require the development of new, highly automated and remote controlled procedures, especially in the Eastern European countries where the original design did not provided the required safety. Our group has developed and installed a novel telemetric position sensing equipment in the nuclear power station of Paks, for the accurate monitoring of the crane position during reactor maintenance. The equipment utilises high resolution line scan cameras and special bar-codes.
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