D. Ponikvar

University of Ljubljana · Faculty of Mathematics and Physics

We observe dark-state polariton collapses and revivals in a quantum memory based on electromagnetically induced transparency on a cloud of cold cesium atoms in a magnetic field. Using σ+-polarized signal and control beams in the direction of the magnetic field, we suppress the dark-state polariton collapses by polarizing the atoms towards one of th...

The aim of this study is to evaluate the method for the compensation of magnetic field interference from the mains, which consists primarily of components with a frequency of 50 (60) Hz and its multiples. The setup compensates for the interfering field using three Helmholtz coils, magnetic field sensors, a digital processing unit, and power amplifi...

We observe dark-state polariton collapses and revivals in a quantum memory based on electromagnetically induced transparency on a cloud of cold cesium atoms in a magnetic field. Using $\sigma^+$ polarized signal and control beams in the direction of the magnetic field, we suppress the dark-state polariton collapses by polarizing the atoms towards o...

An experiment on temperature regulation was prepared and is regularly conducted in a laboratory course on electronic at the faculty level. The experiment demonstrates the use, problems and solutions with feedback introduced for temperature regulation. The plans for hardware and complete software to run the experiment are freely available at author’...

We combine the Ramsey interferometry protocol, the Stern-Gerlach detection scheme, and the use of elongated geometry of a cloud of fully polarized cold cesium atoms to measure the selected component of the magnetic-field gradient along the atomic cloud in a single shot. In contrast to the standard method where the precession of two spatially separa...

We combine the Ramsey interferometry protocol, the Stern-Gerlach detection scheme, and the use of elongated geometry of a cloud of fully polarized cold cesium atoms to measure the selected component of the magnetic field gradient along the atomic cloud in a single shot. In contrast to the standard method where the precession of two spatially separa...

A design of a low-cost electrical pulse generator capable of producing random pulses with exponentially decaying tail as coming from a nuclear detector is described. The generator can generate periodic single or double pulses of a user-defined amplitude and decay time, or randomly occurring pulses with amplitudes drawn at random from a user-prescri...

A compact portable aerosol sampling and measurement device was developed at Jožef Stefan Institute (JSI). A CeBr3 scintillation detector is positioned centrally within a concertinaed filter assembly. It provides continuous and via network communications on-line monitoring of low levels of airborne radioactive particulates.. The evaluation of the re...

In the frame of the European metrological research project MetroERM, a compact portable aerosol sampling and measurement device was developed at Jožef Stefan Institute. The system incorporates a CeBr3 scintillation detector positioned centrally within a concertinaed filter assembly and an improved high flow rate air pump. It provides continuous on-...

Optical observations provide convincing evidence that the optical phase of the Crab pulsar follows the radio one closely. Since optical data do not depend on dispersion measure variations, they provide a robust and independent confirmation of the radio timing solution. The aim of this paper is to find a global mathematical description of Crab pulsa...

A new concept of the LCD light-switching optical filter allowing for very high, electrically controlled, continuously variable light attenuation (up to ≧100,000) optimized/symmetrized for the light incidence along the normal to the LCD plane is proposed. The new LCD light-switching optical filter also exhibits very low light attenuation dependence...

An electronic circuit for generation of short light pulses is presented. The circuit uses low-cost, general-purpose electronic components and is simple in its structure. It is suitable for testing of the instruments and setups for the detection of light and adjusting correct timing and synchronization. The light pulses have a full width at half-max...

We observed the Crab pulsar in October 2008 at the Copernico Telescope in Asiago - Cima Ekar with the optical photon counter Aqueye (the Asiago Quantum Eye) which has the best temporal resolution and accuracy ever achieved in the optical domain (hundreds of picoseconds). Our goal was to perform a detailed analysis of the optical period and phase dr...

We are developing fast photon-counter instruments to study the rapid variability of astrophysical sources by time tagging photon arrival times with unprecedented accuracy, making use of a Rubidium clock and GPS receiver. The first realization of such optical photon-counters, dubbed AquEYE (the Asiago Quantum Eye), was mounted in 2008 at the 182 cm...

A rotating magnetic field is the basis for the transformation of electrical energy to mechanical energy. School experiments on the rotating magnetic field are rare since they require the use of specially prepared mechanical setups and/or relatively large, three-phase power supplies to achieve strong magnetic fields. This paper proposes several expe...

Two similar experiments on conservation of energy and transformation of mechanical into electrical energy are presented. Both can be used in classes, as they offer numerous possibilities for discussion with students and are simple to perform. Results are presented and are precise within 20% for the version of the experiment where measured values ar...

We present a novel concept of a wide viewing angle liquid-crystal display (LCD) light shutter, taking advantage of the highly symmetric 180 degrees -twisted liquid-crystal (LC) configuration and the light propagation starting with a single mode. In a specific case of the high voltage driven LCD light shutter, the resulting very high overall symmetr...

This paper describes the measurement of an ac magnetic field of a wire using a pick-up coil, a personal computer and a soundcard. No other equipment is needed to evaluate the field. The program is freeware, available at the author's web site. Several experiments with results suitable for undergraduate student labs are presented.

The paper presents a novel concept of a wide viewing angle LCD light filter, making advantage of the symmetric, highly-twisted complementary dual LC-cell configuration. The resulting overall symmetry allows for very high, continuously variable optical attenuation as well as efficient angular compensation using just simple, cheap negative-birefringe...

A novel liquid crystal display (LCD) driving concept for light shutters is shown here, based on driving signal polarity reversal controlled by the driving voltage integral across the LCD switching element electrodes, as opposed to plain periodic polarity reversal. This driving scheme optimizes the DC driving signal voltage balancing and guarantees...

A novel liquid crystal display (LCD) driving concept for light shutters is presented, based on the driving signal polarity reversal controlled by the driving voltage integral across the LCD switching element electrodes, as opposed to plain periodic polarity reversal. This driving scheme optimizes the DC driving signal voltage balancing and guarante...

The paper presents a novel concept of a wide viewing angle LCD light shutter, making advantage of the highly symmetric 180°-twisted LC-configuration and ordinary mode of the light propagation. The resulting very high overall symmetry allows for efficient angular compensation using just a simple negative-birefringent c-plate retarder.

The performance of a high-resolution spectroscopy system is affected by the noise properties of the spectroscopy amplifier. A new approach for measurement of the noise at the output of the spectroscopy amplifier is presented.

A novel liquid crystal display (LCD) driving concept for light shutters is shown here, based on driving signal polarity reversal controlled by the driving voltage integral across the LCD switching element electrodes, as opposed to plain periodic polarity reversal. This driving scheme optimizes the DC driving signal voltage balancing and guarantees...

A simple driving system for generating photons with flat energy spectrum by the Doppler effect is described. The classical double-loudspeaker design with electronic feedback is replaced with a single loudspeaker and smart driving electronics, that uses low cost microcontrollers and DACs.

The apparatus described uses polarized light to trace the rotation angle of an object. The result of the measurement does not depend on the distance between the object and the base surface within a wide range, and the resolution is better than 0.25° with the full range of 180°. There are no electrical contacts to the rotating object.

Two types of ADCs are used in nuclear spectroscopy. These are the Wilkinson-type ADC and the successive approximation ADC. The Wilkinson-type ADCs are superior in channel profile and differential linearity over successive approximation ADCs. They are, however, relatively slow. The design presented joins the best from both: fast conversion time comb...

Dead time correction algorithms are implemented in spectroscopy systems. They reduce errors in the determination of the rate of incoming pulses. An improvement of a known dead time correction algorithm is presented. The improvement is supported by results of simulation.

The described random pulse generator produces TTL compatible pulses, random in time. The rate of the pulses can be preset to different values from 2500 to 100000 s-1 in steps of 2500 s-1. The rate is controlled by a quartz crystal. Minimum time interval between two successive random pulses is 97.6 ns. The generator was designed for testing and cali...