Dániel Oszetzky

Quantum metal optics

Experimental and theoretical studies of the statistical properties of surface plasmon polaritons (SPOs) are described. Both classical and non-classical properties of surface plasmons are analysed. The temporal statistical behaviour at low excitation level, as measured by detecting the SPO emitted photon statistics as expressed by the correlation function and the temporal photon count distribution, show that the SPOs preserve the photon statistics of the laser. In the spatial distribution of the plasmon field as measured by an STM, squeezing, i.e. non-classical properties, were found. Independent simple model calculations confirmed the existence of both enhanced EM fields of surface plasmons and their squeezed character.

Designing a special light source with predetermined number of photons

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.

Pre-excitation studies for rubidium-plasma generation

The key element in the Proton-Driven-Plasma-Wake-Field-Accelerator (PWFA) project is the generation of highly uniform plasma from Rubidium vapor. A scientifically straightforward, yet highly challenging way to achieve full ionization is to use high power laser which can assure the barrier suppression ionization (BSI) along the 10 m long active region. The Wigner-team in Budapest is investigating an alternative way of uniform plasma generation. The proposed Resonance Enhanced Multi-Photon Ionization (REMPI) scheme can be probably realized by much less laser power. In the following we plan to investigate the resonant pre-excitations of the Rb atoms, both theoretically and experimentally. In the following our theoretical framework is presented together with the status report about the preparatory work of the planned experiment.

Surface plasmons and photon statistics

Statistical properties of photons emitted by decaying surface plasmons were studied by different methods. Time interval statistics, photon-number distribution and correlation function of the generated plasmons were determined and compared to those of the exciting laser. The coincidence of the measured distributions corresponding to laser light and photons generated by plasmons shows the same statistical behaviour for these two cases.

Controllable photon source

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.

Application of Correlated Photon Pairs in Optical Metrology

In this overview we present several metrological applications of the correlated photon pairs in characterizing of photodetectors — determination of the absolute value of the quantum efficiency using two detectors and a single detector technique —, measurement of the refractive index of fluids. We describe also a technique for creation a special photon source with the preprogrammed number of photons and propose a new method for determination of the optical quality of the crystal in which the parametric down-conversion is performed.

Femtosecond damage threshold at kHz and MHz pulse repetition rates

Femtosecond laser-induced damage threshold (LIDT) measurements for different optical components are well studied for a set of laser pulse repetition rates spanning the range between 1 Hz and 1 kHz. Recent years saw the advent of high-repetition-rate femtosecond systems with relatively high pulse energy. Therefore investigation of LIDT in the MHz region is essential. We performed several comparative femtosecond LIDT measurements on typically used ultrafast optical elements with different Ti:Sapphire laser systems having substantially different pulse repetition rates (a 1 kHz regenerative amplifier and a 4.3 MHz long-cavity oscillator) and found a substantially lower MHz LIDT threshhold.

Photon Statistic Measurements of Surface Plasmon Excitation

In this study we present the results of our measurements on photon statistic distributions of the light emitted by surface plasmon oscillations. Time interval statistics, photon-number distribution, auto-correlation and cross-correlation functions of the generated light were determined and compared to those of the exciting laser.

Hanbury Brown–Twiss type correlations with surface plasmon light

Intensity–intensity correlations are studied for light signals stemming from the spontaneous decay of surface plasmon oscillations, generated in the Kretschmann geometry. Non-classical photon statistics and the transition from antibunching to bunching of the electron counts have been found experimentally and analysed on a new theoretical basis.

Development of a high resolution interferometric system for testing the optical elements in ELI

The development and application of a phase shifting interferometric system for testing optical surfaces is described. Several application examples of this instrument for 3D surface topography diagnostics are presented. After certain expedient reconstruction the system can be used for testing the optical elements and different coatings in ELI (Extreme Light Infrastructure).