Ultrafast Surface Plasmon Probing of Interband and Intraband Hot Electron Excitations.

Upon the interaction of light with metals, nonthermal electrons are generated with intriguing transient behavior. Here, we present femtosecond hot electron probing in a noveloptical pump/plasmon probe scheme. With this, we probed ultrafast interband and intraband dynamics with 15 nm interface selectivity, observing a two-component-decay of hot electron populations. Results are in good agreement with a three-temperature model of the metal; thus, we could attribute the fast (∼100 fs) decay to the thermalization of hot electrons and the slow (picosecond) decay to electron-lattice thermalization. Moreover, we could modulate the transmission of our plasmonic channel with ∼40% depth, hinting at the possibility of ultrafast information processing applications with plasmonic signals.

Few-Cycle Surface Plasmon Polaritons.

Surface plasmon polaritons (SPPs) can confine and guide light in nanometer volumes and are ideal tools for achieving electric field enhancement and the construction of nanophotonic circuitry. The realization of the highest field strengths and fastest switching requires confinement also in the temporal domain. Here, we demonstrate a tapered plasmonic waveguide with an optimized grating structure that supports few-cycle surface plasmon polaritons with >70 THz bandwidth while achieving >50% light-field-to-plasmon coupling efficiency. This enables us to observe the─to our knowledge─shortest reported SPP wavepackets. Using time-resolved photoelectron microscopy with suboptical-wavelength spatial and sub-10 fs temporal resolution, we provide full spatiotemporal imaging of co- and counter-propagating few-cycle SPP wavepackets along tapered plasmonic waveguides. By comparing their propagation, we track the evolution of the laser-plasmon phase, which can be controlled via the coupling conditions.

Three-photon and four-photon absorption in lithium niobate measured by the Z-scan technique.

Open-aperture Z-scan measurements have been carried out to investigate the three-photon (3 PA) and four-photon absorption (4 PA) coefficients at 800 nm and 1030 nm wavelengths, respectively in congruent and stoichiometric lithium niobate (cLN, sLN) with different concentrations of Mg doping. The laser pulse duration at the two wavelengths were 40 and 190 fs. The peak intensity inside the crystals varied between approximately 110 and 550 GW/cm2. The 3 PA and 4 PA coefficients were evaluated using a theoretical model and the results suggest that their minima are at or around the Mg doping level corresponding to the threshold for suppressing photo-refraction for both cLN and sLN. This result can be attributed to the contribution of crystal defects to the 3 PA and 4 PA processes. Furthermore, the 4 PA at 1030 nm exhibited greater nonlinear absorption than the 3 PA at 800 nm under the same intensity level. Possible reasons for this unexpected behavior are discussed. Overall, comparing the 3 PA and 4 PA values of these crystals will enable for selection of the optimum composition of LN crystal for efficient THz generation and for other nonlinear optical processes requiring high pump intensities.

A potentially new thromboembolic event scoring system in polycythaemia vera patients: An audit of the Hungarian Philadelphia negative chronic myeloproliferative neoplasia register.

OBJECTIVE: The Hungarian National Registry for Philadelphia chromosome negative myeloproliferative neoplasms was used to analyse the thromboembolic events (TE) of Hungarian patients with polycythemia vera (PV). METHODS: Data from 351 JAK2 V617F-positive patients diagnosed with PV were collected online from 15 haematology centres reporting clinical characteristics, therapeutic interventions and thromboembolic events. TE events were evaluated before and after diagnosis based upon the Landolfi and Tefferi risk assessment scales. RESULTS: TE were reported on 102 patients before diagnosis and 100 during the follow-up period. Comparing to the frequency of major arterial events before PV diagnosis, we can notice a decreasing tendency after diagnosis: from 12.3% to 2.6% (p < .00003). There was no significant change in the rate of major venous events (from 5.1% to 8.5%; p = .1134) or minor arterial events (from 11.7% to 17.4%; p = .073). Bleeding events were recorded in 5.7% of patients. Despite treatment with HU + ASA, 44 patients (43.1%) with prior TE had recurrent thromboembolic complications. The particular analysis of our data revealed a new TE scoring system based on: age, gender, previous TE and iron deficiency at the time of diagnosis. CONCLUSIONS: Our registry enables characterisation of patients with PV. The high level of recurrent TE events highlights the need for more effective and risk-adapted therapy.

Nonadiabatic Nano-optical Tunneling of Photoelectrons in Plasmonic Near-Fields.

Nonadiabatic nano-optical electron tunneling in the transition region between multiphoton-induced emission and adiabatic tunnel emission is explored in the near-field of plasmonic nanostructures. For Keldysh γ values between ∼1.3 and ∼2.2, measured photoemission spectra show strong-field recollision driven by the nanoscale near-field. At the same time, the photoemission yield shows an intensity scaling with a constant nonlinearity, which is characteristic for multiphoton-induced emission. Our observations in this transition region were well reproduced with the numerical solution of Schrödinger's equation, mimicking the nanoscale geometry of the field. This way, we determined the boundaries and nature of nonadiabatic tunneling photoemission, building on a key advantage of a nanoplasmonic system, namely, that high-field-driven recollision events and their signature in the photoemission spectrum can be observed more efficiently due to significant nanoplasmonic field enhancement factors.

Femtosecond LIPSS on indium-tin-oxide thin films at IR wavelengths.

We investigated laser-induced periodic surface structures (LIPSS) generated on indium-tin-oxide thin films with femtosecond laser pulses in the infrared region. Using pulses between 1.6 and 2.4 µm central wavelengths, we observed robust LIPSS morphologies with a periodicity close to λ/10. Supporting finite-difference time-domain calculations suggests that the surface forms are rooted in the field localization in the surface pits leading to a periodically increased absorption of the laser pulse energy that creates the observed periodic structures.

Anagrelide influences thrombotic risk, and prolongs progression-free and overall survival in essential thrombocythaemia vs hydroxyurea plus aspirin.

OBJECTIVE: We report an extension study of patients with essential thrombocythaemia (ET) in the Hungarian Myeloproliferative Neoplasm (HUMYPRON) Registry, which demonstrated that over 6 years anagrelide significantly decreased the number of patients experiencing minor arterial and minor venous thrombotic events (TEs) vs hydroxyurea+aspirin. METHODS: Data on patients with ET were collected through completion of a questionnaire developed according to 2008 WHO diagnostic criteria and with regard to Landolfi, Tefferi and IPSET criteria for thrombotic risk. Data were entered into the registry from 14 haematological centres. TEs, secondary malignancies, disease progression and survival were compared between patients with ET treated with anagrelide (n = 116) and with hydroxyurea+aspirin (n = 121). RESULTS: Patients were followed for (median) 10 years. A between-group difference in the number of patients with TEs was observed (25.9% anagrelide vs 38.0% hydroxyurea+aspirin; P = .052). Minor arterial events were more frequently reported in the hydroxyurea+aspirin group (P < .001); there were marginally more reports of major arterial events in the anagrelide group (P = .049). TE prior to diagnosis was found to significantly influence TE incidence (P > .001). Progression-free survival (P = .004) and survival (P = .001) were significantly increased for the anagrelide group vs hydroxyurea+aspirin. CONCLUSIONS: Anagrelide reduced TEs, and increased progression-free and overall survival vs hydroxyurea+aspirin over (median) 10 years.

High harmonic generation on noble gas clusters.

High order harmonics (HHG) were generated on noble gas cluster targets with different cluster sizes. The independently characterized cluster sources enabled experimental investigation of the recombination mechanism. HHG spectra were recorded for different backing pressures and gases (Ar, Xe) as a function of driver pulse ellipticity. Since the ellipticity-dependent HHG decay is essentially the same for the different gas-pressure pairs, we can conclude that the recombination process is dominated by atom-to-itself recollisions irrespective of cluster size and material.

Ultrafast multipulse damage threshold of femtosecond high reflectors.

Laser-induced damage threshold is a fundamental figure of merit of femtosecond optical components used in large-scale laser systems. We tested a series of ultrafast mirrors featuring high band-gap dielectric materials as well as improved design and coating techniques. In a broad range of the damage test pulse train involving between 10 and 100,000 pulses (40 fs, 800 nm), pure dielectric high reflectors exhibit around 1.5 J/cm2 and hybrid Ag-multilayer mirrors can exhibit well above 1.2 J/cm2 damage threshold. In addition, a reference antireflection coating exceeded 2 J/cm2. Damage threshold dependence on the number of pulses was similar for all optics involved.

Measurement of Nanoplasmonic Field Enhancement with Ultrafast Photoemission.

Probing nanooptical near-fields is a major challenge in plasmonics. Here, we demonstrate an experimental method utilizing ultrafast photoemission from plasmonic nanostructures that is capable of probing the maximum nanoplasmonic field enhancement in any metallic surface environment. Directly measured field enhancement values for various samples are in good agreement with detailed finite-difference time-domain simulations. These results establish ultrafast plasmonic photoelectrons as versatile probes for nanoplasmonic near-fields.

Anagrelide reduces thrombotic risk in essential thrombocythaemia vs. hydroxyurea plus aspirin.

OBJECTIVE: To evaluate the reduction in thrombotic events (TE) in patients with essential thrombocythaemia (ET) treated with anagrelide versus hydroxyurea + aspirin (HU + ASA). METHODS: A questionnaire was developed using 2008 WHO diagnostic criteria, and thrombotic risk factors were stratified according to Landolfi criteria. Through questionnaire completion, clinicians at Hungarian haematological centres entered data into the Hungarian MPN Registry on patients with myeloproliferative neoplasms. Based on ET registry data, TEs in anagrelide-treated patients (n = 139) were compared with HU + ASA-treated patients (n = 141). RESULTS: Patients were followed up for (median) 6 yr. TEs were reported in significantly fewer anagrelide-treated patients versus HU + ASA (15.1% versus 49.6%; P < 0.001). Numbers of major arterial and major venous events were similar between the groups, although there were over fivefold more minor arterial and minor venous events in the HU + ASA group (P < 0.001). While median age at diagnosis was older and length of follow-up shorter in the HU + ASA group (P < 0.05), this did not influence TE incidence; medication and TE before diagnosis only influenced TE incidence. CONCLUSIONS: Anagrelide significantly decreased the number of patients experiencing minor arterial and minor venous TEs versus HU + ASA over 6 yr. Risk of TE after diagnosis was significantly increased if the patient had TE before diagnosis.

[An audit of the Hungarian Philadelphia negative chronic myeloproliferative neoplasia registry. Evaluation of the essential thrombocythaemic patients]. / Philadelphia-negatív krónikus Myeloproliferativ Neoplasia Magyarországi Regiszter. Essentialis thrombocythaemiás betegeink adatainak elemzése.

INTRODUCTION: In order to establish and use a national registry, several Hungarian hematology centers collected data of myeloproliferative neoplasia patients. AIM: The recent publication is an analysis of the data of registered essential thrombocythaemic patients. METHOD: an online electronic registry has been established, using 2008 World Health Organization's diagnostic criteria and thrombotic risk was evaluated according to Landolfi stratification. RESULTS: Data of 350 essential thrombocythaemic patients from 15 Hungarian hematology centers entered up to the date of June 30, 2015 were used for analysis. Patients were followed up to (median) 6 years. The epidemiologic data (age, gender) and thrombotic events prior and after the diagnosis, were similar to the literature. The thrombotic events of anagrelide treated patient (n = 139) and the hydroxyurea + aspirin treated patients (n = 141) have been compared. The major arterial and venous events were similar between the groups, but there were fivefold less minor arterial and venous events in the anagrelide group (p<0.001). Thrombotic incidence after diagnosis were influenced only by medication and thrombotic events before the diagnosis. CONCLUSIONS: Anagrelide significantly decreased the number of patients experiencing minor arterial and minor venous thrombosis, vs hydroxyurea + aspirin. Despite of the treatment the risk of thrombotic events after diagnosis remained high, and was significantly increased in patients with thrombosis before diagnosis. Orv. Hetil., 2017, 158(3), 111-116.

[Hungarian Philadelphia negative chronic myeloproliferative neoplasia registry. Evaluation of the Polycythemia vera patients]. / Philadelphia-negatív krónikus Myeloproliferativ Neoplasia Magyarországi Regiszter. Polycythaemia verás betegeink adatainak elemzése.

Intruduction and aim: The Hungarian National Registry for Philadelphia chromosome negative myeloproliferative neoplasms has been developed. The aim of the recent study is to assess the clinical characteristics of Hungarian patients with polycythemia vera. METHOD: Data of 351 JAK2V617F and exon 12 mutation positive polycythemia vera patients were collected online from 15 haematology centres reporting epidemiologic, clinical characteristics, diagnostic tools, therapeutic interventions, thromboembolic complications, disease transformations. Vascular events prior to and after diagnosis were evaluated upon the Landolfi risk assessment scale. RESULTS: 116 thromboembolic events were reported in 106 PV patients prior to diagnosis and 152 occasions in 102 patients during follow-up. The frequency of major arterial events were significantly reduced (p<0.0001) and the minor venous events were significantly elevated (p<0.0001) after the diagnosis. Major hemorrhagic complications were found in 25 and transformation in 26 cases. CONCLUSIONS: Our registry allows to collect and evaluate the features of patients with polycythemia vera. The Landolfi risk stratification was proven to be useful. Based on evaluated data, accuracy of diagnostic criteria and compliance to risk-adapted therapeutic guidelines are needed. Orv Hetil. 2017; 158(23): 901-909.

Femtosecond damage resistance of femtosecond multilayer and hybrid mirrors.

Improving the laser-induced damage threshold of optical components is a basic endeavor in femtosecond technology. By testing more than 30 different femtosecond mirrors with 42 fs laser pulses at 1 kHz repetition rate, we found that a combination of high-bandgap dielectric materials and improved design and coating techniques enable femtosecond multilayer damage thresholds exceeding 2 J/cm2 in some cases. A significant ×2.5 improvement in damage resistance can also be achieved for hybrid Ag-multilayer mirrors exhibiting more than 1 J/cm2 threshold with a clear anticorrelation between damage resistance and peak field strength in the stack. Slight dependence on femtosecond pulse length and substantial decrease for high (megahertz) repetition rates are also observed.

Ultrafast Electron Emission from a Sharp Metal Nanotaper Driven by Adiabatic Nanofocusing of Surface Plasmons.

We report photoelectron emission from the apex of a sharp gold nanotaper illuminated via grating coupling at a distance of 50 µm from the emission site with few-cycle near-infrared laser pulses. We find a fifty-fold increase in electron yield over that for direct apex illumination. Spatial localization of the electron emission to a nanometer-sized region is demonstrated by point-projection microscopic imaging of a silver nanowire. Our results reveal negligible plasmon-induced electron emission from the taper shaft and thus efficient nanofocusing of few-cycle plasmon wavepackets. This novel, remotely driven emission scheme offers a particularly compact source of ultrashort electron pulses of immediate interest for miniaturized electron microscopy and diffraction schemes with ultrahigh time resolution.

[Development of the registry for Philadelphia-negative chronic myeloproliferative neoplasia in Hungary]. / Philadelphia-negatív krónikus myeloproliferativ neoplasia regiszter magyarországi létrehozása.

INTRODUCTION: The establishment and operation of disease registry can be used to collect data on epidemiology cases. In addition, the registry can help to work out medical and health economical and political decisions for longer term. AIM: The aim of the authors was to collect and analyse data of patients with Philadelphia negative neoplasia in Hungary and draw conclusions about the basic types and features of the relevant disease. METHOD: An online electronic data collection system has been established, based on the permission of the Regional and Institutional Committee of Science and Research Ethics obtained in April 8, 2013. Data collection has been initiated by hematology centres in Hungary. In addition to collection of the epidemiologic data, blood and bone marrow analysis data have been collected, as well. Also, based on cardiovascular factors, risk stratification has been established. Finally, the authors have investigated the method and practice of patient treatment in Hungary. RESULTS: Data of 901 patients from 15 Hungarian haematology centres have been recorded up to the date of June 30, 2015. After clarification of the data, 426 polycythaemia vera, 350 essential thrombocythaemia and 82 myelofibrosis cases were used for analysis. CONCLUSIONS: An online registry has been established which helps to clarify and analyse the basic features of certain medical cases and their treatment in Hungary. Including additional medical centres could help to improve the accuracy of medical analysis.

[Low mean cell hemoglobin is a reliable marker for iron deficiency screening]. / Az alacsony átlagos vörösvértest-hemoglobin alkalmas a vashiány szurésére.

INTRODUCTION: Screening for iron deficiency, which affects a significant proportion of the population, is a burning issue in the health care system. AIM: The aim of the authors was to examine whether low mean cell hemoglobin concentration measured by automated hematology analyzers is a suitable screening parameter for iron deficiency. METHOD: The data for this study included a total of 247,705 complete blood counts and 10,840 tests with different parameters of iron metabolism. Patients were evaluated at Somogy County Kaposi Mór Teaching Hospital during a period of 30 months between January 1, 2013 and June 30, 2015. Low cell hemoglobin values were analyzed with iron metabolism parameters measured simultaneously. RESULTS: A total of 830 patients whose iron metabolism parameters were measured simultaneously had low mean cell hemoglobin (<28pg). Of the 830 patients, 679 (82%) had both low mean cell hemoglobin and iron deficiency, while in 126 hemodialysed patients (15%), 8 patients with myelofibrosis, and 5 patients with rheumatic arthritis had low mean cell hemoglobin without iron deficiency. In the remaining 6 patients the cause of low mean cell hemoglobin or iron deficiency was not identified. CONCLUSIONS: Based on these findings the authors conclude that mean cell hemoglobin may be a reliable screening marker for iron deficiency.

Conversion of chirp in fiber compression.

Focusing positively chirped femtosecond pulses into nonlinear fibers provides significant spectral broadening and compression at higher pulse energies than achievable conventionally because self-focusing and damage are avoided. Here, we investigate the transfer of input to output chirp in such an arrangement. Our measurements show that the group delay dispersion of the output pulse, originating from the nonlinearities, is considerably reduced as compared to the initial value, by about a factor of 10. The mechanism of chirp reduction is understood by an interplay of self-phase modulation with initial chirp within the fiber. A simple model calculation based on this picture yields satisfactory agreement with the observations and predicts significant chirp reduction for input pulses up to the µJ regime. In practice, the reduction of chirp observed here allows for compressing the spectrally broadened intense pulses by ultrabroadband dispersive multilayer mirrors of quite moderate dispersion.

Design of high-efficiency ultrabroadband dielectric gratings.

We present a design concept of dielectric gratings containing resonant high (TiO2) and resonant low (SiO2) index dielectric thin-film layers between the grating and the underlying multilayer reflector. We use numerical simulations and the genetic algorithm optimization method to achieve high diffraction efficiency (>97%) in the first diffracted order over a wide wavelength range (∼160 nm) at around 800 nm. The basic concept of the structural optimization contains a high refractive index binary grating with alternating low- and high-index reflector layers, the thicknesses of which are also among the optimization parameters. We introduce two resonant dielectric layers directly below the corrugated TiO2 grating structure and we choose a small (<10%) filling fraction for the grating. This concept allows us to broaden the spectral range where high DE can be achieved. We investigate here gratings for both Littrow-mount and off-Littrow applications.

Ultrafast strong-field photoemission from plasmonic nanoparticles.

We demonstrate the ultrafast generation of electrons from tailored metallic nanoparticles and unravel the role of plasmonic field enhancement in this process by comparing resonant and off-resonant particles, as well as different particle geometries. We find that electrons become strongly accelerated within the evanescent fields of the plasmonic nanoparticles and escape along straight trajectories with orientations governed by the particle geometry. These results establish plasmonic nanoparticles as versatile ultrafast, nanoscopic sources of electrons.