Fényhullámhosszon és rezgésidőn belüli skálákon szuperintenzív lézerterekben keltett legújabb nemlineáris ''attofizikai'' folyamatok elméleti és kísérleti vizsgálata. = Theoretical and experimental study of the newest nonlinear processes of ''attophysics'' generated by superintense laser fields within the light wavelength and oscillation period scale.

Számos fény-anyag kölcsönhatásra vonatkozó kísérleti vizsgálatot végeztünk el, femtoszekundumos, kevés ciklusú impulzusok által indukált fotoemisszió és felületi plazmonok által erősített elektrongyorsítás jelenségére vonatkozóan. Ezen kívül fejlesztéseket hajtottunk végre egy femtoszekundumos hosszú rezonátoros csörpölt impulzusú lézer oszcillátoron. Ez a fényforrás nagyon hasznos eszköz a fent említett kísérletekben. A elméleti kutatások során az attoszekundumos fizika, a nagy intenzitású fény-anyag kölcsönhatás és a kvantumoptika területén végezünk vizsgálatokat. A projekt során ezekből az elméleti és kísérleti témákból 19 referált nemzetközi folyóiratbeli publikáció jelent meg. | We investigated several light-matter interaction phenomena experimentally, including few-cycle pulse-induced photoemission and surface plasmon enhanced electron acceleration. We have carried out femtosecond laser development based on long-cavity, chirped-pulse laser oscillators. These sources provide very useful tools for the above mentioned experiments. In terms of theoretical studies, we investigated various field in attosecond physics, high-intensity light-matter interaction and quantum optics. These experimental and theoretical studies yielded 19 peer-reviewed journal publications during the duration of the project

Carrier-envelope phase controlled isolated attosecond pulses in the nm wavelength range, based on superradiant nonlinear Thomson-backscattering

A proposal for a novel source of isolated attosecond XUV -- soft X-ray pulses with a well controlled carrier-envelope phase difference (CEP) is presented in the framework of nonlinear Thomson-backscattering. Based on the analytic solution of the Newton-Lorentz equations, the motion of a relativistic electron is calculated explicitly, for head-on collision with an intense fs laser pulse. By using the received formulae, the collective spectrum and the corresponding temporal shape of the radiation emitted by a mono-energetic electron bunch can be easily computed. For certain suitable and realistic parameters, single-cycle isolated pulses of ca. 20 as length are predicted in the XUV -- soft X-ray spectral range, including the 2.33-4.37 nm water window. According to our analysis, the generated almost linearly polarized beam is extremely well collimated around the initial velocity of the electron bunch, with considerable intensity and with its CEP locked to that of the fs laser pulse.Comment: 11 pages, 6 figures, reviewed, corrected and extended work, regarding the intensity dependence of the emitted attosecond puls

Laser induced distortion of band structure in solids: an analytic model

We consider a spatially periodic (cosine) potential as a model for a crystalline solid that interacts with a harmonically oscillating external electric field. This problem is periodic both in space and time and can be solved analytically using the Kramers-Henneberger co-moving frame. By analyzing the stability of the closely related Mathieu-type differential equation, the electronic band structure can be obtained. We demonstrate that by changing the field intensity, the width of the zero-field band gaps can be drastically modified, including the special case when the external field causes the band gaps to disappearComment: 8 pages, 3 figure

Electron Acceleration by a Bichromatic Chirped Laser Pulse in Underdense Plasmas

A theoretical study of laser and plasma based electron acceleration is presented. An effective model has been used, in which the presence of an underdense plasma has been taken account via its index of refraction $n_{m}$. In the confines of this model, the basic phenomena can be studied by numerically solving the classical relativistic equations of motion. The key idea of this paper is the application of chirped, bichromatic laser fields. We investigated the advantages and disadvantages of mixing the second harmonic to the original $\lambda = 800 \, \mathrm{nm}$ wavelength pulse. We performed calculations both for plane wave and Gaussian pulses.Comment: 6 pages, 7 figures. Proceedings to the PIPAMON (2015) conference. Submitted to NIM-B Special Issue (SI:PIPAMON-2015). Accepted for publication: 7th of October, 201

Electron Acceleration in Underdense Plasmas Described with a Classical Effective Theory

An effective theory of laser--plasma based particle acceleration is presented. Here we treated the plasma as a continuous medium with an index of refraction $n_{m}$ in which a single electron propagates. Because of the simplicity of this model, we did not need to perform PIC simulations in order to study the properties of the electron acceleration. We studied the properties of the electron motion due to the Lorentz force and the relativistic equations of motion were numerically solved and analysed. We compared our results to PIC simulations and experimental data. Keywords: Underdense plasma; Electron acceleration; Classical electrodynamics; Relativistic equation of motion; Ultrashort laser pulsesComment: 14 pages, 7 figures. Proceedings to the ECLIM 2014 Conference (Paris). Submitted to Laser and Particle Beams (Cambridge Journals

Lézer-indukált ultragyors fémfelületi folyamatok vizsgálata. = Study of laser-induced ultrafast processes on metal surfaces.

A kutatási tervvel összhangban, a Max Planck Kvantumoptikai Intézettel való együttműködésnek köszönhetően felépítettünk Budapesten egy egyedi, 200 nJ-os, 40 fs-os impulzusokat adó Ti:zafír oszcillátort. A fény-anyag kölcsönhatások ultragyors dinamikájával kapcsolatos elméleti és kísérleti kísérleteket végeztünk mind Budapesten mind Németországban, különös tekintettel a felületi plazmonok által erősített elektrongyorsítás vizsgálatára. Ezeket az eredményeket részben már publikáltuk, a 2008-ban történt mérések eredményeinek publikálása pedig folyamatban van. | According to the research plan, based on the collaboration with the Max Planck Institute for Quantum Optics we built a unique Ti:sapphire oscillator delivering 200-nJ, 40-fs laser pulses. We also carried out studies related to the ultrafast dynamics of light-matter interactions both in Budapest and in Germany with particular focus on the investigation of the so-called surface plasmon enhanced electron acceleration. These results were partly published during the project and the publication of the 2008 measurement results is under way