Cs. Tóth

Proposal for attosecond light pulse generation using laser induced multiple-harmonic conversion processes in rare gases

Abstract A new principle of attosecond light pulse generation is suggested. The method is based on a Fourier synthesis of laser induced multiple harmonics, which all are oscillating with the same fixed phase as predicted and observed recently in rare gases. According to our calculation using published experimental data, the production of a regular sequence of ∼30–70 as duration light pulses is expected to be realizable.

High current, small divergence electron beams produced by laser‐induced surface photoelectric effect

The potential application of the laser induced linear surface photoelectric effect for high current and small divergence electron beam formation is examined. The temporal evolution of the current pulses and the angular distribution of the photoelectrons produced following KrF laser irradiation of a gold surface is studied as a function of laser intensity. A threshold laser intensity of (140±20) MW/cm2 was determined, below which the single photon photoeffect dominates any laser induced thermionic emission process. Electron current measurements for vertical and horizontal polarization of the incident laser radiation showed that the current contribution from the surface photoeffect is about three times larger than that from the volume photoeffect. Under these conditions, an angular distribution of the produced electrons of 17°±2° was determined. The estimated normalized transverse beam emittance is 20π mm mrad.

Laser-induced electron emission from an Au surface irradiated by single picosecond pulses at λ=2.94 μm. The intermediate region between multiphoton and tunneling effects

The photoinduced electron emission from the surface of a solid gold target irradiated by single picosecond pulses of an erbium laser is investigated. The applied laser intensity (5–120 GW/cm2) corresponds to the intermediate interaction region between the pure multiphoton and tunnel effects, where the decisive Keldysh-parameter, γ, is in the range 1<γ<12=n0. In the light intensity region which is free of surface heating (IL<80 GW/cm2), the slope of the measured logarithmic intensity dependence of the photocurrent decreases from the n0=12 perturbative value down to n ℞ 5. Therefore the experiment shows that the Keldysh-type theories, which have recently been proved to describe correctly the ionization of atoms, are also valid to a certain extent in the case of the photoeffect in metals.

Linear surface photoelectric effect of gold in intense laser field as a possible high‐current electron source

Investigations were conducted on radiation‐induced electron emission processes on a gold target surface with a high‐intensity (2 MW/cm2) KrF laser (λ=248 nm). The single photon surface photoelectric emission obtained can be used for high‐current density electron sources. The measured polarization dependence of electron current shows the dominance of the surface‐type effect over that of the volume type, thereby making it possible to optimize the short, high‐density electron current creation conditions. The advantage of the grazing light incidence and the multiphoton photoeffect giving rise to a 500 A/cm2 electron current has been demonstrated.

Enhancement of ultraviolet laser plasma emission produced in a strong static electric field

Abstract Enhancement of the ultraviolet (UV) radiation (200–350 nm) emitted from a laser produced plasma created on a gold target surface in the pressure of high negative static electric field by an order of magnitude was observed. Electric field induced recombination processes are posited as a mechanism for the UV radiation enhancement.

GENERATION AND TUNING OF SECOND HARMONIC RADIATION PRODUCED BY ULTRASHORT DYE LASER PULSES FROM A GOLD SURFACE

Tunable second harmonic radiation has been generated on a gold surface by means of a dye laser system capable of emitting pulses of 450 fs and 4.5 ps duration. The intensity of harmonic radiation was maximum along the direction of the reflected incident laser beam, when the polarization direction of the incoming radiation was vertical to the target surface (p polarization). The efficiency for second harmonic generation was found to depend strongly on the pulse duration of the laser beam. The observed change of the harmonic generation efficiency as a function of the angle of incidence and the pulse duration of the laser beam suggests that, due to coherence effects, the actual overlapping spatial dimension of the interaction region between the laser pulse and the electron gas of the metallic surface plays an important role.

Wavelength dependence of harmonic generation efficiency at metal surfaces induced by femtosecond Ti:sapphire laser pulses

Abstract Second and third order harmonics of high intensity (∼ 10 10 W/cm 2 ), femtosecond Ti:sapphire laser pulses were generated at a gold surface. The spectral dependence of the second harmonic generation efficiency was measured as a function of the fundamental excitation wavelengths (780–850 nm). The efficiency is found to decrease significantly toward the longer wavelengths. This behavior is consistent with the recently observed very low efficiency of the high order harmonic generation at infrared wavelengths (1–3 μm), while contradicting the single particle perturbative theoretical descriptions of the harmonic generation process at the vacuum/metal interface.

Enhancement Of The X-Ray Emission Of Laser Induced Plasma In The Presence Of A High Static Electric Field

The influence of a static electric field on the X-ray plasma emission induced by a picosecond NdYag laser on a Au target has been investigated. The X-ray emisson of the plasma, created by focusing the laser beam down to an intensity of 1014 W/cm2, lies in the region of 1-20keV and was studied as a function of the applied static electric field. A significant increase of the intensity of the X-ray emission is observed at high electric fields (20kV/cm).

Laser induced electron emission from gold surface irradiated by picosecond pulses at λ=2.9 μm

A nonlinear photoelectric emission from a gold surface irradiated by intense (16 GW/cm2) ultrashort (≈100 ps) erbium laser pulses of the 3-micron wavelength region was observed. The results obtained were interpreted by the theoretically predicted thermally enhanced multiphoton photoemission.

Pulsed laser field errors: theoretical and experimental analysis of a phase error figure of merit

Summary form only given. Several pulse distortion analysis methods have been recently used to quantify pulse errors. We have used PGFROG to retrieve the spectral phase and intensity for a variety of distorted pulses. The measurements were done in a single shot mode to allow the analysis of pulse-to-pulse statistics.