Intense XUV pulses from a compact HHG setup using a single harmonic

We report on a compact and spectrally intense extreme-ultraviolet (XUV) source, which is based on high-harmonic generation (HHG) driven by 395 nm pulses. In order to minimize the XUV virtual source size and to maximize the XUV flux, HHG is performed several Rayleigh lengths away from the driving laser focal plane in a high-density gas jet. As a result, a high focused XUV intensity of 5 × 1013 W/cm2 is achieved, using a beamline with a length of only two meters and a modest driving laser pulse energy of 3 mJ. The high XUV intensity is demonstrated by performing a nonlinear ionization experiment in argon, using an XUV spectrum that is dominated by a single harmonic at 22 eV. Ion charge states up to Ar3+ are observed, which requires the absorption of at least four XUV photons. The high XUV intensity and the narrow bandwidth are ideally suited for a variety of applications including photoelectron spectroscopy, the coherent control of resonant transitions and the imaging of nanoscale structures.

Development of a high frequency ultrasonic setup for measuring the parameters of thin films

In this report a novel method for measuring the elastic properties of thin 10 nm films is described. The method is based on the use of a nanosecond laser for generation acoustic waves in solids. Absorption of the incident laser pulse energy and the associated temperature gradients induces a rapidly changing strain field. This strain field, in turn, radiates energy as elastic (ultrasonic) waves. At low pulse power, this is an entirely thermo elastic process resulting in no damage to the sample. The acoustic echo arriving at the probed surface causes both the displacement of the surface (a few nanometres) and the strain in the subsurface material, which might be detected through the variation of the optical reflectivity of the material, i.e. through the acousto-optic effect.

Surface characterization of laser-induced molten area in micro-grooving of silicon by ultraviolet (UV) laser

The objective of this research is to understand the fundamental mechanisms that govern the formation of laser-induced molten area during the micro-grooved fabrication on silicon material. In this research work, micro grooves were fabricated on silicon wafer by using ultraviolet (UV) laser of 248nm wavelength. Influence of lasing parameters such as pulse duration, laser pulse energy and scanning speed on the surface of micro-grooved was characterized. It is found that, the width of the micro grooves become wider with increasing laser pulse energy when ultraviolet laser was irradiated on silicon material. On the other hand, heat affected zone (HAZ) can be found at the surface of micro groove line at high pulse energy, high pulse repetition rate and lower scanning speed irradiation condition. This is considered due to the excessive heat input of the laser irradiation condition. It is concluded that proper selection of laser processing parameters of pulse energy, E, pulse repetition rate, R p , and scanning speed is necessary to achieve high quality micro-grooves.

The discharge initiation in vacuum gap by moderate intensity optical range radiation

The hypothesis of discharge initiation in vacuum gap by optical range radiation based on previously obtained experimental data. During the laser pulse interaction with electrode erosion products the glow discharge has ignited. In result of ioniza-tion-overheating instability the discharge has had current channel contraction and has transferred to arc. The dependences of material of target thermo dynamical parameters on the minimal and threshold laser pulse energy have demonstrated. The threshold laser pulse energy – the energy which enough to effective impact on the laser plasma.

INFLUENCE OF LASER ENERGY ON CDS NANO PARTIALS PREPARED BY LASER INDUCED PLASMA

In this work ,cadmium sulfide (CdS) thin films deposited on glass substrates using Nd-YAG laser wavelength (1064 nm) laser-induced plasma deposition technique (PLD). The structural, morphology and optical properties of these films have been described as a change in the effect of laser pulse energy ( ). The X-ray diffraction results show that s all samples were polycrystalline hexagonal structure and the crystalline size ghange with increasing of the laser energy. The optical properties results show that the transmittance of all deposited thin films decreases with increasing of laser pulse energy .As a result of the microscopic examination of the surface, it was found that the surface is uniform and the granular size increases with the increase of the laser power.

Relationship between wind observation accuracy and the ascending node of the sun-synchronous orbit for the Aeolus-type spaceborne Doppler wind lidar

The launch and operation of the first spaceborne Doppler wind lidar (DWL), Aeolus, is of great significance for observing the global wind field. Aeolus operates on a sun-synchronous dawn–dusk orbit to minimize the negative impact of solar background radiation (SBR) on wind observation accuracy. Future spaceborne DWLs may not operate on sun-synchronous dawn–dusk orbits due to their observational purposes. The impact of the local time of ascending node (LTAN) crossing of sun-synchronous orbits on the wind observation accuracy was studied in this paper by proposing two given Aeolus-type spaceborne DWLs operating on the sun-synchronous orbits with LTANs of 15:00 and 12:00 LT. On these two new orbits, the increments of the averaged SBR received by the new spaceborne DWLs range from 39 to 56 mW m−2 sr−1 nm−1 under cloud-free skies near the summer and winter solstices, which will lead to uncertainties of 0.19 and 0.27 m s−1 in the increment of the averaged Rayleigh channel wind observations for 15:00 and 12:00 LT orbits using the instrument parameters of Aeolus with 30 measurements per observation and 20 laser pulses per measurement. This demonstrates that Aeolus operating on the sun-synchronous dawn–dusk orbit is the optimal observation scenario, and the random error caused by the SBR will be larger on other sun-synchronous orbits. Increasing the laser pulse energy of the new spaceborne DWLs is used to lower the wind observation uncertainties, and a method to quantitatively design the laser pulse energy according to the specific accuracy requirements is proposed in this study based on the relationship between the signal-to-noise ratio and the uncertainty of the response function of the Rayleigh channel. The laser pulse energies of the two new spaceborne DWLs should be set to 70 mJ based on the statistical results obtained using the method. The other instrument parameters should be the same as those of Aeolus. Based on the proposed parameters, the accuracies of about 77.19 % and 74.71 % of the bins of the two new spaceborne DWLs would meet the accuracy requirements of the European Space Agency (ESA) for Aeolus. These values are very close to the 76.46 % accuracy of an Aeolus-type spaceborne DWL when it is free of the impact of the SBR. Moreover, the averaged uncertainties of the two new spaceborne DWLs are 2.62 and 2.69 m s−1, which perform better than that of Aeolus (2.77 m s−1).

Carbon Nanoparticles Synthesis By Different Nd:Yag Laser Pulse Energy

One of the most important techniques for preparing nanoparticle material is Pulsed Laser Ablation in Liquid technique (PLAL). Carbon nanoparticles were prepared using PLAL, and the carbon target was immersed in Ultrapure water (UPW) then irradiated with Q-switched Nd:YAG laser (1064 nm) and six ns pulse duration. In this process, an Nd:YAG laser beam was focused near the carbon surface. Nanoparticles synthesized using laser irradiation were studied by observing the effects of varying incident laser pulse intensities (250, 500, 750, 1000) mJ on the particle size (20.52, 36.97, 48.72, and 61.53) nm, respectively. In addition, nanoparticles were characterized by means of the Atomic Force Microscopy (AFM) test, pH easurement, and an Electrical Conductivity (EC) test of the nano solution. The smallest particle size was produced with (250) mJ laser pulse energy.

Пучки аномально ускоренных электронов, эмитируемые плазмой вакуумного разряда с лазерным поджигом

It is shown experimentally that a low-power pinch vacuum discharge with laser ignition can emit a beam of abnormally accelerated electrons with maximum energies per unit charge, almost an order of magnitude higher than the voltage across the discharge gap. It is established that the intensity of the X-ray radiation generated by the action of the beam on the target significantly decreases with increasing laser pulse energy. Maximum energy of X-ray quanta is inversely proportional to the mass of the cathode material ablated by laser radiation when the discharge is ignited. Possible mechanisms of the electron beam generation process are discussed.