Investigation of the ejected mass during high-intensity laser solid interaction for improved plasma mirror generation

The interaction of very intense and ultrashort laser pulses with solid targets is a topic that has attracted a large amount of interest in science and applications. This interest is boosted by the large progress made in the development of high repetition rate, high-power laser systems. With the significant increase in average power, there is concern about how to deal with ablated debris that may lead to contamination and damage during interaction experiments with solid targets. This issue is also highly relevant in experiments that include plasma mirrors. These are often employed to increase the contrast ratio of the intense laser pulse to unwanted laser pre-pulses from the amplifier chain and/or the background of amplified spontaneous emission. For this reason, the present work investigates the mass ejected from the target into vacuum for different conditions, particularly those present when plasma mirrors are introduced. The total amount of ablated mass can be reduced by making use of a temporally controlled plasma expansion that enhances the plasma mirror reflectivity. In this way, high intensity laser interaction experiments can be carried out with efficient and clean plasma mirrors significantly reducing the degradation of the laser optics and plasma diagnostics placed near the interaction.

Prediction of the irradiation doses from ultrashort laser-solid interactions using different temperature scalings at moderate laser intensities

The ionizing radiation created by high intensity and high repetition rate lasers can cause significant radiological hazard. Earlier defined electron temperature scalings are used for dose characterization and prediction using Monte Carlo modeling. Dosimetric implications of different electron temperature scalings are investigated and the resulting equivalent doses are compared. It was found that scaling defined by Beg et al.(1997) predicts the highest electron temperatures for given intensities, and subsequently the highest doses. The atomic number of the target, x-ray generation efficiency and interaction volume are the other parameters necessary for the dose evaluation. The set of these operational parameters should be sufficient to characterize radiological characteristics of ultrashort laser pulse based x-ray generators and evaluate radiological hazards of the laser processing facilities.

Effect of Flow Induced Parameters on the Output of A High Repetition Rate Dye Laser

The factors influencing the optical path stability in a dye laser flow cell are studied numerically and experimentally. A specially designed curved metallic dye flow cell providing a gain medium of 25 mm x 0.5 mm x 0.2 mm along with a compact resonator mechanical assembly is used in the study. The same configuration with gain medium of 15 mm x 0.5 mm x 0.2 mm is successfully used for single mode dye laser. The effects of flow induced vibrations on dye flow cell are studied with and without mechanically coupling it with the resonator structure for flow speeds varying from 1.33 m/s to 6.67 m/s at laser pump position. The effect of the mechanical instability, velocity fluctuation and temperature fluctuations in flowing dye solution on dye laser performance are studied at different flow speeds. These results are compared with the dye laser output parameters and found to be in good agreement. This study is useful in designing a high stability narrowband dye laser.