Obtención de pulsos de alta potencia en radiación laser por medio de un nuevo método en la conmutación de la cavidad de oscilación

Fil:Marconi, Mario Carlos. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina

Light collection and wavelength calibration for an extreme ultraviolet diode array spectrograph

Includes bibliographical references.We describe the use of a simple spherical aluminum-coated mirror to image the radiation of a distant XUV-emitting plasma in the slit of a vacuum spectrograph. Calculations to determine the optimum position and curvature radius of the mirror as a function of the divergence of the emitted plasma radiation are described, Efficient light collection by the grazing incidence mirror allows calibration of an intensified diode array used as a detector with a low-pressure (10-4 Torr) dc capillary discharge that does not require a complex differential pumping system.This work was supported by the National Science Foundation Grant No. ECS 8606226. M. C. Marconi was supported by a fellowship from Universidad Nacional de Buenos Aires and Consejo Nacional de Investigaciones Cientificas y Tecnicas de la Republica Argentina

Reliable passive mode locking with slow Q switching

An electro-optic modulator (EOM) has been added to a passive mode-locked Nd:glass laser in order to slow Q-switch the cavity. This guarantees that the laser will work near threshold even if the gain of the laser medium or the losses change from shot to shot. The losses at the EOM are used as the output coupling. This new configuration allows more reliable operation of the system

Study of the soft x-ray emission from carbon ions in a capillary discharge

Includes bibliographical references.The soft x-ray emission from plasma produced in polyacetal and polyethylene capillary discharges excited by current pulses 100 ns full-width half-maximum (FWHM), 50 ns risetime, and peak currents up to 60 kA has been studied. Time-resolved spectra show that intense Cᴠɪ line emission dominates in the polyethylene discharges, peaking shortly after the maximum of the current and vanishing before the end of the current pulse. Polyacetal capillary spectra are dominated by Oᴠɪ lines and show weak Cᴠɪ emission. Plasma density and temperature for the polyethylene discharge were derived from the Stark broadening of Cᴠɪ Balmer lines and the relative intensities of Cᴠɪ and Cᴠ lines. A short (5 ns FWHM) pulse of energetic beam electrons was detected in coincidence with the onset of the discharge. The results are discussed in relation to the possibility of obtaining soft x-ray amplification by plasma recombination in a capillary discharge plasma column.This work was supported by the Department of Energy, Advanced Energy Projects Grant DE-F602-91ER12110 and by the National Science Foundation by Grant ECS 9013372. The work of M. C. Marconi was supported by the Universidad Nacional de Buenos Aires and Consejo Nacional de Investigaciones Cientificas y Tecnicas de la Republica Argentina

Magnified expansion and compression of subpicosecond pulses from a frequency-doubled Nd:YLF laser

Includes bibliographical references.Pulses from a mode-locked frequency-doubled Nd:YLF laser have been spectrally broadened and subsequently expanded to more than 200 ps and recompressed to 750 fs by grating compressors with magnifying telescopes. The new design magnifies the time delay dispersion to a factor 10 times larger than achievable with standard compressors of similar size. The design of the system and its sensitivity to the variations in the position of its optical components is analyzed. The scheme will allow efficient amplification of subpicosecond pulses in dye amplifiers.This work was supported by N.S.F.-CONICET U.S.A./Argentina Cooperative Science Program under Grant INT 8802563, and by the National Science Foundation under Grants ECS 870507 and ECS 8606226. M. C. Marconi was supported by a Fellowship from the Universidad Nacional de Buenos Aires and Consejo Nacional de Investigaciones Cientificas y Tecnicas de la Republica Argentina

Electric field distribution in the cathode sheath of an electron beam glow discharge

We have measured the electric field distribution in the cathode sheath of an electron beam He glow discharge. Laser saturation spectroscopy was used to determine the quadratic Stark shift produced by the electric field. The experimental results are in good agreement with the calculations of a collisional model of the cathode sheath.This research was supported by the National Science Foundation under grant No. PHY-8508594 and the U.S. Air Force. JJR acknowledges the National Science Foundation for the support of a Presidential Young Investigator Award and an International Grant INT-8402914. MM was supported by a fellowship from the Universidad de Buenos Aires and Consejo Nacional de Investigaciones Cientificas y Tecnicas de la Republica Argentina

Nonconventional short-time dc magnetometer for superconducting films

Includes bibliographical references.A nonconventional technique for the measurement of magnetic relaxation in superconducting films at short times (~ 10-5 s) is described. This technique combines the application of a pulsed magnetic field and a synchronized high-energy pulsed laser. Remanent magnetic relaxation in (Y;Gd)Ba2Cu3O7-δ thin films is reported over five decades time at reduced temperatures above 0.8.This work was partially supported by Fundació Sauberán, EX018-UBA and EX285-UBA grants

Discharge-driven 46.9-nm amplifier with gain-length approaching saturation

Includes bibliographical references.Gain length products up to gl ≈ 14 for the J = 0-1 line of Ne-like Ar at 46.9 nm have been achieved in 15-cm long plasma columns generated by a fast capillary discharge. Amplification in plasma columns up to 20 cm in length was investigated. The laser line intensity is observed to increase exponentially for plasma lengths of up to 15 cm, above which it is observed to saturate. The saturation behavior is discussed.This work was supported in part by the National Science Foundation under grants ECS-9401952 and ECS-9412106, and the U.S. National Research Council

Effect of indirect Γ-L and Γ-X transfer on the carrier dynamics of InGaP/InAlP multiple quantum wells

Includes bibliographical references (page 104).Indirect Γ-L scattering within the well, and real space carrier transfer to the barrier X1c states are shown to significantly affect the carrier dynamics in In0.48Ga0.52P/In0.5Al0.5P multiple quantum wells. When carriers transfer to the indirect states occurs, the carrier dynamics is modified by the slow return of the carriers from the low mobility states to the well. As a result, the absorption recovery time increases by almost an order of magnitude. Carrier transfer to the indirect states also increases the carrier lifetime to values characteristic of indirect recombination.This work is supported by the National Science Foundation through Grant Nos. DMR 9321422, ECS-9502888, EEC-9015128, the Colorado Advanced Technology Institute, Grant No. 0594.75.0738, and by AFOSR contract F49620-93-1-0021

Application of extremely compact capillary discharge soft x-ray lasers to dense plasma diagnostics

Includes bibliographical references.Table-top capillary discharge soft x-ray lasers combine the advantages of a small size and a high repetition rate with an extremely high brightness similar to that of their laboratory-size predecessors. When utilized to probe high density plasmas their short wavelength results in a higher critical density, reduced refraction, decreased free-electron absorption, and higher resolution as compared to optical probes. These characteristics allow the design of experiments capable of measuring the evolution of plasmas with density-scale length products that are outside the reach of optical lasers. This paper reviews the use of a 46.9 nm wavelength Ne-like Ar capillary discharge table-top laser in dense plasma diagnostics, and reports soft x-ray laser interferometry results of spot-focus Nd:YAG laser plasmas created at moderate irradiation intensity (~7×1012 W cm-2) with ; ~13 ns pulse width duration laser pulses. The measurements produced electron density maps with densities up to 0.9×1021 cm-3 that show the development of a concave electron density profile that differ significantly from those of a classical expansion. This two-dimensional behavior, that was recently also observed in line-focus plasmas, is analyzed here for the case of spot-focus plasmas with the assistance of hydrodynamic model simulations. The results demonstrate the use of a table-top soft x-ray laser interferometer as a new high resolution tool for the study of high density plasma phenomena and the validation of hydrodynamic codes.This work was supported by the U.S. Department of Energy Grant No. DE-FG03-02NA00062 and by the National Science Foundation. Part of this work was performed under the auspices of the U.S. Department of Energy by the University of California, Lawrence Livermore National Laboratory through the Institute of Laser Science and Application, under Contract No. W-7405-Eng-48