Dollar, F. and Cummings, P. and Chvykov, V. and Willingale, L. and Vargas, M. and Yanovsky, V. and Zulick, C. and Maksimchuk, A. and Thomas, A. G. R. and Krushelnick, K. (2013) Scaling High-Order Harmonic Generation from Laser-Solid Interactions to Ultrahigh Intensity. Physical review letters, 110 (17): 175002. ISSN 0031-9007
Full text not available from this repository.Abstract
Coherent x-ray beams with a subfemtosecond (<10(-15) s) pulse duration will enable measurements of fundamental atomic processes in a completely new regime. High-order harmonic generation (HOHG) using short pulse (<100 fs) infrared lasers focused to intensities surpassing 10(18) W cm(-2) onto a solid density plasma is a promising means of generating such short pulses. Critical to the relativistic oscillating mirror mechanism is the steepness of the plasma density gradient at the reflection point, characterized by a scale length, which can strongly influence the harmonic generation mechanism. It is shown that for intensities in excess of 10(21) W cm(-2) an optimum density ramp scale length exists that balances an increase in efficiency with a growth of parametric plasma wave instabilities. We show that for these higher intensities the optimal scale length is c/omega(0), for which a variety of HOHG properties are optimized, including total conversion efficiency, HOHG divergence, and their power law scaling. Particle-in-cell simulations show striking evidence of the HOHG loss mechanism through parametric instabilities and relativistic self-phase modulation, which affect the produced spectra and conversion efficiency. DOI: 10.1103/PhysRevLett.110.175002