Hot electron generation in a dense plasma by femtosecond laser pulses of subrelativistic intensity

We report a study of hot electron generation via the interaction of femtosecond laser pulses of subrelativistic intensity (10¹⁵ to 2×10¹⁷ W cm^-2), having different linear polarisations and nanosecond-scale contrasts, with the surface of "transparent" (quartz glass) and "absorbing" (silicon) targets. As the incident pulse intensity increases from 10¹⁵ to 10¹⁷ W cm^-2, the difference in hard X-ray yield and average hot electron energy between s- and p-polarised beams rapidly decreases. This effect can be understood in terms of relativistic electron acceleration mechanisms.