Abstract

Generation of intense, ultrashort optical pulses with a high contrast between the main pulse energy and prepulse energy is essential to creating hot solid-density plasmas that emit ultrafast x-ray pulses.¹ Prepulse energy focused to intensities above 10¹² W/cm² may cause ionization before the femtosecond pulse arrives at the target surface. Significant hydrodynamic expansion of preionized plasma changes the nature of the femtosecond pulse interaction to a laser-plasma coupling with cooler, low-density plasma.

© 1995 Optical Society of America