Abstract

Advances in the field of high power solid state lasers have in recent years concentrated on maximising the energy extraction efficiency in an effort to control the costs of proposed new facilities, such as the US National Ignition Facility (NIF) and the French Laser Megajoules (LMJ). In essence, this has involved the application of multi-passing of large aperture Neodymium-doped glass (Nd:glass) amplifiers at all stages of the laser. The technology of multi-passing also has attractions for existing facilities as it potentially allows for a reduction in operational costs while maintaining current system performance. The HELEN three-beam 2TW Nd:glass laser has operated in single-pass configuration for the past 20 years for the purpose of investigating the physics of laser-generated plasmas. Similar cost-reduction pressures have recently provided a motivation for a far-reaching redesign of the HELEN laser using multi-pass principles, as shown in Fig 1. A single, diode-pumped Q-switched Neodymium-doped Yttrium Lithium Fluoride (Nd:YLF) ring oscillator provides a stable single longitudinal mode pulse of 1053nm wavelength.

© 2000 IEEE