Abstract

Sun-pumped lasers are useful for space and terrestrial applications. In terms of collection efficiency and beam quality, solar lasers still have a way to go to seriously compete with solar PV-cell diode-pumped solid-state lasers. The main challenges are the needs of both doubling the reported collection efficiency¹ of 6.7W/m² and improving the beam quality of today’s solar lasers. To enhance the solar laser performance, a truncated fused silica elliptical pump cavity is proposed. With the first-stage parabolic mirror of 1,5m diameter, the solar power is both collected and concentrated into the 8mm diameter focal spot of 1250W. The input face of the truncated cavity is then mechanically positioned at the focal area of the parabolic mirror (Fig. la). On passing through the air-fused silica interface, the concentrated rays of 60° rim-angle are refracted into the divergent rays of 36° rim-angle within the cavity machined from fused silica material. By both the reflections from a gold cavity reflector and the total internal reflections from the side faces of the cavity, the concentrated solar radiation is efficiently transferred from the first focal line, coplanar with the input face of the cavity, to the second focal line, where a laser rod is mounted and actively cooled by water. For the 1.0% Nd: YAG rod of 4mm diameter and 30mm length, a nearly symmetric absorbed flux profile is obtained (Fig.l b, Fig.l c). The absorbed flux peaks along the central core region of the rod, favouring the generation of TEM₀o laser power.

© 2007 IEEE