Coherent combination of four laser beams in a multi-axis Fourier cavity using a diffractive optical element

Abstract : Thermal aberrations in diode-pumped solid-state laser media are well known. To avoid these effects we propose to end-pump separated zones of a laser crystal with elementary beams of moderate power. We present a multi-axis laser cavity with a single-gain medium longitudinally pumped by four fibre-coupled laser diodes. The four elementary laser beams are coherently combined inside the cavity by a diffractive optical element. 82% of the laser power is focused in a single diffraction limited beam.