Coaxial-geometry tunable dual-wavelength flashlamp-pumped Nd:Yag laser

Abstract

We propose to take advantage of the focalization effect of the pump light by the cylindrical laser rod in a side-pumped Nd:YAG laser (flashlamp or diode pumping) to obtain efficient two-wavelength operation. Under conveniently chosen conditions the focusing by the rod increases the pump power density in the near axial rod part about 2½ times, as we show, in comparison with the peripheral rod part. The focalization can strongly facilitate and to increase energetically the generation of weaker lasing lines in the axial part. This advantage is utilized by employing coaxial two-channel laser architecture, where the optically separated axial and peripheral parts of the rod generate each in its own spectral selective resonator. Beside the competition-less generation at two wavelengths (lines), other specific and essential advantages of the proposed laser solution are: (1) to produce emissions at a weaker line (generated in the axial part) and at a stronger line (in peripheral part), simultaneously and with equalized energy without loss of pump energy for the equalization; (2) the two emissions are produced and emitted naturally in coaxial beams using the full rod volume. We have realized such a laser with flash-lamp pumping (output to ~0.45 J; tunable pair of lines from 1.06, 1.32, 1.34, 1.36 and 1.44 μm) and carried out an experimental and theoretical study of its operation, including passive Q-switching.