High-power continuous-wave intracavity frequency-doubled Nd:GdVO4-LBO laser under diode pumping into the emitting level

The continuous-wave high power laser emission of Nd:GdVO4 at the fundamental wavelength of 1.06 mu m and its 531-nm second harmonic obtained by intracavity frequency doubling with an LBO nonlinear crystal is investigated under pumping by diode laser at 808 mn (on the I-4(9/2) -> F-4(5/2) transition) and 879 mn (on the I-4(9/2) -> F-4(3/2) transition). It is shown that, in spite of a lower absorption at 879 mn, the infrared emission is comparable under these two wavelengths of pump. The green emission performances were, however, improved by the 879 nm pump: 5.1 W at 531 nm with M-2 = 1.46 and 0.31 overall optical-to-optical efficiency was obtained from a 3-mm-thick 1-at. % Nd: GdVO4 laser medium and a 10-mm-long LBO nonlinear crystal in a Z-type cavity for 16.5 W pump power. In similar conditions, the maximum green power for the 808 nm pump was 4.4 W, with 0.26 overall optical-to-optical efficiency and M-2 = 3.40 beam quality; at this pump wavelength the green emission shows evident saturation for pump power in excess of 9.9 W. This behavior is connected with the enhanced heat generation under 809-nm pumping, as evidenced by the increased thermal lensing of the fundamental emission. A careful alignment of the laser enables emission almost free of chaotic intensity fluctuations.