Fast switching between continuous-wave and passively mode-locked regimes of Nd:YVO4 and Cr:LiSAF lasers

We present the use of an optically-pumped saturable absorber (SA) inside Nd:YVO₄ and Cr:LiSAF lasers as a viable method to remotely control the laser mode of operation. CW operation in both lasers was obtained by cooling the SAs down to -10degC with a thermo-electric cooler. Two types of the SAs were used: the first one, originally designed as the active region of a semiconductor disk laser, was employed in picosecond Nd:YVO₄ laser, while the second one, a semiconductor Bragg reflector, was used in femtosecond Cr:LiSAF laser. The external pump power necessary to promote a given operational state in the case of Nd:YVO₄ laser was dependent on the laser pump power but in the case of Cr:LiSAF laser, the regime of operation itself was not dependent upon the external pump power. Finite element thermal analysis of the SA in the Nd:YVO₄ laser has been performed in order to evaluate the average temperature changes induced by external pumping, and to compare these figures with those experimentally obtained by heating the device with the TEC. Stable CW and CW ML operation of the lasers occurred when the SA mount temperature was set to -10 and +1degC.