Nd:YAG laser pumped at 946 nm

Abstract

A Nd:YAG laser crystal was pumped at 946 nm and lased at 1064 nm. This pump-lase format was investigated in order to reduce the quantum defect between the pump and laser photons as compared to other pump schemes of this material. To the best of our knowledge, this is the first realization of this scheme. A room temperature absorption coefficient and linewidth of approximately 0.075 cm(-1) and approximately 1 nm for 1% at. Nd(+3) concentrations were measured for the 946 nm absorption line. Those parameters impose both narrow-bandwidth pumping and a long absorption path. By increasing the laser crystal temperature above room temperature, the absorption cross sections at 946 and 938 nm increase due to enhanced thermal population of the upper energy level of the ground manifold. The possibility of exploiting this phenomenon to enhance the pump absorption is also discussed.

Nd:YAG laser diode-pumped directly into the emitting level at 938 nm

“…We calculated the overlap to be 39 % at room temperature taking into account the measured width of our laser diode (2.5 nm) and the absorption linewidth temperature dependence given by Goldring & al. [10]. The calculated values for the absorption matched perfectly the experimental data (see on Fig.…”

“…This corresponds to a slope efficiency of 28 %. Even if it is the first demonstration of a Nd:YAG diode-pumped at 938 nm, this efficiency remains lower than the one obtained under Ti:Sapphire pumping at 946 nm (42 %) [10] and much lower than expected by the quantum defect (88%). The last part of our work is devoted to the analysis of this low efficiency and to present several ways of improvements.…”

“…At room temperature, the pump absorption was so low (only 19 %) that even at 120 W of pump power, the temperature increase induced by the pumping was not detectable. Fortunately, Goldring et al [10] showed that the absorption can be improved by a global temperature increase, as the upper level of the ground state manifold is more populated. In our case, the crystal rod was heated up to a temperature of 150°C which was the upper limit before the degradation of the thermal grease around the rod.…”

“…Hence this leads to a quantum defect of 12% (and 11 % respectively) which is very close to the Yb:YAG one. A first demonstration has been recently reported [10] with a Ti:Sapphire laser as a pump source at 946 nm. As the absorption peaks are very low and narrow (1nm full width at half maximum) at 946 nm and at 938 nm, the diffraction limited beam and the narrow spectral linewidth of the Ti:Sapphire laser were very useful: an output power of 60 mW was obtained for a double pass pumping at 946 nm in a 6 cm long 1.1 at.% doped Nd:YAG crystal.…”

Crystal growth, spectral and laser properties of Nd:LuAG single crystal

“…Nd-doped crystals, such as Nd:YAG, Nd:YVO 4 , Nd:GdVO 4 , and Nd:LuVO 4 have recently attracted much attention due to their possible utilization as efficient diode pumped solid state lasers [5][6][7][8][9][10].…”