Thermally boosted pumping of neodymium lasers.

Pumping at 885 nm from thermally excited ground-state levels directly to the Nd:YAG upper lasing level is experimentally demonstrated by use of a Ti:sapphire pump laser. This approach utilizes thermal energy contained within the laser medium to provide part of the pump energy required to achieve population inversion. Slope efficiency increased by 12% compared with traditional pump band excitation (lambda(pump) = 808 nm) and by 7% compared with ground-state direct pumping (lambda(pump) = 869 nm). The combined transition from the first and second thermally excited Stark components of the ground state (4I(9/2)) to the upper lasing level (4F(3/2)) has characteristics that make thermally boosted pumping a suitable candidate for use with diode lasers: reasonable absorption (1.8 cm(-1)) and bandwidth (2.7 nm FWHM). A model suggests that, compared with traditional 808-nm pumping, heat could be reduced by 40% by use of thermally boosted pumping.