Spectroscopy and diode laser-pumped operation of Tm,Ho:YAG

Spectroscopic measurements and analysis of diode laser-pumped operation of Tm,Ho:YAG at 2.1 mu m at room temperature have been performed. The peak effective stimulated emission cross section is measured to be 9*10/sup -21/ cm/sup 2/ at 2.091 mu m and the upper state lifetime is 8.5 ms. Under diode laser pumping, thresholds of 4.4 mW of absorbed power and slope efficiency of 19% have been demonstrated. Calculations of threshold power are performed based on the spectroscopic measurements. An energy transfer upconversion process is identified which leads to a sublinear rise in upper-state population with pump power.<
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