Diode-pumped cw lasing of Yb, Ho : KYF4 in the 3 μm spectral range in comparison to Er : KYF4

We present diode-pumped cw lasing at room temperature of Yb3+-COdOpCd Ho : KYF4 on the transition 5I6 → 5I7 in bulk material. Laser experiments with Ti : Al2O3 and diode excitation at 970 nm were performed. The pump energy is absorbed by Yb3+ and then transferred to the upper laser level 5I6 in Ho3+. In a second step, the lower laser level 5I7 is depopulated by an upconversion process (2F5/2, 5I7) → (2F7/2, 5F5) and by excited-state absorption (ESA) at the pump wavelength. The observed laser wavelength was 2.84 μm. Under Ti : Al2O3-pumping, a slope efficiency of 1% with respect to incident power and a maximum output power of 11 mW could be achieved. With laser diodes as pump sources the slope efficiency was reduced to 0.3% with a maximum output power of 2.5 mW. These diode-pumped laser results are compared with the 3 μm laser in Er : KYF4 under the same experimental conditions. In addition, spectroscopical data are presented for both systems. Copyright © 1998 by MANK Hayka/Interperiodica Publishing