Diode-pumped master oscillator power amplifier system based on cryogenically cooled Tm:Y2O3 transparent ceramics

We demonstrated a master oscillator power amplifier system using cryogenically cooled Tm:Y2O3 transparent ceramics. The electro-optically switched master oscillator acted as a seed source and could be tuned from 1 to 100 Hz. A maximum pulse energy of 1.35 mJ with a pulse duration of 30 ns amounting to a peak power of 45 kW was obtained at 10 Hz. The power amplification via double-pass geometry achieved maximum single pulse energy of 2.94 mJ at 10 Hz with a pulse duration of 32 ns. The results showed the pulsed lasing potential of Tm:Y2O3 transparent ceramics at cryogenic temperatures. This gain material can be considered as an alternative gain medium for high average and peak power laser development around 2 mu m in nano-second regime. Pulsed lasers generating high energy/power in the 1.8-2.0 mu m region based on the 3F4 -, 3H6 transition of Tm3+ (hereafter: Tm) possess broad applications in several fields such as laser induced damage threshold (LIDT) measurement, polymer material processing, remote sensing, medical surgery, pump source for mid-infrared lasers, etc. [1-5]. The advantages of such lasers are mainly due to two reasons: 1) the 3H6 -, 3H4 transition and 2) the cross-relaxation process. The former can be easily excited by the commercial AlGaAs laser diodes emitting around 800 nm, and the latter increases the laser efficiency by gathering two excited Tm ions for each absorbed pump photon on the 3F4 laser level [6]. However, at room temperature, due to the quasi-three-level nature of Tm ion, the material suffers from reabsorption losses due to the finite population in the 3H6 laser level. This in turn results in higher laser threshold and limits the