2 µm microchip laser based on Tm:YAG composite under 0.8 µm and 1.7 µm pumping

Composite Tm3+-doped Tm:Y3Al5O12, (Tm:YAG) microchip lasers were investigated. Effect of bonding the microchip rod with undoped YAG cap at one (YAG/Tm:YAG) and two (YAG/Tm:YAG/YAG) ends was studied and the results were compared to an unbonded Tm:YAG sample. The experiments were performed under 785 nm and 1700 nm diode pumping. The microchip rods had 3 mm diameter and 5/9/13 mm length. Faces were planar, polished and coated for HT at 1685 nm and 785 nm and HR at 1900–2050 nm at pumping end. Output coupler reflectivity value was R=98 The composite microchip lasers had advantageously high beam quality. At the maximum pumping power, the M2 parameter, measured by the knife-edge method, was M2=5.8 for the non-composite sample, which reduced to M2=4.5 for single-bonded and to M2=2.2 for double-bonded sample. There was a 30 End caps did not significantly influence output power or efficiency. The best obtained slope efficiency with respect to the absorbed power was 54.