Highly efficient Nd:LGSB laser under direct pumping

• The first continuous wave directly pumped Nd:LGSB laser is reported. • Slope efficiencies close to quantum defect level are attained with direct pumping. • Comparison of laser performances for indirect versus direct pumping is performed. • Heating of continuous wave directly pumped Nd:LGSB crystal is analyzed. • Nd:LGSB infrared laser power upscaling is discussed. A directly pumped Nd:LGSB laser around 1.06 μm is explored for the first time, to our knowledge. A maximum continuous wave output power of 3.05 W is measured at 4.22 W absorbed pump power for a Nd:LGSB c -cut medium pumped directly into 4 F 3/2 emitting level, placed in a plane-plane cavity. The laser was operated with high −0.80- slope efficiency, close to 0.83 quantum defect level. By comparing the laser performances for continuous wave diode pumping at 880 nm with conventional 807 nm, while keeping similar laser cavity conditions, increases of 15 % of slope and 14 % of optical-to-optical efficiencies were observed, at optimum 5 % transmission of the output coupler. In addition, temperature measurements during continuous wave direct pumping of Nd:LGSB crystal are presented, envisaging further laser power scaling. The enhanced infrared lasing performance offers motivation for future studies aiming boosted visible emission of Nd:LGSB bifunctional crystal under direct pumping condition.