Random lasing in Nd3+ doped potassium gadolinium tungstate crystal powder

Random laser (RL) emission in Nd 3+ doped potassium gadolinium tungstate—KGd(WO4)2 :Nd 3+—crystal powder is demonstrated. The powder was excited at 813 nm in resonance with the Nd 3+ transition 4I9/2→4F5/2. RL emission at 1067 nm due to the 4F3/2→4I11/2 transition was observed and characterized. An intensity threshold dependent on the laser spot area and bandwidth narrowing from ≈2.20 nm to ≈0.40 nm were observed and measured. For a beam spot area of 0.4 mm2, a RL threshold of 6.5 mJ/mm2 (90 MW/cm2) was determined. For excitation intensity smaller than the RL threshold, only spontaneous emission from level 4F3/2 with decay time in the tens microsecond range was observed, but for excitation above the RL threshold, significant shortening of excited level lifetime, characteristic of a stimulated process was found. The overall characteristics measured show that KGd(WO4)2 :Nd 3+ is an efficient material for operation of solid state RLs in the near-infrared