Diode-pumped phosphate-glass laser has 88% slope efficiency

A diode-pumped 1.028 µm emitting room-temperature solid-state laser having a slope efficiency of 88% has been reported by researchers at the Universidad Autonóma de Madrid (Madrid, Spain) and the Universidad de São Paulo (São Carlos, Brazil). The gain medium is a ytterbium-doped QX phosphate glass developed by Kigre (Hilton Head, SC), and is end pumped with a 975 nm, 2 W laser diode couple to a 50 µm diameter optical fiber. The high slope efficiency leads to overall conversion efficiencies of greater than 50%.

The thickness of the gain region was reduced to 2 mm to make the confocal pump length longer than the gain region. The 2 × 5 × 3 mm, passively cooled, uncoated laser rod was formed in the shape of a parallelopiped. The distance between the input mirror and output coupler was 9.9 cm, creating a beam waist of 56 µm. The laser glass is athermal, has optical losses of below 1%, and a quantum defect as low as 4%. The maximum output power of the laser was 0.82 W in the TEM00 Gaussian mode. Contact Daniel Jaque at [email protected].