Violet CW neodymium upconversion laser.

Abstract

Continuous-wave laser operation in the violet at 380 nm has been achieved on the 4D3/2 → 4I11/2 transition in LaF3:Nd3+ at temperatures of <90 K. Two different upconversion pumping mechanisms results in laser action: (a) sequential two-step absorption of an IR (790-nm) photon and a yellow (590-nm) photon by the Nd3+ ions; (b) cooperative energy transfer upconversion following the absorption of one yellow (578-nm) photon per Nd3+ ion. At temperatures near 20 K up to 12-mW power at 380 nm was obtained using pump powers of several hundred milliwatts from two CW dye lasers and conservative 1% output coupling. At 77 K, the output power decreased to approx. 4 mW.