Optically pumped cw molecular bismuth laser

Continuous laser oscillation of diatomic bismuth molecules was observed. The gaseous Bi2 was optically pumped on individual vibrational-rotational lines of the A–X band system by several single mode lines of a stabilized Ar+ laser. More than 150 Bi2 laser transitions are observed in the wavelength range between 590 and 790 nm and assigned to the A–X system. Laser power conversion efficiencies of up to 15% for broadband laser emission and up to 2.5% for single frequency laser emission were observed. Maximum Bi2 laser power was 150 and 25 mW, respectively. Low pump thresholds of the order of 40 mW are observed for single mode pumping of the strongest lasing transitions. Gain was determined from maximum output coupling to g≊0.02 cm−1. Using the optically pumped cw Bi2 laser as its own probe we measure the hyperfine structure of the Bi2(A–X) v′ = 17−v\ = 40 P(256) transition.