Although organic solid-state dye lasers have the potential for numerous applications, to date they have only been pumped with pulsed light sources. Continuous-wave (CW) operation has not been possible because of long-lived transient absorption that gradually builds up, reducing the gain and terminating the lasing process. But thanks to a high-quality thin-film laser medium sandwiched between two clear digital video disks (DVDs; chosen for mechanical and optical-design reasons), researchers at Universität Karlsruhe (Karlsruhe, Germany) and Universität Siegen (Siegen, Germany) have demonstrated CW lasing of more than 20 mW over a tuning range of more than 40 nm.
The gain medium is a 50- to 100-µm-thick layer of rhodamine 6G dye incorporated in a stable polymer host with a specific concentration at the pump wavelength of 532 nm. Sandwiched between the DVDs, the solid dye-laser disk has an overall thickness of approximately 1.2 mm and a diameter of 120 mm. By rotating the laser disk with a frequency of 50 to 100 Hz and translating it perpendicular to the rotational axis with a velocity of 100 to 300 µm/s, the accumulation of long-lived excited states in the gain volume is eliminated and CW lasing is possible. Contact Uli Lemmer at [email protected].