A method of phase locking two CO<sub>2</sub> lasers by radiation exchange is presented. This phase-locking was achieved by use of a copper prism as a beam folding device in the resonators and extraction of the output radiation by a common output coupler. Energy exchange led to a phase-locked state if several locking conditions were fulfilled. The amount of radiation injected from one resonator to the second cavity could be adjusted by movement of the prism. The influence of the strength of coupling on the locking range was studied. The beat signal between the two unlocked lasers could be measured, whereas in the case of phase-locked operation twice the intensity was detected. Despite the inclusion of several assumptions, a simplified mathematical model delivered good agreement between calculated and experimental results.
© 2001 Optical Society of America
(140.3390) Lasers and laser optics : Laser materials processing
(140.3410) Lasers and laser optics : Laser resonators
(140.3470) Lasers and laser optics : Lasers, carbon dioxide
(140.3520) Lasers and laser optics : Lasers, injection-locked
Wendelin Weingartner, Kurt Schröder, and Dieter Schuöcker, "Phase Locking of CO2 Lasers," Appl. Opt. 40, 2453-2460 (2001)