Abstract. The principle of phase-locking of an axisymmetric fold combination cavity CO₂ laser, fulfilled by the reflection–injection of the back surface of the output-mirror, has been studied in detail. Variation of the equiphase surface and the influence of some characteristic parameters on phase-locking are analyzed—for example, phase error, changes in the cavity length and curvature radius, line-width and temperature. It is shown that the injected beam can excite a stable mode in the cavities, and the value of the energy coupling coefficient directly reflects the degree of phase-locking. Therefore, the output beams have a fixed phase relation between each other, and good coherent beams can be obtained by using the phase-locking method.

Keywords: ASFC CO₂ laser, phase-locking, energy coupling coefficient, coherent beams

Print publication: Issue 12 (December 2009)
Received 3 May 2009, accepted for publication 8 September 2009
Published 30 September 2009