Abstract
Coherent-cavity combining (C3) is a power addition technique that can maintain high beam quality using
coupled laser cavities. The number of laser modules that can coherently be combined in coupled cavities
is limited by the mismatch of individual longitudinal modes. Our present work increases the number of
coupled lasers by precise control of cavity lengths. In this paper, we report a novel C3 fiber laser with an
optical-path-length control technique that uses an aluminum coated fiber (ACF) to which electric power
is applied. The technique with an ACF completely consists of the longitudinal modes of two individual
fiber lasers in the coupled cavity. The C3 system with ten laser modules achieved a combined efficiency
of 90.2% when the technique with an ACF completely consisted of individual longitudinal modes of two
out of ten laser modules.
