Abstract

Reflective optical feedback from an external cavity has been widely used for narrowing the linewidth of semiconductor lasers. Compact narrow-linewidth lasers using fiber waveguides^1,2 or a graded-index rod³ as the external cavity have been demonstrated. In these lasers, the linewidth is narrowed by a weak optical feedback from the external reflector. We report a fiber-extended-cavity distributed-feedback (DFB) laser which differs from previous devices in that it employs strong coupling between an antireflection (AR)-coated DFB laser and an optimized external fiber cavity. The laser exhibits stable narrow-linewidth operation and is insensitive to spurious external reflections.

© 1986 Optical Society of America