Single-longitudinal-mode stabilized graded-index-rod external coupled-cavity laser

Abstract
An active-passive coupled-cavity semiconductor laser using a slightly shorter than 1/4 pitch graded-index-rod lens reflector as the external cavity has been demonstrated. The graded-index lens is prepared from an optical fiber waveguide. We report (1) stable single-longitudinal-mode operation of the graded-index-rod external coupled-cavity (GRECC) lasers with 2-Gbits/s modulation and (2) digital transmission at 1 Gbits/s over 99 km of fiber using a 1.55-μm GRECC laser.