Broadband tuning in optical communication band using Fabry-Perot laser diodes without antireflection coating

A broadly tunable range of 200 nm is achieved in external cavity semiconductor laser using a Fabry-Perot laser diode as an amplifier. The broadband tuning is possible due to two reasons. First, the gain bandwidth is broadened using proper design of nonidentical quantum-well structure. Second, carriers distribute over a broad bandwidth, leading to the reduction of gain over a narrow bandwidth. Thus self-oscillation of uncoated Fabry-Perot laser didoes is suppressed, but there is still gain for external-cavity configuration. A tuning range covering from 1340nm to 1540nm is then achieved.