High-speed optically controlled semiconductor light source with an external cavity

An optically controlled semiconductor laser with broad 3-dB bandwidth is achieved by introducing a phase- and intensity-controllable external cavity into a DFB laser. The external cavity functions as a passive-feedback section for the semiconductor laser. The optimum structure of an optically controlled passive-feedback laser (OC-PFL) for widening the 3-dB bandwidth of the laser is numerically analyzed. A broad 3-dB bandwidth of up to 40 GHz is experimentally confirmed by using a fabricated OC-PFL with a structure designed on the basis of the analysis results. It is also experimentally confirmed that it is possible to achieve 3-dB bandwidth of more than 50 GHz.