12.5-GHz direct modulation bandwidth of vapor phase regrown 1.3-μm InGaAsP buried heterostructure lasers

A small-signal modulation bandwidth of 12.5 GHz is reported for vapor phase regrown 1.3-μm InGaAsP buried heterostructure (BH) lasers operated at a bias optical power of only 6.9 mW/facet. The bandwidth per square root of bias optical power is a factor of 1.6 higher than previous best results. In addition, the optical modulation amplitude remains flat to 12 GHz in sharp contrast to other types of BH lasers which exhibit signal roll-off at frequencies below the resonance frequency. The wide modulation bandwidth is attained by increasing the p-doping level in the active region and by the choice of short cavity length. The device is grown on a conductive substrate, indicating that it is unnecessary to use a semi-insulating substrate to obtain flat optical response in vapor phase regrown BH lasers.