6 GHz direct frequency modulation of cleaved-coupled-cavity channeled-substrate buried-heterostructure lasers

The measured intensity modulation (IM) and frequency modulation (FM) characteristics of single-cavity channeled-substrate buried-heterostructure (CSBH) lasers and cleaved-coupled-cavity (C
³
) CSBH lasers are described. If the bias is well above threshold, the lasers have -3 dB IM bandwidths of approximately 800 MHz. In contrast, the FM response rolls off less rapidly, and efficient FM operation up to 6 GHz is possible. The IM and FM responses of C
³
CSBH lasers are similar to single-cavity CSBH lasers provided the modulated cavity is above threshold. If the modulated cavity is below threshold, the FM response of the C
³
laser is larger but rolls off rapidly for modulation frequencies above 200 MHz.