Theoretical and numerical analysis of superluminescent diodes

The authors present a set of simple analytical expressions for the design of superluminescent diodes (SLDs). To validate the analytical model, numerical simulations by a comprehensive mixed frequency-domain-time-domain traveling-wave model are performed. Through a comparison between them, guidelines for design optimization of SLDs are also discussed. In particular, the authors focus on the effects of the design parameters (e.g., cavity length and active region cross-sectional area) and operating condition (i.e., bias current) on the performance of SLDs (e.g., output power spectrum and power-bandwidth product). The good agreement between the analytical and numerical results demonstrates that the power-bandwidth product of SLDs can be enhanced by increasing the cavity length, reducing the active region cross-sectional area, and raising the operating current. It is shown that the dilution of carrier density along with the modal loss is the main factor that limits the cavity length.