Small-Signal Theory and Design of Traveling-Wave Semiconductor Cascade Lasers

Traveling-wave semiconductor cascade lasers (TWSCLs) are a form of series cascade laser (SCL) in which series-connected laser diodes are interconnected with commensurate transmission lines to create a periodically loaded structure. The inclusion of transmission line segments allows broadband impedance matching in addition to preserving the link gain improvements of conventional SCLs. This paper describes the small-signal analysis of TWSCLs using both transmission line theory and Bloch waves. The latter technique is then applied to a study of how transmission line and laser diode parameters affect both the return loss and gain-bandwidth product of TWSCLs.