Thermal and Stark-Effect Roll-Over of Quantum-Cascade Lasers

A computational and experimental analysis of rollover in high-performance lambda ~ 8 mum quantum-cascade (QC) lasers is presented. In addition to conventional, thermal rollover, which is also a common cause of power rollover in diode lasers, ";Stark-effect"; rollover is observed. While both effects can occur in the same QC laser design, thermal and Stark-effect rollover are shown to be the dominating factor for high-temperature continuous wave operated, and pulsed low-temperature operated and low-doped lasers, respectively. Additionally, the role of the continuum above the wells and barriers is discussed for both effects.