TWO-WAVELENGTH QUANTUM CASCADE LASERS WITH HETEROGENEOUS CASCADES

Dual-wavelength Quantum Cascade (QC) lasers with heterogeneous cascades are presented. In QC-lasers with interdigitated cascades the active core consists of a stack of active regions and injectors designed for emission at 8.0 um interleaved with a second stack emitting at 9.5 um. Clear laser action at two substantially different wavelengths is observed, demonstrating the viability of this approach to achieve multi-wavelength laser emission in the mid-infrared. Aside from providing two-wavelength operation, this laser design was also used to test the role of charge transport in the injectors, which customarily bridge successive active regions together. We present early results of the study on the transport properties and their impact on QC lasers. Furthermore, dual single mode emission at two substantially different wavelengths was demonstrated with a QC laser having two sub- stacks of lasers emitting at 5.0 um and 7.5 um. Both modes show clear single mode behavior and tunability equivalent to conventional single mode lasers in the mid infrared range.