US Patent 7738518 Extended tuning in external cavity quantum cascade lasers

In a semiconductor lasers using quantum well gain medium, a quantum well stack is mounted in an epi-down configuration. The epitaxial side of the device may be directly bonded to an efficient heat transport system so that heat may more easily leave the quantum well stack layers and be disposed at a heatsink. Such a device runs cooler and exhibits reduced loss mechanisms as represented by a laser system loss-line. External cavity systems using this configuration may permit a high degree of tunability, and these systems are particularly improved as the tuning range is extended by lowered cavity losses.