Quantum cascade lasers enhance Mid-IR spectroscopy

QC lasers are based on the intersubband transitions between quantized subbands in multiple-quantum-well heterostructures. It is a design that is fundamentally different from that of conventional semiconductor lasers using interband transitions across a bandgap. Because QC lasers use intersubband optical transitions, they were once thought to be inefficient, and their emission spectra were thought to be inherently limited in tunability and breadth. However, research in recent years has shown that different quantum designs can be implemented to significantly improve the performance of these lasers. Many sensor applications require a sufficient wavelength-tuning range. Common techniques for tuning QC lasers include temperature adjustment, which yields a small tuning range, and mechanical tuning via an external cavity. QC lasers with broad gain spectra are ideal candidates for multianalyte mid-IR spectroscopy and sensor applications for broadband absorbers.