Tuning properties of mid-infrared fabry-pérot quantum cascade lasers for multiheterodyne spectroscopy

Injection current tuning properties of an 8.5μm Fabry-Pérot mid-infrared quantum cascade laser are evaluated by analyzing the mode-by-mode frequency tuning behavior with an identification of high-noise regimes in a delayed self-heterodyne experiment. We find that modes on the edges of the spectral envelope exhibit anomalous tuning coefficients compared to those in the center. Furthermore, the frequencies of individual modes are susceptible to parasitic etalons, likely causing laser frequency pulling. Despite the complicated tuning behavior, low phase-noise operating regimes exist, and are compatible with high resolution multiheterodyne spectroscopy of gases.