Chaotic Light at Mid-Infrared Wavelength
Résumé
The onset of nonlinear dynamics and chaos is evidenced in a mid-infrared distributed
feedback quantum cascade laser both in the temporal and frequency domains. As opposed to the
commonly observed route to chaos in semiconductor lasers, which involves undamping of the
laser relaxation oscillations, quantum cascade lasers first exhibit regular self-pulsation at the
external cavity frequency before entering into a chaotic low-frequency fluctuation regime. The
bifurcation sequence, similar to that already observed in class A gas lasers under optical
feedback, results from the fast carrier relaxation dynamics occurring in quantum cascade lasers,
as confirmed by numerical simulations. Such chaotic behavior can impact various practical
applications including spectroscopy, which requires stable single-mode operation. It also allows
the development of novel mid-infrared high-power chaotic light sources, thus enabling secure
free-space high bit-rate optical communications based on chaos synchronization.