Chaotic Behavior of Quantum Cascade Lasers at Ignition

The ignition of Quantum Cascade Lasers can occur from a state of oscillating fie ld domains. Here, the interplay between lasing and the kinetics of traveling dom ain boundaries provides complex oscillation scenarios. We analyze our numerical findings in detail for a device operating at terahertz frequencies and manifest chaotic evolution by positive Lyapunov exponents. This shows that these importan t devices can exhibit chaotic behavior even without periodic driving, which need s to be taken into account in their design.