Passive and hybrid mode locking in multi-section terahertz quantum cascade lasers

Abstract

It is believed that passive mode locking is virtually impossible in quantum cascade lasers (QCLs) because of too fast carrier relaxation time. Here, we revisit this possibility and theoretically show that stable mode locking and pulse durations in the few cycle regime at terahertz (THz) frequencies are possible in suitably engineered bound-to-continuum QCLs. We achieve this by utilizing a multi-section cavity geometry with alternating gain and absorber sections. The critical ingredients are the very strong coupling of the absorber to both field and environment as well as a fast absorber carrier recovery dynamics. Under these conditions, even if the gain relaxation time is several times faster than the cavity round trip time, generation of few-cycle pulses is feasible. We investigate three different approaches for ultrashort pulse generation via THz quantum cascade lasers, namely passive, hybrid and colliding pulse mode locking.

References in corpus (7)

• Modeling techniques for quantum cascade lasers
• Short pulse generation and mode control of broadband terahertz quantum cascade lasers
• Monte-Carlo-based spectral gain analysis for THz quantum cascade lasers
• Active mode locking of quantum cascade lasers operating in external ring cavity
• Density matrix Monte Carlo modeling of quantum cascade lasers
• Self-induced transparency mode-locking, and area theorem
• Time-dependent transport in open systems based on quantum master equations

Cited by in corpus (5)

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• Optoelectronic device simulations based on macroscopic Maxwell-Bloch equations
• Mbsolve: An open-source solver tool for the Maxwell-Bloch equations
• Terahertz frequency combs exploiting an on-chip solution processed graphene-quantum cascade laser coupled-cavity architecture