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- ItemSubwavelength population density gratings in resonant medium created by few-cycle pulses(Bristol : IOP Publ., 2017) Arkhipov, R.M.; Arkhipov, M.V.; Pakhomov, A.V.; Babushkin, I.; Demircan, A.; Morgner, U.; Rosanov, N.N.We consider theoretically recently proposed a new possibility of creation, erasing and ultrafast control of population density grating. Such grating can be created in resonant medium when ultrashort pulses with duration smaller than relaxation times in the resonant medium (coherent light matter interactions) propagate without overlapping in this medium. Possible applications in the ultrafast optics such as optical switcher and laser beam deflector are discussed.
- ItemPassive and hybrid mode locking in multi-section terahertz quantum cascade lasers([Bad Honnef] : Dt. Physikalische Ges., 2018-05-24) Tzenov, P.; Babushkin, I.; Arkhipov, R.; Arkhipov, M.; Rosanov, N.; Morgner, U.; Jirauschek, C.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.