TY - JOUR

T1 - Passive and hybrid mode locking in multi-section terahertz quantum cascade lasers

AU - Архипов, Ростислав Михайлович

AU - Tzenov, Petet

AU - Ihar, Babushkin

AU - Архипов, Михаил Викторович

AU - Rosanov, N.N.

AU - Morgner, U.

AU - Jirauschek, C.

N1 - Funding Information: This work was supported by the German Research Foundation (DFG) within the Heisenberg program (JI 115/4-2) and under DFG Grant No. JI 115/9-1 and the Technical University of Munich (TUM) in the framework of the Open Access Publishing Program. IB and UM are thankful for the financial support by DFG grants BA 4156/4-1 and MO 850-19/1. NR thanks Russian Foundation for Basic Research, project no. 16-02-00762a.

PY - 2018/5

Y1 - 2018/5

N2 - 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.

AB - 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.

KW - hybrid mode locking

KW - passive mode locking

KW - quantum cascade lasers

UR - http://www.scopus.com/inward/record.url?scp=85047970167&partnerID=8YFLogxK

U2 - 10.1088/1367-2630/aac12a

DO - 10.1088/1367-2630/aac12a

M3 - Article

VL - 20

JO - New Journal of Physics

JF - New Journal of Physics

SN - 1367-2630

IS - 5

M1 - 053055

ER -