Berlin 2015 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 94: Poster IV A (Laser; Devices; Heterostructures; Surfaces, interfaces and defects)
HL 94.4: Poster
Donnerstag, 19. März 2015, 14:00–20:00, Poster B
Selection of longitudinal modes in quantum cascade laser via narrow-band injection seeding — Hanond Nong1, Shovon Pal1,2, Sergej Markmann1, •Negar Hekmat1, Reshma A. Mohandas3, Paul Dean3, Lianhe Li3, Edmund H. Linfield3, Giles A. Davies3, Andreas D. Wieck2, and Nathan Jukam1 — 1Arbeitsgruppe THz Spektroskopie und Technologie, Ruhr-Universität Bochum, Germany — 2Lehrstuhl für Angewandte Festkörperphysik, Ruhr-Universität Bochum, Germany — 3School of Electronic and Electrical Engineering, University of Leeds, U.K.
Phase seeding is a technique to lock the phase of a quantum cascade laser (QCL) to the repetition rate of a fs laser, enabling access to the time-resolved THz-field of the QCL. In typical phase seeding all longitudinal modes in the gain region of a QCL are simultaneously seeded. We injection seed a THz QCL with narrow-band THz pulses which are generated in a periodically poled lithium niobate (PPLN) crystal. A THz seed pulse with a different frequency can be generated for each of the PPLN crystal’s multiple poling periods. The seed pulses’ FWHM are comparable to the longitudinal mode spacing of the QCL. When the longitudinal modes overlap the narrow-band seed spectrum they are selectively enhanced while other longitudinal modes are suppressed. When the narrow-band THz seed is shifted the QCL spectral emission also shifts to a higher longitudinal mode overlapping the seed. We study the dynamics of the QCL emission as a function of a round-trip time and a seed frequency. If the seed frequency is outside the gain maxima, a shifting to the preferential mode of a QCL is observed.