Abstract-Laser-seeding dynamics with few-cycle pulses: Maxwell-Bloch finite-difference time-domain simulations of terahertz quantum cascade lasers

Joshua R. Freeman, Jean Maysonnave, Suraj Khanna, Edmund Linfield, A. Giles Davies, Sukhdeep S. Dhillon, and Jérôme Tignon

http://pra.aps.org/accepted/c107eNceP701751e604f1373d9f2f77c5fdeba29b

We implement a Maxwell-Bloch simulation for a two-level system within the FDTD method to simulate the seeding of lasers by broadband pulse injection. The model does not make the slowly varying envelope approximation and the full electromagnetic field is simulated so that we are able to obtain time resolved seeding by few-cycle pulses. The model is compared to recent results on seeding of THz quantum cascade lasers to aid interpretation of their complex signals. The simulations are found to be in good agreement with the data when gain recovery times of 15ps are used. Furthermore we find that the emission from the laser depends only weakly on the seed used to initiate laser action. The model is readily applicable to any seeded laser system where few-cycle seed pulses are used.

Abstract-Direct intensity sampling of a modelocked terahertz quantum cascade laser

http://apl.aip.org/resource/1/applab/v101/i18/p181115_s1?bypassSSO=1

Joshua R. Freeman¹, Jean Maysonnave¹, Nathan Jukam², Pierrick Cavalié¹, Kenneth Maussang¹, Harvey E. Beere³, David A. Ritchie³, Juliette Mangeney¹, Sukhdeep S. Dhillon¹, and Jérôme Tignon¹

¹Laboratoire Pierre Aigrain, Ecole Normale Supérieure, CNRS (UMR 8551), Université P. et M. Curie, Université D. Diderot, 75231 Paris Cedex 05, France
²Lehrstuhl für Angewandte Festkörperphysik, Ruhr-Universität Bochum, NABF 03/249a, Universitätsstrasse 150, 44780 Bochum, Germany
³Semiconductor Physics, Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge CB3 0HE, United Kingdom 

Pulses from an actively modelocked terahertz quantum cascade laser are fully characterized using an optical sampling technique to detect the total instantaneous terahertz intensity. By triggering the quantum cascade laser electronics with a femtosecond laser, we are able to measure both the formation of modelocked pulses and the quasi-steady state. The dependence of the pulse width on the modulation power and drive current are investigated. At low drive currents, we measure transform-limited gaussian-shaped pulses with a FWHM of 19 ps