Abstract-Reversible mode switching in Y-coupled terahertz lasers

Owen P. Marshall¹, Subhasish Chakraborty¹, Md Khairuzzaman¹, Harvey E. Beere², and David A. Ritchie²

¹School of Electrical and Electronic Engineering, University of Manchester, Manchester M13 9PL, United Kingdom
²Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge CB3 0HE, United Kingdom 

http://apl.aip.org/resource/1/applab/v102/i11/p111105_s1?isAuthorized=no 

Electrically independent terahertz (THz) quantum cascade lasers (QCLs) are optically coupled in a Y configuration. Dual frequency, electronically switchable emission is achieved in one QCL using an aperiodic grating, designed using computer-generated hologram techniques, and incorporated directly into the QCL waveguide by focussed ion beam milling. Multi-moded emission around 2.9 THz is inhibited, lasing instead occurring at switchable grating-selected frequencies of 2.88 and 2.92 THz. This photonic control and switching behaviour is selectively and reversibly transferred to the second, unmodified QCL via evanescent mode coupling, without the transfer of the inherent grating losses.

© 2013 American Institute of Physics

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