Wang, F, Maussang, K, Moumdji, S et al. (9 more authors) (2015) Generating ultrafast pulses of light from quantum cascade lasers. Optica, 2 (11). pp. 944-949. ISSN 2334-2536
Abstract
The generation of ultrashort pulses from quantum cascade lasers (QCLs) has proved to be challenging. It has been suggested that the ultrafast electron dynamics of these devices is the limiting factor for modelocking and hence pulse formation. Even so, clear modelocking of terahertz (THz) QCLs has been recently demonstrated but the exact mechanism for pulse generation is not fully understood. Here we demonstrate that the dominant factor necessary for active pulse generation is in fact the synchronization between the propagating electronic modulation and the generated THz pulse in the QCL. By using phase resolved detection of the electric field in QCLs embedded in metalmetal waveguides, we demonstrate that active modelocking requires the phase velocity of the microwave round trip modulation to equal the group velocity of the THz pulse. This allows the THz pulse to propagate in phase with the microwave modulation along the gain medium, permitting short pulse generation. Modelocking was performed on QCLs employing phonon depopulation active regions, permitting coherent detection of large gain bandwidths (500 GHz), and the generation of 11 ps pulses centered around 2.6 THz when the above ‘phase-matching’ condition is satisfied. This work brings an enhanced understanding of QCL modelocking and will permit new concepts to be explored to generate shorter and more intense pulses from mid-infrared, as well as THz, QCLs.
Metadata
Item Type: | Article |
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Authors/Creators: |
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Copyright, Publisher and Additional Information: | (c) 2015, Optical Society of America. This paper was published in Optica and is made available as an electronic reprint with the permission of OSA. The paper can be found at the following URL on the OSA website: http://dx.doi.org/10.1364/OPTICA.2.000944. Systematic or multiple reproduction or distribution to multiple locations via electronic or other means is prohibited and is subject to penalties under law. |
Dates: |
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Institution: | The University of Leeds |
Academic Units: | The University of Leeds > Faculty of Engineering & Physical Sciences (Leeds) > School of Electronic & Electrical Engineering (Leeds) > Pollard Institute (Leeds) |
Funding Information: | Funder Grant number EU - European Union 247375 Royal Society WM110032 EPSRC EP/J017671/1 |
Depositing User: | Symplectic Publications |
Date Deposited: | 04 Nov 2015 16:52 |
Last Modified: | 11 Feb 2019 13:21 |
Published Version: | https://doi.org/10.1364/OPTICA.2.000944 |
Status: | Published |
Publisher: | Optical Society of America |
Identification Number: | 10.1364/OPTICA.2.000944 |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:91489 |