High-speed modulation of a terahertz quantum cascade laser by coherent acoustic phonon pulses

The fast modulation of lasers is a fundamental requirement for applications in optical communications, high-resolution spectroscopy and metrology. In the terahertz-frequency range, the quantum-cascade laser (QCL) is a high-power source with the potential for high-frequency modulation. However, conve...

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Bibliographic Details
Published in:Nature communications 2020-02, Vol.11 (1), p.835-835, Article 835
Main Authors: Dunn, Aniela, Poyser, Caroline, Dean, Paul, Demić, Aleksandar, Valavanis, Alexander, Indjin, Dragan, Salih, Mohammed, Kundu, Iman, Li, Lianhe, Akimov, Andrey, Davies, Alexander Giles, Linfield, Edmund, Cunningham, John, Kent, Anthony
Format: Article
Language:English
Subjects:
639/624/1020/1092
639/624/1111/1115
639/624/400/561
Acoustic emission
Acoustic properties
Acoustics
Amplitude modulation
Frequency dependence
Frequency modulation
Frequency ranges
Humanities and Social Sciences
Lasers
multidisciplinary
Perturbation methods
Perturbation theory
Phonons
Pulse amplitude
Quantum cascade lasers
Science
Science (multidisciplinary)
Spectroscopy
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Summary:The fast modulation of lasers is a fundamental requirement for applications in optical communications, high-resolution spectroscopy and metrology. In the terahertz-frequency range, the quantum-cascade laser (QCL) is a high-power source with the potential for high-frequency modulation. However, conventional electronic modulation is limited fundamentally by parasitic device impedance, and so alternative physical processes must be exploited to modulate the QCL gain on ultrafast timescales. Here, we demonstrate an alternative mechanism to modulate the emission from a QCL device, whereby optically-generated acoustic phonon pulses are used to perturb the QCL bandstructure, enabling fast amplitude modulation that can be controlled using the QCL drive current or strain pulse amplitude, to a maximum modulation depth of 6% in our experiment. We show that this modulation can be explained using perturbation theory analysis. While the modulation rise-time was limited to ~800 ps by our measurement system, theoretical considerations suggest considerably faster modulation could be possible. The typical electronic modulation of terahertz quantum cascade lasers is fundamentally limited at fast timescales by device properties. Here the authors propose and study an alternative, acoustic mechanism for modulating such THz QCLs at high speed.
ISSN:2041-1723
2041-1723
DOI:10.1038/s41467-020-14662-w