Title: All-optical adaptive control of quantum cascade random lasers
Authors: Schönhuber, Sebastian 
Bachelard, Nicolas 
Limbacher, Benedikt  
Kainz, Martin Alexander 
Andrews, Aaron Maxwell  
Detz, Hermann 
Strasser, Gottfried  
Darmo, Juraj 
Rotter, Stefan  
Unterrainer, Karl 
Category: Original Research Article
Issue Date: 2-Nov-2020
Journal: Nature Communications 
ISSN: 2041-1723
Spectral fingerprints of molecules are mostly accessible in the terahertz (THz) and mid-infrared ranges, such that efficient molecular-detection technologies rely on broadband coherent light sources at such frequencies. If THz Quantum Cascade Lasers can achieve octave-spanning bandwidth, their tunability and wavelength selectivity are often constrained by the geometry of their cavity. Here we introduce an adaptive control scheme for the generation of THz light in Quantum Cascade Random Lasers, whose emission spectra are reshaped by applying an optical field that restructures the permittivity of the active medium. Using a spatial light modulator combined with an optimization procedure, a beam in the near infrared (NIR) is spatially patterned to transform an initially multi-mode THz random laser into a tunable single-mode source. Moreover, we show that local NIR illumination can be used to spatially sense complex near-field interactions amongst modes. Our approach provides access to new degrees of freedom that can be harnessed to create broadly-tunable sources with interesting potential for applications like self-referenced spectroscopy.
Keywords: Photonic devices; Quantum cascade lasers; Terahertz optics
DOI: 10.1038/s41467-020-19305-8
Organisation: E136 - Institut für Theoretische Physik 
E387 - Institut für Photonik 
E387-01 - Forschungsbereich Photonik 
License: CC BY 4.0 CC BY 4.0
Publication Type: Article
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