15 October 2012 Narrow linewidth tunable THz signal radiated by 1.55μm photomixing
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THz has become a wide field of investigation opening new opportunities in a growing number of domains of physics, chemistry, and biology. Among the different techniques existing today to generate THz fields, heterodyning two optical frequencies is a useful approach when tunability is required. Moreover, to address high-resolution spectroscopy or metrology applications, a key point is the achievement of a narrow linewidth source. To this aim, two-propagation-axis dual-frequency lasers have been already shown to provide narrow linewidth tunable beat notes up to 2 THz. We report in this paper the demonstration of a narrow linewidth THz radiation source based upon this laser. Indeed the beat note provided by the laser is sent into a unitravelling carrier photodiode (UTC-PD), and radiated by a transverseelectromagnetic- horn antenna (TEM-HA). All components operate at room temperature. The emitted THz signal is detected by a subharmonic mixer coupled to an electrical spectrum analyzer. The THz signal is observed and analyzed thanks to a heterodyne detection. The measured dynamic range is 75 dB at 282 GHz, 50 dB at 500 GHz, 35 dB at 700 GHz and decreases to 20 dB at 1 THz. The decrease is due to the UTC-PD efficiency and conversion losses in the sub-harmonic mixer. The measured linewidth is better than 30 kHz at any frequency from DC to 1 THz.
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Antoine Rolland, Antoine Rolland, Guillaume Ducournau, Guillaume Ducournau, Goulc'hen Loas, Goulc'hen Loas, Alexandre Beck, Alexandre Beck, Fabio Pavanello, Fabio Pavanello, Emilien Peytavit, Emilien Peytavit, Tahsin Akalin, Tahsin Akalin, Mohamed Zaknoune, Mohamed Zaknoune, Jean-François Lampin, Jean-François Lampin, Marc Brunel, Marc Brunel, François Bondu, François Bondu, Marc Vallet, Marc Vallet, Mehdi Alouini, Mehdi Alouini, } "Narrow linewidth tunable THz signal radiated by 1.55μm photomixing", Proc. SPIE 8496, Terahertz Emitters, Receivers, and Applications III, 84960C (15 October 2012); doi: 10.1117/12.929738; https://doi.org/10.1117/12.929738

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