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Ultra-high-resolution software-defined photonic terahertz spectroscopy

Hermans, RI; Seddon, J; Shams, H; Ponnampalam, L; Seeds, AJ; Aeppli, G; (2020) Ultra-high-resolution software-defined photonic terahertz spectroscopy. Optica , 7 (10) p. 1445. 10.1364/optica.397506. Green open access

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A novel technique for high-resolution 1.5 µm photonics-enabled terahertz (THz) spectroscopy using software control of the illumination spectral line shape (SLS) is presented. The technique enhances the performance of a continuous-wave THz spectrometer to reveal previously inaccessible details of closely spaced spectral peaks. We demonstrate the technique by performing spectroscopy on LiYF4:Ho3+, a material of interest for quantum science and technology, where we discriminate between inhomogeneous Gaussian and homogeneous Lorentzian contributions to absorption lines near 0.2 THz. Ultra-high-resolution (<100 Hz full-width at half maximum) frequency-domain spectroscopy with quality factor Q > 2 × 109 is achieved using an exact frequency spacing comb source in the optical communications band, with a custom uni-traveling-carrier photodiode mixer and coherent down-conversion detection. Software-defined time-domain modulation of one of the comb lines is demonstrated and used to resolve the sample SLS and to obtain a magnetic field-free readout of the electronuclear spectrum for the Ho3+ ions in LiYF4:Ho3+. In particular, homogeneous and inhomogeneous contributions to the spectrum are readily separated. The experiment reveals previously unmeasured information regarding the hyperfine structure of the first excited state in the 5 I8 manifold complementing the results reported in Phys. Rev. B 94, 205132 (2016).

Type: Article
Title: Ultra-high-resolution software-defined photonic terahertz spectroscopy
Open access status: An open access version is available from UCL Discovery
DOI: 10.1364/optica.397506
Publisher version: http://dx.doi.org/10.1364/optica.397506
Language: English
Additional information: Published by The Optical Society under the terms of the Creative Commons Attribution 4.0 License. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.
UCL classification: UCL
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science > Dept of Electronic and Electrical Eng
URI: https://discovery.ucl.ac.uk/id/eprint/10112836
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