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Optical communications-based platform uses Uni-Travelling-Carrier Photodiode for ultra-high resolution software-defined THz spectroscopy and reveals LiYF4:Ho intrinsic spectral line shape
preprintposted on 2023-11-30, 18:57 authored by Rodolfo I. Hermans, Haymen Shams, James P. Seddon, Alwyn J. Seeds, Gabriel Aeppli
High resolution (900 Hz full-width at half maximum) frequency domain spectroscopy near 0.2Terahertz is achieved using an exact frequency spacing comb-source in the optical communications band, filtering and photo-mixing in a custom Uni-Travelling-Carrier Photodiode (UTC-PD) for THz signal generation and coherent down-conversion for detection. Via time domain modulation of one of the comb lines, a fully controllable spectrometer can be defined in software, and this principle is demonstrated for magnetic field-free readout of the electronuclear spectrum for the Ho ions in \lihof, a material often used for demonstration experiments in quantum science. In particular, homogeneous and inhomogeneous contributions to the spectrum are readily separated.