dc.description.abstract
Terahertz (THz) spectral range covers frequencies from 0.1 to 50 THz [1]. Due
to its photon energy, THz radiation is a powerful tool for low-energy excitations. The excitation of spin-waves [2], phonons [3; 4], and ionization of
excitons [5] are possible. Additionally, ultrafast spin dynamics can be investigated by the study of THz emission [6].
There are multiple sources to generate THz radiation. Firstly, photoconductive
antennas, which are used for linear THz spectroscopy with limited bandwidth
<6 THz [7; 8]. Secondly, organic crystals with a bandwidth from 1-10 THz
and a major detriment of having gaps in their emission spectrum [9]. Thirdly,
the lithium niobate crystal (LiNbO3) with a bandwidth of 0.1-2.5 THz creates
high peak amplitudes for non-linear THz spectroscopy [10; 11]. Lastly, the
spintronic terahertz emitter covers a range of 0.3-15 THz [12] and was recently
improved to match its peak amplitude to the commonly used LiNbO3 [13].
With regards to detection, usually, electro-optic sampling (EOS) using a pump-probe scheme is utilized [14]. With this, a multi-shot approach is used by which
the timing between the THz pump and probe is modified to measure the temporal change in the refractive index of the material, which is proportional to
the THz amplitude [15]. This approach has some disadvantages. The shot-to-shot fluctuations (noise) of the multiple sampling pulses may easily exceed
small signal amplitudes. Therefore, a long averaging time is necessary to obtain an acceptable signal-to-noise ratio. The single-shot EOS (SEOS) could
overcome these drawbacks because it requires only one probe pulse to measure
the time-resolved change in the refractive index of the material over the whole
duration of the THz pulse [17].
This work showcases the successful implementation of a single-shot approach
for broadband THz detection. The efficacy of this approach was ascertained
through a comparison with the established multi-shot EOS (MEOS) methodology. Furthermore, to gain deeper insights into the underlying dynamics at play, theoretical modeling of the SEOS technique was also carried
3
out. Collectively, these investigations provide a comprehensive understanding of the advantages and limitations offered by the SEOS approach in THz
detection.
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