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(a) Scheme of our THz time-domain ellipsometer. The incoming polarization is set to either p or s polarization by means of a wire-grid polarizer. After reflection off the sample, the transient THz electric field is projected onto the analyzer direction and finally detected by electrooptic sampling. (b) Typical p- and s-polarized THz waveforms after reflection off the gold reference mirror. (c) Same as (b) yet with the reference mirror replaced by an STO sample. The phase shift between sample and reference waves arises from a small sample displacement.
(a) Power spectra of the p-polarized THz pulses reflected from pure STO and reference mirror. (b) Approximate p-polarization reflectance spectra of Nb:STO at various Nb-dopant densities .
(a) Measured ellipsometric angles and at . Error bars are the result of eight repeated measurements, each including a change between sample and reference mirror. (b) Real and imaginary part of the dielectric function as extracted from the data of (a) using Eq. (4). Solid lines represent a model fit with Eq. (5). Inset: extracted squared plasma frequency versus dopant density . Solid line is a linear fit.
Values of LO and TO phonon frequencies of pure STO extracted from this experiment along with literature values. The obtained is in agreement with Ref. 25.
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