Figure III | Optical losses of potassium characterized by far-field spectroscopy. (IMAGE)
Caption
Figure III | Optical losses of potassium characterized by far-field spectroscopy. a, Real and imaginary parts of the dielectric functions (ε=ε1+iε2) of the potassium film measured with a spectroscopic ellipsometer. The inset illustration shows the schematic diagram of the measurement method. b-c, ε2 and -ε1/iε2 comparison with reported low-loss plasmonic metals (Ag, Na, ITO and (TMTTF)2SbF6), respectively. d, The propagation length and the γ retrieved from the propagation length method. The inset illustration shows the measured propagation length at different wavelengths of near-infrared on the potassium–quartz interface. The dotted line is the calculated propagation length based on the dielectric functions of the potassium film measured with a spectroscopic ellipsometer. e, The statistical data of γ retrieved from both SE and PL spectroscopic data. f, Comparisons of experimentally reported milestone γ values of mainstream state-of-the-art plasmonic materials in terms of the free carrier density and Fermi surface profiles.
Credit
Lin Zhou et al.
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