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Experimental setup. The scheme of the sandwich structure is shown in the inset.
(a) Spectra and (b) oscillograms of the terahertz field generated by 50 fs laser pulse with 5 μJ energy in the sandwich structure with b = 0 (solid curve) and b = ∞ (dotted curve). (c) Theoretically calculated spectra for the corresponding b and laser pulse duration.
(a) Normalized terahertz energy as a function of air gap b for 50 fs laser pulse (diamonds – experimental data, solid curve – theoretical calculation). (b) Conversion efficiency as a function of optical energy at b = 0 for pulse duration of 50 fs (crosses), 150 fs with positive and negative chirp (filled and empty circles, respectively), 220 fs (diamonds), and 400 fs (triangles) with negative chirp. In the inset, terahertz field spectra for 16 μJ laser pulse with positive (dashed) and negative (solid) chirp and duration of 150 fs.
Conversion efficiency as a function of laser pulse duration with positive (filled circles) and negative (empty circles) chirp for (a) 2 μJ and (b) 18 μJ pump energy. Dashed curves – theoretical calculation.
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