Schematic of THz pulse generation from nanopillars on a GaAs surface.
Cross-sectional SEM images of nanopillars on GaAs surfaces. The inserted numbers denote sample indices. Samples were numbered in order of nanopillar density. The insets show oblique SEM images (tilted by 30°).
(a) Time-domain waveforms of transmitted THz pulses and (b) reflection spectra around 790 nm of six samples and bare GaAs.
(a) Measured time-domain waveforms of THz pulses from six samples and bare GaAs and (b) their spectral amplitudes. The inset in (b) shows spectral amplitudes normalized to the peak amplitudes.
Temporal FWHMs ( ) and integrals of spectral amplitudes over all frequencies (Iamp ) of six samples and bare GaAs.
Laser coupling efficiency ( ) and internal conversion efficiency ( ) of six samples. Values were normalized to those for bare GaAs. Solid (open) circles denote normalized .
Measured time-domain waveforms of THz pulses from (a) bare GaAs and (b) sample , and (c) Iamp of the THz pulses when the power of the incident laser pulse is 50, 100, 150, 200, and 250 mW.
Summary of peak-to-peak (p-p) values, temporal and spectral FWHMs, and peak frequencies of THz pulses from six samples and bare GaAs.
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