1Ultra-Intense Laser Laboratory, Advanced Photonics Research Institute, GIST, Gwangju 500-712, South Korea
2Department of Electronics and Radio Engineering, Institute for Laser Engineering, Kyung Hee University, Gyeonggi-do 446-701, South Korea
3Department of Physics, Chonnam National University, Gwangju 500-757, South Korea
4Center for Subwavelength Optics, Seoul 151-747, South Korea
2Department of Electronics and Radio Engineering, Institute for Laser Engineering, Kyung Hee University, Gyeonggi-do 446-701, South Korea
3Department of Physics, Chonnam National University, Gwangju 500-757, South Korea
4Center for Subwavelength Optics, Seoul 151-747, South Korea
We investigated the characteristics of terahertz pulses generated from antireflective GaAs surfaces with nanopillars under femtosecond laser excitation. Although the antireflective nanostructures contribute to the enhancement of free photocarrier excitation in GaAs, they could reduce the transient photocurrent density and advance the start time of the photocurrent decay. Thus, the relative amplitudes of the high-frequency spectral components of terahertz pulses increased, whereas the energies of the pulses decreased. However, we showed that thinly distributed nanopillar structures could generate a short terahertz pulse without a reduction in the pulse energy.
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