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Bias field tailored plasmonic nano-electrode for high-power terahertz photonic devices.

Moon K, Lee IM, Shin JH, Lee ES, Kim N, Lee WH, Ko H, Han SP, Park KH - Sci Rep (2015)

Bottom Line: Photoconductive antennas with nano-structured electrodes and which show significantly improved performances have been proposed to satisfy the demand for compact and efficient terahertz (THz) sources.Plasmonic field enhancement was previously considered the dominant mechanism accounting for the improvements in the underlying physics.Our findings will pave the way for new perspectives in the design and analysis of plasmonic nano-structures for more efficient THz photonic devices.

View Article: PubMed Central - PubMed

Affiliation: THz Photonics Creative Research Center, Future Research Creative Laboratory, Electronics and Telecommunications Research Institute (ETRI), Daejeon 305-700, Korea.

ABSTRACT
Photoconductive antennas with nano-structured electrodes and which show significantly improved performances have been proposed to satisfy the demand for compact and efficient terahertz (THz) sources. Plasmonic field enhancement was previously considered the dominant mechanism accounting for the improvements in the underlying physics. However, we discovered that the role of plasmonic field enhancement is limited and near-field distribution of bias field should be considered as well. In this paper, we clearly show that the locally enhanced bias field due to the size effect is much more important than the plasmonic enhanced absorption in the nano-structured electrodes for the THz emitters. Consequently, an improved nano-electrode design is presented by tailoring bias field distribution and plasmonic enhancement. Our findings will pave the way for new perspectives in the design and analysis of plasmonic nano-structures for more efficient THz photonic devices.

No MeSH data available.


Relative power of the nano-PCAs for optical excitation of (a) perpendicular polarization, and (b) parallel polarization. (c) THz power ratio between the perpendicular and the parallel polarization of the optical excitation.
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f2: Relative power of the nano-PCAs for optical excitation of (a) perpendicular polarization, and (b) parallel polarization. (c) THz power ratio between the perpendicular and the parallel polarization of the optical excitation.

Mentions: The THz pulses emitting from each PCA were measured using the THz-TDS system depicted in Fig. 1(b). (The details of the experimental setup are discussed in the methods.) To vary the polarization and power of the optical excitation without distorting optical alignment, for experimental accuracy, we inserted a linear polarizer, a quarter-wavelength waveplate, and a variable optical attenuator. In this study, we measured the peak-to-peak THz current (ITHz) as a function of the optical excitation power (Popt) for the perpendicular and parallel polarizations of which definitions are depicted in Fig. 1(a). The AC bias voltage was set to 8 Vpp. From these results, we derived the ratios of the THz power to that from the reference PCA for each structure for perpendicular and parallel polarizations, as shown in Fig. 2(a,b). The ratios between these two polarizations are depicted in Fig. 2(c). For the reference measurement, the polarization was set to parallel for better emission efficiency. Time-domain curves and spectra obtained at 10 mW of Popt are shown in Fig. S1, and the absolute values of the measured ITHz are shown in Fig. S2 (see Supporting Information).


Bias field tailored plasmonic nano-electrode for high-power terahertz photonic devices.

Moon K, Lee IM, Shin JH, Lee ES, Kim N, Lee WH, Ko H, Han SP, Park KH - Sci Rep (2015)

Relative power of the nano-PCAs for optical excitation of (a) perpendicular polarization, and (b) parallel polarization. (c) THz power ratio between the perpendicular and the parallel polarization of the optical excitation.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4561887&req=5

f2: Relative power of the nano-PCAs for optical excitation of (a) perpendicular polarization, and (b) parallel polarization. (c) THz power ratio between the perpendicular and the parallel polarization of the optical excitation.
Mentions: The THz pulses emitting from each PCA were measured using the THz-TDS system depicted in Fig. 1(b). (The details of the experimental setup are discussed in the methods.) To vary the polarization and power of the optical excitation without distorting optical alignment, for experimental accuracy, we inserted a linear polarizer, a quarter-wavelength waveplate, and a variable optical attenuator. In this study, we measured the peak-to-peak THz current (ITHz) as a function of the optical excitation power (Popt) for the perpendicular and parallel polarizations of which definitions are depicted in Fig. 1(a). The AC bias voltage was set to 8 Vpp. From these results, we derived the ratios of the THz power to that from the reference PCA for each structure for perpendicular and parallel polarizations, as shown in Fig. 2(a,b). The ratios between these two polarizations are depicted in Fig. 2(c). For the reference measurement, the polarization was set to parallel for better emission efficiency. Time-domain curves and spectra obtained at 10 mW of Popt are shown in Fig. S1, and the absolute values of the measured ITHz are shown in Fig. S2 (see Supporting Information).

Bottom Line: Photoconductive antennas with nano-structured electrodes and which show significantly improved performances have been proposed to satisfy the demand for compact and efficient terahertz (THz) sources.Plasmonic field enhancement was previously considered the dominant mechanism accounting for the improvements in the underlying physics.Our findings will pave the way for new perspectives in the design and analysis of plasmonic nano-structures for more efficient THz photonic devices.

View Article: PubMed Central - PubMed

Affiliation: THz Photonics Creative Research Center, Future Research Creative Laboratory, Electronics and Telecommunications Research Institute (ETRI), Daejeon 305-700, Korea.

ABSTRACT
Photoconductive antennas with nano-structured electrodes and which show significantly improved performances have been proposed to satisfy the demand for compact and efficient terahertz (THz) sources. Plasmonic field enhancement was previously considered the dominant mechanism accounting for the improvements in the underlying physics. However, we discovered that the role of plasmonic field enhancement is limited and near-field distribution of bias field should be considered as well. In this paper, we clearly show that the locally enhanced bias field due to the size effect is much more important than the plasmonic enhanced absorption in the nano-structured electrodes for the THz emitters. Consequently, an improved nano-electrode design is presented by tailoring bias field distribution and plasmonic enhancement. Our findings will pave the way for new perspectives in the design and analysis of plasmonic nano-structures for more efficient THz photonic devices.

No MeSH data available.