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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.


(a) Optical microscope images of H-dipole structure and SEM of the fabricated nano-electrodes. (b) Schematic of the THz-TDS system used in this study.
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f1: (a) Optical microscope images of H-dipole structure and SEM of the fabricated nano-electrodes. (b) Schematic of the THz-TDS system used in this study.

Mentions: We designed three kinds of metallic nano-electrodes and integrated them with the conventional H-dipole shaped THz PCAs. The optical microscope image of the H-dipole structure and the SEM images of each nanostructure are shown in Fig. 1(a), designated by nano-gap (NG), nano-electrode (NE), and shifted nano-gap (SNG) structure. The nano-electrodes are based on nano-fingers of 200 nm periods to maximize the generation of plasmonic photocarriers along both sides of the nano-fingers23. The gap between electrodes was set at 200 nm and 3 μm for the NG structure and the NE structure, respectively. In the NE structure, the intermediate region acts as an absorption layer for the ordinary photo-absorption. The SNG structure is designed with a 1-μm wide inter-digit region by alternatively shifting the nano-fingers of the NG structure in the parallel direction to form an inter-digit region. The distribution of plasmonic carriers and bias field then becomes spatially coincident in the inter-digit region to collect the plasmonic carriers more efficiently. A reference PCA of the same geometry was fabricated without nano-fingers. All of the PCAs were fabricated on an Fe-doped semi-insulating GaAs wafer. For THz detection, we fabricated another H-shaped PCA on a low-temperature grown GaAs of sub-picosecond carrier lifetime.


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)

(a) Optical microscope images of H-dipole structure and SEM of the fabricated nano-electrodes. (b) Schematic of the THz-TDS system used in this study.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f1: (a) Optical microscope images of H-dipole structure and SEM of the fabricated nano-electrodes. (b) Schematic of the THz-TDS system used in this study.
Mentions: We designed three kinds of metallic nano-electrodes and integrated them with the conventional H-dipole shaped THz PCAs. The optical microscope image of the H-dipole structure and the SEM images of each nanostructure are shown in Fig. 1(a), designated by nano-gap (NG), nano-electrode (NE), and shifted nano-gap (SNG) structure. The nano-electrodes are based on nano-fingers of 200 nm periods to maximize the generation of plasmonic photocarriers along both sides of the nano-fingers23. The gap between electrodes was set at 200 nm and 3 μm for the NG structure and the NE structure, respectively. In the NE structure, the intermediate region acts as an absorption layer for the ordinary photo-absorption. The SNG structure is designed with a 1-μm wide inter-digit region by alternatively shifting the nano-fingers of the NG structure in the parallel direction to form an inter-digit region. The distribution of plasmonic carriers and bias field then becomes spatially coincident in the inter-digit region to collect the plasmonic carriers more efficiently. A reference PCA of the same geometry was fabricated without nano-fingers. All of the PCAs were fabricated on an Fe-doped semi-insulating GaAs wafer. For THz detection, we fabricated another H-shaped PCA on a low-temperature grown GaAs of sub-picosecond carrier lifetime.

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.