Intense Terahertz Pulses from Large-Aperture Antenna with Interdigitated Electrodes

Hattori, Toshiaki; Egawa, Kazuhiro; Ookuma, Shin-ichi; Itatani, Taro

doi:10.1143/jjap.45.l422

Cited by 59 publications

(36 citation statements)

References 14 publications

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“…By inverting the bias voltage applied to the central unit, coherent synthesis of output from the seven units leads to annular profiles and smaller spot sizes of the focused THz field. Putting the present results together with the previous observation on time-domain coherent superposition [1], it is shown that spatio-temporal coherent systhesis can be performed using THz emitter arrays.…”

supporting

confidence: 76%

Coherent synthesis of THz wave profiles

Hattori

Masuda

Itatani

et al. 2007

2007 Joint 32nd International Conference on Infrared and Millimeter Waves and the 15th International Conference on Terahertz El

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Coherent synthesis of THz wave spatial profiles was observed using real-time THz imaging. We used an array of photoconductive antennas pumped by femtosecond optical pulses as a THz wave source. Emitted THz pulses were focused and the spatial profile on the focal plane, which is a coherent superposition of output from each unit, was observed by realtime THz imaging using the EO sampling method. By inverting the bias voltage applied to the central unit of the antenna array, a super-resolution effect was observed, where the THz spot sizes was smaller than when a voltage was applied to all the unit in the same direction.

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supporting

confidence: 76%

Coherent synthesis of THz wave profiles

Hattori

Masuda

Itatani

et al. 2007

2007 Joint 32nd International Conference on Infrared and Millimeter Waves and the 15th International Conference on Terahertz El

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“…In recent years, improvement in the various fields of THz research has been achieved with the development of an advanced laser source with femtosecond ( fs ) pulses123. The observation of THz waves between the microwave and infrared regions has motivated further expansion in research directions not previously considered, such as carrier dynamics with ~ ps lifetimes and applications in biomedical research using extremely low energy (~ meV).…”

mentioning

confidence: 99%

Strongly Enhanced THz Emission caused by Localized Surface Charges in Semiconducting Germanium Nanowires

Lee

Won

Bae

et al. 2013

Sci Rep

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A principal cause of THz emission in semiconductor nanostructures is deeply involved with geometry, which stimulates the utilization of indirect bandgap semiconductors for THz applications. To date, applications for optoelectronic devices, such as emitters and detectors, using THz radiation have focused only on direct bandgap materials. This paper reports the first observation of strongly enhanced THz emission from Germanium nanowires (Ge NWs). The origin of THz generation from Ge NWs can be interpreted using two terms: high photoexcited electron-hole carriers (Δn) and strong built-in electric field (Eb) at the wire surface based on the relation . The first is related to the extensive surface area needed to trigger an irradiated photon due to high aspect ratio. The second corresponds to the variation of Fermi-level determined by confined surface charges. Moreover, the carrier dynamics of optically excited electrons and holes give rise to phonon emission according to the THz region.

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“…This is similar to the behavior of large aperture emitters [32]. In another experiment, seven emitters of 1 cm 2 area have been combined to an array of large enough area to reduce the saturation effects by expanding the NIR beam [119]. However, only 1 kV/cm output fields could be achieved, possibly because of difficulties to focus the THz beam tightly.…”

Section: Operation Of Scalable Microstructured Emitters With Amplifiementioning

confidence: 54%

Scalable Microstructured Photoconductive Terahertz Emitters

Winnerl

2011

J Infrared Milli Terahz Waves

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The development of scalable emitters for pulsed broadband terahertz (THz) radiation is reviewed. Their large active area in the 1 -100 mm 2 range allows for using the full power of state-of-the-art femtosecond lasers for excitation of charge carriers. Large fields for acceleration of the photogenerated carriers are achieved at moderate voltages by interdigitated electrodes. This results in efficient emission of single-cycle THz waves. THz field amplitudes in the range of 300 V/cm and 17 kV/cm are reached for excitation with 10 nJ pulses from Ti:sapphire oscillators and for excitation with 5 μJ pulses from amplified lasers, respectively. The corresponding efficiencies for conversion of near-infrared to THz radiation are 2.5×10 -4 (oscillator excitation) and 2×10 -3 (amplifier excitation). In this article the principle of operation of scalable emitters is explained and different technical realizations are described. We demonstrate that the scalable concept provides freedom for designing optimized antenna patterns for different polarization modes. In particular emitters for linearly, radially and azimuthally polarized radiation are discussed. The success story of photoconductive THz emitters is closely linked to the development of mode-locked Ti: sapphire lasers. GaAs is an ideal photoconductive material for THz emitters excited with Ti: sapphire lasers, which are widely used in research laboratories. For many applications, especially in industrial environments, however, fiber-based lasers are strongly preferred due to their lower cost, compactness and extremely stable operation. Designing photoconductive emitters on InGaAs materials, which have a low enough energy gap for excitation with fiber lasers, is challenging due to the electrical properties of the materials. We discuss why the challenges are even larger for microstructured THz emitters as compared to conventional photoconductive antennas and present first results of emitters suitable for excitation with ytterbium-based fiber lasers. Furthermore an alternative concept, namely the lateral photo-Dember emitter, is presented. Due to the strong THz output scalable emitters are well suited for THz systems with fast data acquisition. Here the application of scalable emitters in THz spectrometers without mechanical delay stages, providing THz spectra with 1 GHz spectral resolution and a signal-to-noise ratio of 37 dB within 1 s, is

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Intense Terahertz Pulses from Large-Aperture Antenna with Interdigitated Electrodes

Cited by 59 publications

References 14 publications

Coherent synthesis of THz wave profiles

Coherent synthesis of THz wave profiles

Strongly Enhanced THz Emission caused by Localized Surface Charges in Semiconducting Germanium Nanowires

Scalable Microstructured Photoconductive Terahertz Emitters

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