Generation and Detection of THz Radiation With Scalable Antennas Based on GaAs Substrates With Different Carrier Lifetimes

Winnerl, Stephan; Peter, F.; Nitsche, S.; Dreyhaupt, A.; Zimmermann, B.; Wagner, Martin; Schneider, Harald; Helm, M.; Köhler, K.

doi:10.1109/jstqe.2007.910104

Cited by 43 publications

(31 citation statements)

References 34 publications

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“…In figure 4, the simulated signal amplitude for two trap densities is shown at fluences from 0.2 to 200 μJ cm −2 . For the low trap density sample, there is a clear sub-linear behaviour (the dotted curve has a gradient of 1), similar to that reported in previous experimental studies [18,42]. The high trap density simulation has an almost linear dependence for low fluences (<10 μJ cm −2 ), then a superlinear increase for intermediate fuences (between 10 and 60 μJ cm −2 ) and a sub-linear dependence for high fluences.…”

Section: Influence Of Fluencesupporting

confidence: 86%

Simulation of fluence-dependent photocurrent in terahertz photoconductive receivers

Castro-Camus

Johnston

Lloyd‐Hughes

2012

Semicond. Sci. Technol.

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A semi-classical Monte Carlo simulation of carrier dynamics in photoconductive detectors of terahertz (THz) radiation is presented. We have used this simulation to elucidate the importance of carrier trapping in the operation of photoconductive detectors. Simulations of the detection of single-cycle THz pulses by photoconductive antennas based on GaAs with trap densities between 2 × 10 17 and 2 × 10 18 cm −3 are presented. We show that the high frequency (>1 THz) spectral response of photoconductive devices decreases with increasing excitation fluence. Our simulations reveal that this effect is a direct consequence of the saturation of trapping centres

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Section: Influence Of Fluencesupporting

confidence: 86%

Simulation of fluence-dependent photocurrent in terahertz photoconductive receivers

Castro-Camus

Johnston

Lloyd‐Hughes

2012

Semicond. Sci. Technol.

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“…Very short carrier lifetimes are mostly important for the frequency response of THz detectors, for emitters the THz frequency spectrum is determined mostly by the laser pulse duration and the material absorption. The overall conversion efficiency of emitters fabricated from LT-GaAs and compensated semiinsulating GaAs with nanosecond carrier lifetime is comparable [36].…”

Section: 2materials Considerationsmentioning

confidence: 93%

Intense ultrashort terahertz pulses: generation and applications

Hoffmann¹,

Fülöp²

2011

J. Phys. D: Appl. Phys.

332

215

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Ultrashort terahertz pulses derived from femtosecond table-top sources have become a valuable tool for time-resolved spectroscopy during the last two decades. Until recently, the pulse energies and field strengths of these pulses have been generally too low to allow for the use as pump pulses or the study of nonlinear effects in the terahertz range. In this review article we will describe methods of generation of intense single cycle terahertz pulses with emphasis on optical rectification using the tilted-pulse-front pumping technique. We will also discuss some applications of these intense pulses in the emerging field of nonlinear terahertz spectroscopy.

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“…The fact that carriers are already trapped while the excitation pulse is applied makes this material unfavorable for pulsed THz emitters. The emission from our ion-implanted emitters was comparable to the emission from the LT-GaAs based scalable emitter [92]. The previously mentioned onset of saturation at higher carrier densities for LT-GaAs can not be exploited here, since the scalable emitters are operated in a regime where saturation is negligable.…”

Section: Gaas Substrates With Low Carrier Lifetimementioning

confidence: 76%

“…Different ions (H + , N + , O + , As + ) have been implanted into GaAs and surface field emitters and various photoconductive emitter antennas have been demonstrated based on these materials [84,[87][88][89][90][91]. Scalable emitters have been fabricated on GaAs implanted with N + and As + with various doses and also on LT-GaAs [92]. In Fig.…”

Section: Gaas Substrates With Low Carrier Lifetimementioning

confidence: 99%

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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Generation and Detection of THz Radiation With Scalable Antennas Based on GaAs Substrates With Different Carrier Lifetimes

Cited by 43 publications

References 34 publications

Simulation of fluence-dependent photocurrent in terahertz photoconductive receivers

Simulation of fluence-dependent photocurrent in terahertz photoconductive receivers

Intense ultrashort terahertz pulses: generation and applications

Scalable Microstructured Photoconductive Terahertz Emitters

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