Analysis of terahertz pulses from large-aperture biased semi-insulating and arsenic-ion-implanted GaAs antennas

Chou, Rone-Hwa; Liu, Tze-An; Pan, Ci‐Ling

doi:10.1063/1.2967716

Cited by 11 publications

(4 citation statements)

References 29 publications

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“…Ion implantation is a more industry-compatible technique and its parameters (energy and dose) can be compared more reliably from machine to machine as compared to growth temperatures in low-temperature molecular-beam epitaxy systems. 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].…”

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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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 basic physics of ultrafast semiconductor switches is relatively well understood. Several recent studies [15][16][17][18][19] have investigated the physics underlying the PC antenna characteristics but there is still a need to establish a strong link between the THz instrumental response function ͑spectrum of the reference THz pulses͒ and the relaxation times extracted from time-resolved pump-probe measurements. [12][13][14] The overall response function of a time-domain THz spectroscopy system is often complicated by the influence of experimental conditions such as the laser excitation density, dimension of the detecting area and imaging characteristics of the optical system used to relay the pulses from the source through the sample to the detector.…”

Section: Photoexcited Carrier Relaxation Dynamics and Terahertz Respomentioning

confidence: 99%

Photoexcited carrier relaxation dynamics and terahertz response of photoconductive antennas made on proton bombarded GaAs materials

Savard

Allard

Bernier

et al. 2010

Journal of Applied Physics

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We present a model reproducing the instrumental response of a time-domain spectrometer that integrates photoconductive transmitter and receiver antennas made on identical proton-bombarded GaAs substrates. This model is used to determine the ultrafast capture time of the photoexcited carriers by the ion-bombardment-induced traps. A 0.5 ps capture time can be extracted for a low laser pump fluence of 0.66 J / cm 2 per pulse. This carrier trapping time gets longer as the pump fluence increases. This behavior is explained by a gradual filling of the traps that are distributed over a 1 m depth from the GaAs surface. This interpretation is supported by time-resolved measurements obtained on the same photoconductive material using both an 820 nm pump/ terahertz-probe transmission experiment and a degenerate 760 nm pump/probe reflectivity experiment. The differential transmission and reflectivity dynamics are reproduced using a biexponential function which correctly describes the photoexcited carrier relaxation and transport dynamics in this material. The strong agreement observed between these different measurements reinforces the validity of the theoretical model used to reproduce the instrumental response of the terahertz setup.

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“…With further researches, it has been gradually recognized the application prospects of terahertz wave in the fields of communications, medical, security and materials science [1][2][3][4][6][7][8][9][10][11][12] . At the present stage, the technology of THz pulses generated using linear photoconductivity antennas has been widely used.…”

Section: Introductionmentioning

confidence: 99%

The THz emission properties of GaAs photoconductive antenna with strong electric fields

Xue

2012

Isape2012

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The terahertz (THz) emission properties of GaAs photoconductive antennas with strong electric fields are discussed; the transient transport characteristics of non-equilibrium carriers (hot electrons) within the photoconductive antenna were comparatively analyzed. It is shown that there are significant differences in the average drift velocity variation with strong and weak electric field. In the initial phase, optical wave scattering is mainly caused by small-angle scattering, carriers are accelerated by ballistic transport to reach higher electron energy in a shorter time, and the transient drift-velocity quickly rises, which is a main reason of the stronger THz radiation.

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Analysis of terahertz pulses from large-aperture biased semi-insulating and arsenic-ion-implanted GaAs antennas

Cited by 11 publications

References 29 publications

Scalable Microstructured Photoconductive Terahertz Emitters

Scalable Microstructured Photoconductive Terahertz Emitters

Photoexcited carrier relaxation dynamics and terahertz response of photoconductive antennas made on proton bombarded GaAs materials

The THz emission properties of GaAs photoconductive antenna with strong electric fields

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