Influence of electric and magnetic fields on THz radiation

Zhang, Xicheng; Jin, Yanping; Kingsley, L.E.; Weiner, M.

doi:10.1063/1.109324

Cited by 24 publications

(8 citation statements)

References 8 publications

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“…The radiated THz field is proportional to the optical pump power and is due to a combination of OR, 176,242 bulk DFG 243 and photocarrier acceleration in the surface field of the semiconductor. 244,245 T-ray emission from semiconductor surfaces is influenced by the magnetic field surrounding the emitter, 246,247 which can be used to switch or enhance the generation efficiency. 248~252 T-ray emission from an unbiased GaAs wafer in a switchable magnetic field is shown in Fig.…”

Section: Pulsed Photomixingmentioning

confidence: 99%

T-Ray Sensing and Imaging

Mickan

Zhang

2003

Int. J. Hi. Spe. Ele. Syst.

110

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Terahertz (THz) radiation occupies part of the electromagnetic spectrum between the infrared and microwave bands. Until recently, technology at THz frequencies was underdeveloped compared to the rest of the electromagnetic spectrum, leaving a gap between millimeter waves and the far-infrared (FIR). In the past decade, interest in the THz gap has been increased by the development of ultrafast laser-based T-ray systems and their demonstration of diffraction-limited spatial resolution, picosecond temporal resolution, DC-THz spectral bandwidth and signal-to-noise ratios above 10 4 . This chapter reviews the development, the state of the art and the applications of T-ray spectrometers. Continuous-wave (CW) THz-frequency sources and detectors are briefly introduced in comparison to ultrafast pulsed THz systems. An emphasis is placed on experimental applications of T-rays to sensing and imaging, with a view to the continuing advance of technologies and applications in the THz band.

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Section: Pulsed Photomixingmentioning

confidence: 99%

T-Ray Sensing and Imaging

Mickan

Zhang

2003

Int. J. Hi. Spe. Ele. Syst.

110

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“…However this limitation can be overcome by using a magnetic field to change the direction of the transient current. 5 Recently, Sarakura et al 6 have reported a substantial enhancement of the efficiency of THz generation at bare InAs surfaces by a moderate magnetic field. They claimed average emitted THz powers of ϳ0.7 mW using a 1 W average power Ti-sapphire pump laser.…”

Section: Introductionmentioning

confidence: 99%

Terahertz emission from GaAs and InAs in a magnetic field

et al. 2001

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We have studied terahertz ͑THz͒ emission from InAs and GaAs in a magnetic field, and find that the emitted radiation is produced by coupled cyclotron-plasma charge oscillations. Ultrashort pulses of THz radiation were produced at semiconductor surfaces by photoexcitation with a femtosecond Ti-sapphire laser. We recorded the integrated THz power and the THz emission spectrum as a function of magnetic field at fields up to 5.5 T, and as function of temperature for Tϭ10-280 K. The maximum observed THz power is ϳ1.6ϫ10 Ϫ13 J/pulse ͑12 W average power͒ from n-InAs (1.8ϫ10 16 cm Ϫ3 ͒ at Bϭ3.2 T. We compare our results to semiclassical models of magnetoplasma oscillations of bulk free carriers and damped motion of free carriers in a twodimensional electron gas. The bulk model describes THz emission from n-GaAs at all magnetic fields, and InAs at Bϭ0. It fails to describe THz emission from InAs at nonzero magnetic fields. We show that a model including both bulk plasma oscillations and THz emission from a surface accumulation layer describes THz emission from InAs in a moderate magnetic field, but this model does not completely describe emission at fields ͉B͉Ͼ1.0 T.

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“…When illuminated at 0° angle of incidence, little or no THz emission is therefore observed in the back-reflected direction, as mentioned earlier. The application of the magnetic-field creates a Lorentz force acting on the moving charges, which adds a vertical in-plane component to the current, and thus creates a vertically polarized THz electric-field component [15][16][17][18]. We note that historically, before the exact cause for the magnetic field-induced changes in THz emission for semiconductors was known, an enhancement factor was used to phenomenologically describe the magnetic-field induced changes in the emitted THz amplitude.…”

Section: Basal-plane Surface Illuminationmentioning

confidence: 99%

Terahertz generation from graphite

2009

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Generation of subpicosecond terahertz pulses is observed when graphite surfaces are illuminated with femtosecond near-infrared laser pulses. The nonlinear optical generation of THz pulses from graphite is unexpected since, in principle, the material possesses a centre of inversion symmetry. Experiments with highly oriented pyrolytic graphite crystals suggest that the THz radiation is generated by a transient photocurrent in a direction normal to the graphene planes, along the c-axis of the crystal. This is supported by magnetic-field induced changes in the THz electric-field polarization, and consequently, the direction of the photocurrent. We show that other forms of graphite, such as a pencil drawing on paper, are also capable of emitting THz pulses.

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Influence of electric and magnetic fields on THz radiation

Cited by 24 publications

References 8 publications

T-Ray Sensing and Imaging

T-Ray Sensing and Imaging

Terahertz emission from GaAs and InAs in a magnetic field

Terahertz generation from graphite

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