Mapping the distribution of photo-currents responsible for generation of terahertz pulses at semiconductor surfaces

Mueckstein, Raimund; Hatem, Osama; Natrella, Michele; Freeman, Joshua R.; Graham, CS; Renaud, Cyril C.; Seeds, A.J.; Linfield, E. H.; Davies, A. G.; Cannard, PJ; Robertson, M. J.; Moodie, DG; Mitrofanov, Oleg

doi:10.1109/irmmw-thz.2014.6956034

Cited by 2 publications

(2 citation statements)

References 6 publications

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“…A recent study of the field distribution of THz pulses generated at InGaAs surfaces photo-excited at normal incidence confirmed the significance of this mechanism23, which has been corroborated with Monte Carlo simulations25. For a Gaussian beam incident on the semiconductor surface, the transient dipole moments are arranged radially and the radiated THz pulse therefore is expected to be radially-polarized with the intensity profile in a doughnut shape26 similar to the TEM mode of the coaxial metallic waveguide.…”

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confidence: 65%

Generation of radially-polarized terahertz pulses for coupling into coaxial waveguides

Navarro‐Cía

Liu

et al. 2016

Sci Rep

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Coaxial waveguides exhibit no dispersion and therefore can serve as an ideal channel for transmission of broadband THz pulses. Implementation of THz coaxial waveguide systems however requires THz beams with radially-polarized distribution. We demonstrate the launching of THz pulses into coaxial waveguides using the effect of THz pulse generation at semiconductor surfaces. We find that the radial transient photo-currents produced upon optical excitation of the surface at normal incidence radiate a THz pulse with the field distribution matching the mode of the coaxial waveguide. In this simple scheme, the optical excitation beam diameter controls the spatial profile of the generated radially-polarized THz pulse and allows us to achieve efficient coupling into the TEM waveguide mode in a hollow coaxial THz waveguide. The TEM quasi-single mode THz waveguide excitation and non-dispersive propagation of a short THz pulse is verified experimentally by time-resolved near-field mapping of the THz field at the waveguide output.

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confidence: 65%

Generation of radially-polarized terahertz pulses for coupling into coaxial waveguides

Navarro‐Cía

Liu

et al. 2016

Sci Rep

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“…The radiated field nevertheless is expected in directions off the optical axis with a maximum in the range of 20°-50° depending on the spatial profile of the optical excitation. The angular emission pattern can be measured in our experimental system and used to verify the model [23].…”

Section: B Angular Emission Pattern In the Far-field Zonementioning

confidence: 99%

Near-Field Analysis of Terahertz Pulse Generation From Photo-Excited Charge Density Gradients

Mueckstein

Natrella

Hatem

et al. 2015

IEEE Trans. THz Sci. Technol.

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Abstract-Excitation of photo-current transients at semiconductor surfaces by sub-picosecond optical pulses gives rise to emission of electromagnetic pulses of terahertz (THz) frequency radiation. To correlate the THz emission with the photo-excited charge density distribution and the photo-current direction, we mapped near-field and far-field distributions of the generated THz waves from GaAs and Fe-doped InGaAs surfaces. The experimental results show that the charge dynamics in the plane of the surface can radiate substantially stronger THz pulses than the charge dynamics in the direction normal to the surface, which is generally regarded as the dominant origin of the emission.

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Mapping the distribution of photo-currents responsible for generation of terahertz pulses at semiconductor surfaces

Cited by 2 publications

References 6 publications

Generation of radially-polarized terahertz pulses for coupling into coaxial waveguides

Generation of radially-polarized terahertz pulses for coupling into coaxial waveguides

Near-Field Analysis of Terahertz Pulse Generation From Photo-Excited Charge Density Gradients

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