Impact ionization dynamics in silicon by MV/cm THz fields

Tarekegne, Abebe Tilahun; Hirori, Hideki; Tanaka, Kōichiro; Iwaszczuk, Krzysztof; Jepsen, Peter Uhd

doi:10.1088/1367-2630/aa936b

Cited by 39 publications

(22 citation statements)

References 41 publications

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“…wafers in the beam path [47]. In the collimated beam path the field strength is much lower than in the focus region, and we have confirmed that any nonlinear processes in the HR-Si wafers such as impact ionization [48] are undetectable. The absolute field strength is calibrated by measuring the phase retardation in the electro-optic sampling and relating this to the field strength via the known electro-optic coefficient of ZnTe.…”

Section: Experimental Setups For Nonlinear Single-pulse and Two-dimensupporting

confidence: 67%

Subcycle Nonlinear Response of Doped 4H Silicon Carbide Revealed by Two-Dimensional Terahertz Spectroscopy

et al. 2019

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We investigate single-cycle terahertz (THz) field-induced nonlinear absorption in doped silicon carbide. We find that the nonlinear response is ultrafast, and we observe up to 20% reduction of transmission of single THz pulses at peak field strengths of 280 kV/cm. We model the field and temperature dependence of the nonlinear response by finite-difference time-domain simulation that incorporates the temporally nonlocal nonlinear conductivity of the silicon carbide. Nonlinear two-dimensional THz spectroscopy reveals that the nonlinear absorption has an ultrafast sub-picosecond recovery time, with contributions from both sumfrequency generation and four-wave mixing, in the form of a photon-echo signal. The ultrafast nonlinearity with its equally fast recovery time makes silicon carbide an interesting candidate material for extremely fast nonlinear THz modulators.

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Section: Experimental Setups For Nonlinear Single-pulse and Two-dimensupporting

confidence: 67%

Subcycle Nonlinear Response of Doped 4H Silicon Carbide Revealed by Two-Dimensional Terahertz Spectroscopy

et al. 2019

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“…A pair of freestanding wire grid polarizers can perform this task as long as the THz signal has its spectral components within the high extinction range of the wire grids, when wavelength is much larger than the wire spacing. As a few examples, wire grid-based attenuation has been used in a range of nonlinear THz studies, using pulses generated by femtosecond tilted pulse front excitation of lithium niobate covering the spectral range up to approximately 2 THz [5,[14][15][16] and femtosecond pumping of organic nonlinear crystals with frequencies up to 5 THz [17]. The main advantage of using a pair of crossed freestanding wire grid polarizers for attenuation is the absence of a substrate, and thus there are no unwanted internal substrate reflections that disturb the signal.…”

Section: Introductionmentioning

confidence: 99%

Attenuation of THz Beams: A “How to” Tutorial

Kaltenecker

Kelleher

Zhou

et al. 2019

J Infrared Milli Terahz Waves

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Attenuation of ultrashort THz pulses poses a significant technological challenge due to the broadband nature of such light pulses. Several methods exist for this purpose, including crossed wire grid polarizers, high refractive index, high resistivity silicon wafers, and ultrathin metal films. In this review, we discuss the operational principles of these methods, and highlight some of the advantages and potential pitfalls of the methods. We describe the limits of high-frequency operation of wire grid polarizers, relevant for contemporary ultra-broadband THz sources in air photonics. We discuss the effects of multiple reflections and interference in sequences of silicon wafers for attenuation, and finally discuss the potential of using ultrathin metallic films for broadband attenuation.

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“…Under this condition, the charge carriers acquire high energies solely because of collisions in the presence of a high-frequency electric field [1,14,15]. Being primarily observed in bulk InSb crystals this effect was further demonstrated for very different three-and two-dimensional semiconductor systems [16][17][18][19][20][21][22][23]. A distinction of the light impact ionization reported in the present work is that it occurs in a system with the Fermi level larger than the forbidden gap.…”

Section: Introductionmentioning

confidence: 99%

High-frequency impact ionization and nonlinearity of photocurrent induced by intense terahertz radiation in HgTe-based quantum well structures

et al. 2019

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We report on a strong nonlinear behavior of the photogalvanics and photoconductivity under excitation of HgTe quantum wells (QWs) by intense terahertz (THz) radiation. The increasing radiation intensity causes an inversion of the sign of the photocurrent and transition to its superlinear dependence on the intensity. The photoconductivity also shows a superlinear raise with the intensity. We show that the observed photoresponse nonlinearities are caused by the band-to-band light impact ionization under conditions of a photon energy less than the forbidden gap. The signature of this kind of impact ionization is that the angular radiation frequency ω = 2πf is much higher than the reciprocal momentum relaxation time. Thus, the impact ionization takes place solely because of collisions in the presence of a high-frequency electric field. The effect has been measured on narrow HgTe/CdTe QWs of 5.7 nm width; the nonlinearity is detected for linearly and circularly polarized THz radiation with different frequencies ranging from f = 0.6 to 1.07 THz and intensities up to hundreds of kW/cm 2 . We demonstrate that the probability of the impact ionization is proportional to the exponential function, exp(−E 2 0 /E 2 ), of the radiation electric field amplitude E and the characteristic field parameter E0. The effect is observable in a wide temperature range from 4.2 to 90 K, with the characteristic field increasing with rising temperature.

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Impact ionization dynamics in silicon by MV/cm THz fields

Cited by 39 publications

References 41 publications

Subcycle Nonlinear Response of Doped 4H Silicon Carbide Revealed by Two-Dimensional Terahertz Spectroscopy

Subcycle Nonlinear Response of Doped 4H Silicon Carbide Revealed by Two-Dimensional Terahertz Spectroscopy

Attenuation of THz Beams: A “How to” Tutorial

High-frequency impact ionization and nonlinearity of photocurrent induced by intense terahertz radiation in HgTe-based quantum well structures

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