Ionization-induced conversion of ultrashort Bessel beam to terahertz pulse

Kostin, V. A.; Vvedenskii, N. V.

doi:10.1364/ol.35.000247

Cited by 48 publications

(21 citation statements)

References 19 publications

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“…There are other, generally less efficient mechanisms for THz generation in gases that employ single-color pumps. Such mechanisms involve ponderomotive effects in a preformed plasma [20], excitation of plasma oscillations [21][22][23] or conical Cherenkov radiation [24][25][26].…”

Section: Introductionmentioning

confidence: 99%

Tailoring terahertz radiation by controlling tunnel photoionization events in gases

et al. 2011

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Applications ranging from nonlinear terahertz spectroscopy to remote sensing require broadband and intense THz radiation which can be generated by focusing two-color laser pulses into a gas. In this setup, THz radiation originates from the buildup of the electron density in sharp steps of attosecond duration due to tunnel ionization, and subsequent acceleration of free electrons in the laser field. We show that the spectral shape of the THz pulses generated by this mechanism is determined by superposition of contributions from individual ionization events. This provides a straightforward analogy with linear diffraction theory, where the ionization events play the role of slits in a grating. This analogy offers simple explanations for recent experimental observations and opens new avenues for THz pulse shaping based on temporal control of the ionization events. We illustrate this novel technique by tailoring the spectral width and position of the resulting radiation using multi-color pump pulses.

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Section: Introductionmentioning

confidence: 99%

Tailoring terahertz radiation by controlling tunnel photoionization events in gases

et al. 2011

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“…In general, the ionizing laser pulse produces a finite residual current density at the ionization front [53][54][55][56][57][58], which should be taken into account in the initial conditions (2.3). This residual current density may arise due to the acceleration of freed carriers by the ponderomotive force of the laser pulse or by the electric field of the fewcycle or bichromatic laser pulse itself.…”

Section: Substitution Ofmentioning

confidence: 99%

Dc to ac field conversion due to leaky-wave excitation in a plasma slab behind an ionization front

Kostin

Vvedenskii

2015

New J. Phys.

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We present a way for generating coherent tunable electromagnetic radiation through dc to ac field conversion by an ionization front. The conversion is caused by the excitation of leaky waves behind the transversely limited ionization front propagating in a uniform electrostatic field. This differs significantly from the well-known dc-to-ac-radiation-converter models which consider Doppler-like frequency conversion by a transversely unlimited ionization front propagating in a spatially periodic electric field. We explore the dispersion properties and excitation of these leaky waves radiated through the transverse plasma boundary at the Cherenkov angle to the direction of propagation of a superluminal ionization front as dependent on the parameters of the plasma produced and on the speed of the ionization front. It is shown that not only the center frequency but also the duration and waveform of the generated pulse may significantly depend on the speed of the ionization front. The results indicate the possibility of using such converters based on planar photoconductive antennas to create sources of microwave and terahertz radiation with controllable waveforms that are transformed from video to radio pulse when the angle of incident ionizing radiation is tuned. laser pulse on a photoconductive material flat boundary [5,6,20,21]. In this case, the speed of the generated ionization front is greater than the speed of light and is determined by the incident angle of the ionizing radiation, which makes it easy to control the front speed through the adjustment of the angle. Available femtosecond laser systems are capable of securing the propagation of such fronts over sufficiently long distances and the formation of subsurface plasma over sufficiently large areas (tens of square centimeters) [24][25][26][27]. Photoconductive devices (including large-area ones) that use ultrafast ionization have been used for generation, detection, frequency conversion, phase shifting, and fast switching of terahertz or microwave radiation (see, e.g., [5][6][7][20][21][22][23][24][25][26][27][28][29][30][31]).Since the speed of propagation of ionization fronts is greater than the speed of light, fast leaky polarization waves are excited behind the front and radiate energy through the transverse plasma boundaries at an angle to the direction of front propagation. Leaky waves have been actively studied for more than half a century (see, e.g., [32][33][34][35][36][37][38][39][40][41][42][43]) and are now attracting attention in the context of the development of emitting and receiving devices with large apertures, including those which use metamaterials and photonic crystals [39][40][41][42][43]. In our case, the excited leaky waves are of a rarely studied type; they have complex values of frequency and wavenumber whose ratio has a real value equal to the speed of the ionization front. Here lies a distinction between our problem and similar ones regarding the conversion of plane waves interacting with an instantly generated plasma slab or half...

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“…[10][11][12][13][14][15][16][17] The residual current is an initial impetus to plasma polarization and excitation of radiating plasma oscillations with THz frequencies in a wide range of gas pressures and laser pulse intensities. 1,2,7,18 The aforementioned phenomenon started to be studied after the publication of experimental work 19 in 2006. Therein, generation of THz waves was observed when an ionizing pulse with a duration of about three field periods and a wavelength of about 0:8 lm was focused in ambient air.…”

Section: Introductionmentioning

confidence: 99%

Analytical description of generation of the residual current density in the plasma produced by a few-cycle laser pulse

Silaev

Vvedenskii

2015

Phys. Plasmas

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When a gas is ionized by a few-cycle laser pulse, some residual current density (RCD) of free electrons remains in the produced plasma after the passage of the laser pulse. This quasi-dc RCD is an initial impetus to plasma polarization and excitation of the plasma oscillations which can radiate terahertz (THz) waves. In this work, the analytical model for calculation of RCD excited by a fewcycle laser pulse is developed for the first time. The dependences of the RCD on the carrierenvelope phase (CEP), wavelength, duration, and intensity of the laser pulse are derived. It is shown that maximum RCD corresponding to optimal CEP increases with the laser pulse wavelength, which indicates the prospects of using mid-infrared few-cycle laser pulses in the schemes of generation of high-power THz pulses. Analytical formulas for optimal pulse intensity and maximum efficiency of excitation of the RCD are obtained. Basing on numerical solution of the 3D time-dependent Schr€ odinger equation for hydrogen atoms, RCD dependence on CEP is calculated in a wide range of wavelengths. High accuracy of analytical formulas is demonstrated at the laser pulse parameters which correspond to the tunneling regime of ionization. V C 2015 AIP Publishing LLC. [http://dx.

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Ionization-induced conversion of ultrashort Bessel beam to terahertz pulse

Abstract: We examine the conical terahertz emission from the superluminous ionization front created in air by an axicon-focused femtosecond laser pulse. We develop the theoretical model that explains the experimental results and predicts new possibilities to control terahertz pulse parameters.

Cited by 48 publications

References 19 publications

Tailoring terahertz radiation by controlling tunnel photoionization events in gases

Tailoring terahertz radiation by controlling tunnel photoionization events in gases

Dc to ac field conversion due to leaky-wave excitation in a plasma slab behind an ionization front

Analytical description of generation of the residual current density in the plasma produced by a few-cycle laser pulse

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