Control of Laser High-Harmonic Generation with Counterpropagating Light

Voronov, Sergei; Kohl, Ian Thomas; Madsen, J.; Simmons, J.G.; Terry, Nathan B.; Titensor, J.; Wang, Q.; Peatross, Justin

doi:10.1103/physrevlett.87.133902

Cited by 66 publications

(35 citation statements)

References 15 publications

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“…Differently from QPM in periodically-poled nonlinear crystals [13], where the sign of the nonlinear coefficient is periodically flipped so as to always add constructively interfering contributes to the generated field, QPM in HHG has so far been demonstrated by periodically switchingoff harmonic generation during the out-of-phase intervals. Either a modulation of the pump laser intensity in a modulated-diameter, hollow-core, gas-filled waveguide [14,15,16], or the use of a counter-propagating train of pulses [17,18] were used at this purpose. Recently, theoretical studies have predicted the possibility of achieving QPM by periodically modulating the density of the gas medium [19,20], and a proof-of-concept work has shown the coherent buildup of the harmonic field in two separated gas sources [21].…”

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confidence: 99%

Enhancing the yield of high-order harmonics with an array of gas jets

2008

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We report the experimental observation of an enhancement in the yield of high-order harmonics using an array of gas jets as the source medium. By comparing the experimental outcome for jet arrays of different spacings with the predicted harmonic intensity in the case of slit sources of equivalent lengths, we clearly show how the periodic modulation of the gas density can improve the harmonic yield. This behavior may attributed to a quasi-phase-matching effect which increases the length of coherent harmonic build-up during propagation by partially counteracting the dephasing induced by free electrons.PACS numbers: 32.80. Rm,42.65.Ky,32.80.Fb Keywords: Since its discovery in 1987 [1], the phenomenon of highorder harmonic generation (HHG) has become one of the most interesting topics in the field of highly nonlinear processes. Apart from its fundamental physics interest, HHG is now one of the most promising ways to obtain tunable, short-pulse, narrow-band radiation in the vacuum and extreme ultraviolet (VUV and XUV), and in the soft X-ray regions, where other coherent sources are scarcely available. However, the possibility of using high-order harmonics as a table-top VUV-XUV coherent source for applications is strongly connected to the optimization of the brightness of the source over the broadest spectral range.As in many other nonlinear processes, conversion efficiency in HHG depends on the interplay between the single-atom response [2] and the macroscopic response during propagation in the medium [3]. In particular, a constructive interference of the harmonic field emitted from different locations of the source length can only be obtained over the so-called coherence length L c . For media longer than L c , destructive interference soon depletes the generated field and dramatically limits the conversion efficiency. By an appropriate choice of the interaction parameters it is often possible to make the coherence length longer than the medium, thus reaching the so-called phase-matching conditions. However, when phase-matching is not achievable, one can still artificially beat the coherence length limits by properly modulating the interaction parameters along the field propagation direction. Examples of such quasi-phase-matching (QPM) techniques now abound for low-order nonlinear phenomena in structured crystals, and a few examples have been recently demonstrated in HHG. Many different phenomena contribute to limit the coherence length in HHG. Here, the atomic dispersion and the geometric Guoy phase [4,5], are always accompanied by the dispersion connected to free electrons in the partially ionized medium [6,7], and by the characteristic atomic dipole phase [8,9,10,11,12]. Depending on the gas type and density, and on the level of ionization, the coherence length in HHG is usually so short as to pose a serious limit to significant conversion efficiencies. Differently from QPM in periodically-poled nonlinear crystals [13], where the sign of the nonlinear coefficient is periodically flipped so as to always add c...

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confidence: 99%

Enhancing the yield of high-order harmonics with an array of gas jets

2008

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“…Multiple harmonic generation by laser/beam-plasma interaction has been widely investigated [9]- [13]. The generation of harmonics through a nonlinear mechanism driven by bunching at the fundamental has sparked interest as a path toward enhancing and extending the usefulness of an x-ray free-electron laser (FEL) facility.…”

Section: Introductionmentioning

confidence: 99%

Linear and Nonlinear Electron Beam Heating of Magnetized, Motional, and Dusty Plasma

Khalil¹,

Alotaibi²

2016

JMP

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Recent theoretical work on electron beam heating of magneto-active motional Plasma is presented. Power transfer from beam (plasma heating) and generated electric fields for different physical situations of linear and nonlinear beam-plasma interaction, are studied. Based on previous works ) is also considered. Taking into consideration nonlinear process, dust, plasma motion, and beam velocity inhomogeneity, are found to play a crucial role via power absorbed by the beam and the generated electric field in the system.

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“…Another method of QPM is to scramble the phase of the generated harmonics at zones of destructive interference by a counterpropagating pulse or pulse train, that suppresses emission in these regions (see Figure II.21.d, [115,116,65]), and this can induce QPM [88]. The intensity of counterpropagating pulse interfering with the forward-propagating driving pulse has to be only a small fraction of the driving intensity to eliminate emission [65].…”

Section: Counterpropagating Pulse Trainsmentioning

confidence: 99%

“…Using assisting fields of the same wavelength as the driver (λ a = λ 1 ) the induced phase-modulation can be expressed analytically. Two separate contributions of the interference to the harmonic phase can be identified: a direct one caused by the phase-modulation of the driver field, and an indirect contribution, caused by the intensity modulation [115,65], see Appendix C for more details. In the limit of E a E 1 the amplitude of the direct phase-modulation for harmonic q, caused by the driver field's phase-modulation can be expressed as [65]:…”

Section: Iii41 Phase-modulation Caused By Weak Assisting Fieldsmentioning

confidence: 99%

“…This amplitude modulation thus causes an indirect modulation of the harmonic phase. In this case the atomic phase being Both of these factors have been described in [115,65], for the most relevant case, when the phase difference is calculated for two counterpropagating waves, where ϕ 1 = ω 1 t − k 1 z and ϕ a = ω 1 t + k 1 z, giving δ = 2k 1 z.…”

Section: Amplitude Of Harmonic Phase Modulation Due To Laser Field mentioning

confidence: 99%

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Macroscopic study and control of high-order harmonic and attosecond pulse generation in noble gases

Balogh¹

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Control of Laser High-Harmonic Generation with Counterpropagating Light

Cited by 66 publications

References 15 publications

Enhancing the yield of high-order harmonics with an array of gas jets

Enhancing the yield of high-order harmonics with an array of gas jets

Linear and Nonlinear Electron Beam Heating of Magnetized, Motional, and Dusty Plasma

Macroscopic study and control of high-order harmonic and attosecond pulse generation in noble gases

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