Evanescent-wave proton postaccelerator driven by intense THz pulse

Pálfalvi, László; Fülöp, J. A.; Tóth, Gy.; Hebling, J.

doi:10.1103/physrevstab.17.031301

Cited by 79 publications

(64 citation statements)

References 27 publications

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“…175 For tens of mJ pulse energy with tens/hundreds of MV/cm peak electric field strength, several interesting potential applications are in sight like acceleration, longitudinal compression, and undulation of relativistic electron buncheswhich can lead to attosecond pulse generation- 176,177 postacceleration and monochromatization of laser-generated proton bunches with potential applications for Hadron therapy. 178 Optical rectification of near infrared ultrashort laser pulses in nonlinear crystals is an effective way for generation of (near) single cycle THz pulses. LN is very suitable for that because of its extremely high second order nonlinear optical coefficient value (168 pm/V) which is 2.5 times larger than that of ZnTe.…”

Section: Thz Generation-a Promising Applicationmentioning

confidence: 99%

Growth, defect structure, and THz application of stoichiometric lithium niobate

Lengyel

Péter

Kovács

et al. 2015

Applied Physics Reviews

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105

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Owing to the extraordinary richness of its physical properties, congruent lithium niobate has attracted multidecade-long interest both for fundamental science and applications. The combination of ferro-, pyro-, and piezoelectric properties with large electro-optic, acousto-optic, and photoelastic coefficients as well as the strong photorefractive and photovoltaic effects offers a great potential for applications in modern optics. To provide powerful optical components in high energy laser applications, tailoring of key material parameters, especially stoichiometry, is required. This paper reviews the state of the art of growing large stoichiometric LiNbO 3 (sLN) crystals, in particular, the defect engineering of pure and doped sLN with emphasis on optical damage resistant (ODR) dopants (e.g., Mg, Zn, In, Sc, Hf, Zr, Sn). The discussion is focused on crystals grown by the high temperature top seeded solution growth (HTTSSG) technique using alkali oxide fluxing agents. Based on high-temperature phase equilibria studies of the Li 2 O-Nb 2 O 5 -X 2 O ternary systems (X ¼ Na, K, Rb, Cs), the impact of alkali homologue additives on the stoichiometry of the lithium niobate phase will be analyzed, together with a summary of the ultraviolet, infrared, and far-infrared absorption spectroscopic methods developed to characterize the composition of the crystals. It will be shown that using HTTSSG from K 2 O containing flux, crystals closest to the stoichiometric composition can be grown characterized by a UV-edge position of at about 302 nm and a single narrow hydroxyl band in the IR with a linewidth of less than 3 cm À1 at 300 K. The threshold concentrations for ODR dopants depend on crystal stoichiometry and the valence of the dopants; Raman spectra, hydroxyl vibration spectra, and Z-scan measurements prove to be useful to distinguish crystals below and above the photorefractive threshold. Crystals just above the threshold are preferred for most nonlinear optical applications apart holography and have the additional advantage to minimize the absorption even in the far-infrared (THz) range. The review also provides a discussion on the progress made in the characterization of non-stoichiometry related intrinsic and extrinsic defect structures in doped LN crystals, with emphasis on ODR-ion-doped and/or closely stoichiometric systems, based on both spectroscopic measurements and theoretical modelling, including the results of first principles quantum mechanical calculations on hydroxyl defects. It will also be shown that new perspective applications, e.g., the generation of high energy THz pulses with energies on the tens-of-mJ scale, are feasible with ODR-doped sLN crystals if optimal conditions, including the contact grating technique, are applied. V C 2015 AIP Publishing LLC.

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Section: Thz Generation-a Promising Applicationmentioning

confidence: 99%

Growth, defect structure, and THz application of stoichiometric lithium niobate

Lengyel

Péter

Kovács

et al. 2015

Applied Physics Reviews

Self Cite

105

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“…These wavelengths make THz radiation with high peak fields uniquely amenable to non-linear spectroscopy [1]- [2], compact particle-acceleration [3][4][5][6],high-harmonic generation [7], molecular alignment [8] etc .…”

Section: Introductionmentioning

confidence: 99%

Theory of terahertz generation by optical rectification using tilted-pulse-fronts

et al. 2015

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Abstract:A model for THz generation by optical rectification using tiltedpulse-fronts is developed. It simultaneously accounts for (i) the spatio-temporal distortions of the optical pump pulse, (ii) the nonlinear coupled interaction of THz and optical radiation in two spatial dimensions (2-D), (iii) self-phase modulation and (iv) stimulated Raman scattering. The model is validated by quantitative agreement with experiments and analytic calculations. We show that the optical pump beam is significantly broadened in the transversemomentum (k x ) domain as a consequence of the spectral broadening caused by THz generation. In the presence of this large frequency and transversemomentum (or angular) spread, group velocity dispersion causes a spatiotemporal break-up of the optical pump pulse which inhibits further THz generation. The implications of these effects on energy scaling and optimization of optical-to-THz conversion efficiency are discussed. This suggests the use of optical pump pulses with elliptical beam profiles for large optical pump energies. It is seen that optimization of the setup is highly dependent on optical pump conditions. Trade-offs of optimizing the optical-to-THz conversion efficiency on the spatial and spectral properties of THz radiation is discussed to guide the development of such sources.

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“…Intense THz pulses hold promise for the development of a new generation of compact particle and x-ray sources [1,2]. Laser-and THz-driven particle accelerators with unprecedented flexibility can be important for free-electron lasers [2,5] and materials science and could revolutionize medical therapy with x-ray, electron, or proton beams [1,2].Single-cycle or nearly single-cycle THz pulses with high energy can be generated by optical rectification of femtosecond laser pulses. The highest so far THz pulse energy reported from such a source, utilizing the novel organic nonlinear material DSTMS, was 0.9 mJ [6].…”

mentioning

confidence: 99%

Highly efficient scalable monolithic semiconductor terahertz pulse source

Fülöp¹,

Polonyi²,

Monoszlai³

et al. 2016

Optica

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Intense pulses at low terahertz (THz) frequencies of 0.1-2 THz are an enabling tool for constructing compact particle accelerators and for strong-field control of matter. Optical rectification in lithium niobate provided sub-mJ THz pulse energies, but it is challenging to increase it further. Semiconductor sources suffered from low efficiency. Here, a semiconductor (ZnTe) THz source is demonstrated, collinearly pumped at an infrared wavelength beyond the three-photon absorption edge and utilizing a contact grating for tilting the pump-pulse front. Suppression of free-carrier absorption at THz frequencies in this way resulted in 0.3% THz generation efficiency, two orders of magnitude higher than reported previously from ZnTe. Scaling the THz energy to the mJ level is possible simply by increasing the pumped area. This unique THz source with excellent focusability, pumped by novel, efficient infrared sources, opens up new perspectives for THz high-field applications. Terahertz (THz) pulses with high energy and field strength are enabling novel applications [1-4], including resonant control over ionic motion, bound and free electrons, as well as nonresonant and strong-field interactions [3]. Intense THz pulses hold promise for the development of a new generation of compact particle and x-ray sources [1,2]. Laser-and THz-driven particle accelerators with unprecedented flexibility can be important for free-electron lasers [2,5] and materials science and could revolutionize medical therapy with x-ray, electron, or proton beams [1,2].Single-cycle or nearly single-cycle THz pulses with high energy can be generated by optical rectification of femtosecond laser pulses. The highest so far THz pulse energy reported from such a source, utilizing the novel organic nonlinear material DSTMS, was 0.9 mJ [6]. The spectrum obtained from organic materials is typically centered in the 2 to 10 THz range, well suited for nonlinear spectroscopic studies. THz sources with lower frequencies are optimally fitted to the requirements of particle acceleration [1,2,7]. The frequency range below 2 THz can be better accessed with another nonlinear material, lithium niobate, utilizing pump pulses with a tilted intensity front for non-collinear phase matching [8]. THz pulses with more than 0.4 mJ energy were generated with 0.77% efficiency using this technique [7]. However, increasing the THz energy further turned out to be very challenging because of the large pulse-front tilt angle (63°) and the associated large angular dispersion of the pump [9,10]. The effect of a strong THz field on the pump pulse, owing to their nonlinear interaction, leads to additional difficulties involving the reduction of the THz generation efficiency [11] and the distortion of the THz beam [12].Semiconductor nonlinear materials have been extensively used to access the low-frequency part of the THz spectrum. The most popular material is ZnTe, where collinear phase matching is possible at the commonly used 0.8 μm pump wavelength of Ti:sapphire lasers. The highest THz pu...

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Evanescent-wave proton postaccelerator driven by intense THz pulse

Cited by 79 publications

References 27 publications

Growth, defect structure, and THz application of stoichiometric lithium niobate

Growth, defect structure, and THz application of stoichiometric lithium niobate

Theory of terahertz generation by optical rectification using tilted-pulse-fronts

Highly efficient scalable monolithic semiconductor terahertz pulse source

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