Off-resonant magnetization dynamics phase-locked to an intense phase-stable terahertz transient

Vicario, C.; Ruchert, Clemens; Ardana-Lamas, Fernando; Derlet, P. M.; Tudu, B.; Lüning, J.; Hauri, Christoph P.

doi:10.1038/nphoton.2013.209

Cited by 178 publications

(139 citation statements)

References 17 publications

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“…Preliminary tests show that driving such large-area trilayers with intense laser pulses easily yields THz pulses with peak fields of several 100 kV cm -1 which exceed those obtained with more strongly pumped large-area ZnTe emitters 50 . Therefore, spintronic THz sources exhibit a high potential for enabling nonlinear-optical studies 51,52 in the difficult-to-access region between 5 and 10 THz. More generally, our results highlight metallic magnetic multilayers as a new and very promising class of high-performance and broadband THz emitters.…”

Section: Resultsmentioning

confidence: 99%

Efficient metallic spintronic emitters of ultrabroadband terahertz radiation

Seifert¹,

Jaiswal²,

Martens³

et al. 2016

Nature Photon

694

802

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Terahertz electromagnetic radiation is extremely useful for numerous applications such as imaging and spectroscopy. Therefore, it is highly desirable to have an efficient table-top emitter covering the 1-to-30-THz window whilst being driven by a low-cost, low-power femtosecond laser oscillator. So far, all solid-state emitters solely exploit physics related to the electron charge and deliver emission spectra with substantial gaps. Here, we take advantage of the electron spin to realize a conceptually new terahertz source which relies on tailored fundamental spintronic and photonic phenomena in magnetic metal multilayers: ultrafast photo-induced spin currents, the inverse spin-Hall effect and a broadband Fabry-Pérot resonance. Guided by an analytical model, such spintronic route offers unique possibilities for systematic optimization. We find that a 5.8-nm-thick W/CoFeB/Pt trilayer generates ultrashort pulses fully covering the 1-to-30-THz range. Our novel source outperforms laser-oscillatordriven emitters such as ZnTe(110) crystals in terms of bandwidth, terahertz-field amplitude, flexibility, scalability and cost. IntroductionThe terahertz (THz) window, loosely defined as the frequency range from 0.3 to 30 THz in the electromagnetic spectrum, is located between the realms of electronics and optics 1,2 . As this region coincides with many fundamental resonances of materials, THz radiation enables very selective spectroscopic insights into all phases of matter with high temporal 3,4 and spatial 5,6,7,8 resolution. Consequently, numerous applications in basic research 3,4 , imaging 5 and quality control 8 have emerged.To fully exploit the potential of THz radiation, energy-efficient and low-cost sources of ultrashort THz pulses are required. Most broadband table-top emitters are driven by femtosecond laser pulses that generate the required THz charge current by appropriately mixing the various optical frequencies 9,10 . Sources made from solids usually consist of semiconducting or insulating structures with naturally or artificially broken inversion symmetry. When the incident photon energy is below the semiconductor band gap, optical rectification causes a charge displacement that follows the intensity envelope of the incident pump pulse 9,10,11,12,13,14,15,16,17 . For above-band-gap excitation, the response is dominated by a photocurrent 18,19,20,21,22,23,24 with a temporally step-like onset and, thus, generally smaller bandwidth than optical rectification 9 . Apart from rare exceptions 14 , however, most semiconductors used are polar 1,2,12,13,15,16,17,21,22 and strongly attenuate THz radiation around optical phonon resonances, thereby preventing emission in the so-called Reststrahlen band located between ~1 and 15 THz.The so far most promising sources covering the full THz window are photocurrents in transient gas plasmas 9,10,25,26,27,28,29 . The downside of this appealing approach is that the underlying ionization process usually requires amplified laser pulses with high threshold energies on the order of 0....

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Section: Resultsmentioning

confidence: 99%

Efficient metallic spintronic emitters of ultrabroadband terahertz radiation

Seifert¹,

Jaiswal²,

Martens³

et al. 2016

Nature Photon

694

802

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“…Recently, the advance of intense THz sources towards E0.1 GV m À 1 field strength enabled first observations of nonlinear light matter interactions [2][3][4][5][6] , the induction of insulator-to-metal transitions 7 and the cause of DNA damage 8 . However, a large range of THz applications, ranging from ultrafast domain switching [9][10][11] to particle acceleration 12 , requires a giant leap in brightness to match the theoretically predicted needs in field strength being on the order of a few GV m À 1 .…”

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confidence: 99%

Demonstration of a low-frequency three-dimensional terahertz bullet with extreme brightness

2015

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The brightness of a light source defines its applicability to nonlinear phenomena in science. Bright low-frequency terahertz (o5 THz) radiation confined to a diffraction-limited spot size is a present hurdle because of the broad bandwidth and long wavelengths associated with terahertz (THz) pulses and because of the lack of THz wavefront correctors. Here using a present-technology system, we employ a wavefront manipulation concept with focusing optimization leading to spatio-temporal confinement of THz energy at its physical limits to the least possible three-dimensional light bullet volume of wavelength-cubic. Our scheme relies on finding the optimum settings of pump wavefront curvature and post generation beam divergence. This leads to a regime of extremely bright PW m À 2 level THz radiation with peak fields up to 8.3 GVm À 1 and 27.7 T surpassing by far any other system. The presented results are foreseen to have a great impact on nonlinear THz applications in different science disciplines.

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“…Up to present, the minuscule nonlinear response of air has limited the exploration of its nonlinear properties to the optical frequency regime owing to the availability of intense near-infrared (nIR) lasers (e.g Ti:sapphire with a carrier frequency 380 THz). From a fundamental science point of view nonlinear excitation of air (and other gases) by pulses with a lower carrier frequency, in the so-called terahertz gap Up to now both the observation of Kerr nonlinearities and molecular alignment in air at THz frequencies was hampered by the technological void of intense sources [3][4][5][6][7][8][9]. Field-free alignment/orientation of molecules is conventionally done by nIR laser technology which allows for preparing the molecules in a…”

Section: Introductionmentioning

confidence: 99%

“…Up to now both the observation of Kerr nonlinearities and molecular alignment in air at THz frequencies was hampered by the technological void of intense sources [3][4][5][6][7][8][9]. Field-free alignment/orientation of molecules is conventionally done by nIR laser technology which allows for preparing the molecules in a 2 preferred angular distribution prior to their interrogation [10,11 and references therein].…”

mentioning

confidence: 99%

Air nonlinear dynamics initiated by ultra-intense lambda-cubic terahertz pulses

Shalaby

Hauri

2015

Applied Physics Letters

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Abstract:We report on the measurement of the instantaneous Kerr nonlinearity and the retarded alignment of air molecules CO 2 , N 2 and O 2 triggered by an intense, lambda-cubic terahertz pulse. The strong-field, impulsive low-frequency excitation (4 THz) leads to field-free alignment dynamics of these molecules thanks to the THz-induced transient dipole moments in the otherwise non-polar molecules. The strong coupling to the terahertz electric transient results in the excitation of coherent long-living rotational states at ambient pressure. Beyond fundamental investigations of nonlinear properties in gases, our results suggest a novel route towards field-free molecular alignment at laser intensity well below the ionization threshold.Air turns into a nonlinear medium for electromagnetic waves under exceptionally strong fields that manifest itself in phenomena like the instantaneous Kerr nonlinearities and retarded molecular alignment [1]. Up to present, the minuscule nonlinear response of air has limited the exploration of its nonlinear properties to the optical frequency regime owing to the availability of intense near-infrared (nIR) lasers (e.g Ti:sapphire with a carrier frequency 380 THz). From a fundamental science point of view nonlinear excitation of air (and other gases) by pulses with a lower carrier frequency, in the so-called terahertz gap Up to now both the observation of Kerr nonlinearities and molecular alignment in air at THz frequencies was hampered by the technological void of intense sources [3][4][5][6][7][8][9]. Field-free alignment/orientation of molecules is conventionally done by nIR laser technology which allows for preparing the molecules in a

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Off-resonant magnetization dynamics phase-locked to an intense phase-stable terahertz transient

Cited by 178 publications

References 17 publications

Efficient metallic spintronic emitters of ultrabroadband terahertz radiation

Efficient metallic spintronic emitters of ultrabroadband terahertz radiation

Demonstration of a low-frequency three-dimensional terahertz bullet with extreme brightness

Air nonlinear dynamics initiated by ultra-intense lambda-cubic terahertz pulses

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