Terahertz-Pulse Emission Through Laser Excitation of Surface Plasmons in a Metal Grating

Welsh, G. H.; Hunt, Neil T.; Wynne, Klaas

doi:10.1103/physrevlett.98.026803

Cited by 116 publications

(109 citation statements)

References 18 publications

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“…Electrons emitted through the SP-enhanced photoelectric effect at metal surfaces are much more energetic than in a conventional photoemission process [16][17][18][19]. This phenomenon has been interpreted in terms of ponderomotive acceleration [16] of the electrons since when they are released from the metal, they further experience a vacuum dressed by the inhomogeneous high-frequency longitudinal SP field.…”

Section: Introductionmentioning

confidence: 99%

Quantum-classical model for the surface plasmon enhanced photoemission process at metal surfaces

et al. 2014

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The main purpose of this work is to propose a theoretical description of the surface plasmon polariton stimulated electron emission process at metal surfaces in which the primary electron ejection from the conduction band is treated quantum mechanically in order to go beyond the approximate approaches used up to now to represent this first step. Our theoretical results are well supported by experimental energy spectra obtained for some tens of femtosecond laser pulses impinging on a gold grating target at various intensities in the GW/cm 2 range. The present model which allows us to discuss various features of the surface plasmon photoemission process such as the role of the surface plasmon phase is rather simple and could be applied with slight modifications to study the stimulated photoemission of metallic nanoparticles which has been a subject of growing interest during the past few years.

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Section: Introductionmentioning

confidence: 99%

Quantum-classical model for the surface plasmon enhanced photoemission process at metal surfaces

et al. 2014

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“…In addition, metal thin-film stacks (heterostructures) are well established, simple and cheap to fabricate. Recent works have indeed demonstrated THz emitters based on metal structures 34,35,36,37 . However, the bandwidth did not exceed 3 THz, and THz field amplitudes competitive with those of ZnTe emitters were obtained only in conjunction with amplified laser pulses 36,37 .…”

Section: Introductionmentioning

confidence: 99%

Efficient metallic spintronic emitters of ultrabroadband terahertz radiation

Seifert¹,

Jaiswal²,

Martens³

et al. 2016

Nature Photon

692

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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“…They argued that multiphoton excitation can take place at the structured metal surface under the strong evanescent field of surface plasmons. Ponderomotive acceleration of electrons in this strong field close to the metal surface was considered as the major mechanism for the generation of THz pulses [5,6]. It has to be noted that they observed a third-to fourth-order power dependence in their work and ruled out the possibility of second-order nonlinear optical rectification [5].…”

mentioning

confidence: 99%

“…A 30 nm thick layer of Au was used in their experiments [5]. They argued that multiphoton excitation can take place at the structured metal surface under the strong evanescent field of surface plasmons.…”

mentioning

confidence: 99%

Percolation-enhanced generation of terahertz pulses by optical rectification on ultrathin gold films

Ramakrishnan

Planken

2011

Opt. Lett.

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Emission of pulses of electromagnetic radiation in the terahertz range is observed when ultrathin gold films on glass are illuminated with femtosecond near-IR laser pulses. A distinct maximum is observed in the emitted terahertz amplitude from films of average thickness just above the percolation threshold. Our measurements suggest that the emission is through a second-order nonlinear optical rectification process, enhanced by the excitation of localized surface plasmon hot spots on the percolated metal film.

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Terahertz-Pulse Emission Through Laser Excitation of Surface Plasmons in a Metal Grating

Cited by 116 publications

References 18 publications

Quantum-classical model for the surface plasmon enhanced photoemission process at metal surfaces

Quantum-classical model for the surface plasmon enhanced photoemission process at metal surfaces

Efficient metallic spintronic emitters of ultrabroadband terahertz radiation

Percolation-enhanced generation of terahertz pulses by optical rectification on ultrathin gold films

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