Toward a terahertz-driven electron gun

Huang, Wei-Chin; Nanni, Emilio A.; Ravi, Koustuban; Hong, Kyung-Han; Fallahi, Arya; Wong, Liang Jie; Keathley, Phillip D.; Zapata, Luis E.; Kärtner, Franz X.

doi:10.1038/srep14899

Cited by 46 publications

(36 citation statements)

References 32 publications

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“…Terahertz (THz) radiation with extremely high peak field is important for many applications such as high harmonic generation [1], spin control [2], molecule alignment [3], time-resolved nonlinear spectroscopy [4], electron acceleration [5][6][7][8] etc. Among various THz generation methods, optical rectification with intra-pulse difference frequency generation is still the most efficient technique [9][10][11][12][13].…”

Section: Introductionmentioning

confidence: 99%

Temperature dependent refractive index and absorption coefficient of congruent lithium niobate crystals in the terahertz range

Zhou

Huang

et al. 2015

Opt. Express

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Optical rectification with tilted pulse fronts in lithium niobate crystals is one of the most promising methods to generate terahertz (THz) radiation. In order to achieve higher optical-to-THz energy efficiency, it is necessary to cryogenically cool the crystal not only to decrease the linear phonon absorption for the generated THz wave but also to lengthen the effective interaction length between infrared pump pulses and THz waves. However, the refractive index of lithium niobate crystal at lower temperature is not the same as that at room temperature, resulting in the necessity to re-optimize or even re-build the tilted pulse front setup. Here, we performed a temperature dependent measurement of refractive index and absorption coefficient on a 6.0 mol% MgO-doped congruent lithium niobate wafer by using a THz time-domain spectrometer (THz-TDS). When the crystal temperature was decreased from 300 K to 50 K, the refractive index of the crystal in the extraordinary polarization decreased from 5.05 to 4.88 at 0.4 THz, resulting in ~1° change for the tilt angle inside the lithium niobate crystal. The angle of incidence on the grating for the tilted pulse front setup at 1030 nm with demagnification factor of −0.5 needs to be changed by 3°. The absorption coefficient decreased by 60% at 0.4 THz. These results are crucial for designing an optimum tilted pulse front setup based on lithium niobate crystals.

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Section: Introductionmentioning

confidence: 99%

Temperature dependent refractive index and absorption coefficient of congruent lithium niobate crystals in the terahertz range

Zhou

Huang

et al. 2015

Opt. Express

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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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“…By tapering a THz wire waveguide into a tip, the THz pulses can be focussed to subwavelength spot-sizes, which further increases the intensity121314151617181920. One interesting application of this is a new class of pulsed electron guns that use the wire tip as an electron emitter with record brightness21. Moreover, the subwavelength focussing of THz pulses provided by tapered wire waveguides greatly improves the spatial resolution of THz experiments121314151617181920.…”

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confidence: 99%

Single-cycle surface plasmon polaritons on a bare metal wire excited by relativistic electrons

et al. 2016

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Terahertz (THz) pulses are applied in areas as diverse as materials science, communication and biosensing. Techniques for subwavelength concentration of THz pulses give access to a rapidly growing range of spatial scales and field intensities. Here we experimentally demonstrate a method to generate intense THz pulses on a metal wire, thereby introducing the possibility of wave-guiding and focussing of the full THz pulse energy to subwavelength spotsizes. This enables endoscopic sensing, single-shot subwavelength THz imaging and study of strongly nonlinear THz phenomena. We generate THz surface plasmon polaritons (SPPs) by launching electron bunches onto the tip of a bare metal wire. Bunches with 160 pC charge and ≈6 ps duration yield SPPs with 6–10 ps duration and 0.4±0.1 MV m−1 electric field strength on a 1.5 mm diameter aluminium wire. These are the most intense SPPs reported on a wire. The SPPs are shown to propagate around a 90° bend.

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Toward a terahertz-driven electron gun

Cited by 46 publications

References 32 publications

Temperature dependent refractive index and absorption coefficient of congruent lithium niobate crystals in the terahertz range

Temperature dependent refractive index and absorption coefficient of congruent lithium niobate crystals in the terahertz range

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

Single-cycle surface plasmon polaritons on a bare metal wire excited by relativistic electrons

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