Concepts for a short wavelength rf gun

Kuzikov, S. V.; Shchelkunov, Sergey V.; Vikharev, A. L.

doi:10.1063/1.4975891

Cited by 5 publications

(3 citation statements)

References 9 publications

(11 reference statements)

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“…On the other hand, it is well known that the absorption coefficient of semiconductors is wavelength-dependent, and as such, different wavelengths are absorbed at different depths. For example, Si has an absorption coefficient corresponding to UV light of at least 2–3 orders of magnitude larger compared to visible light, according to the Beer–Lambert law. − As a consequence, for ultrathin layers, most UV light (high-energy photons) is absorbed near the surface while absorption of lower-energy photons is very weak due to the reduced thickness. − GaAs is a class of group III–V semiconductors that have revolutionized optoelectronics devices. , In addition, due to the direct band gap semiconductor with a relatively narrow band gap (1.42 eV), GaAs is an excellent material for near-infrared photodetectors, , while the responsitivity under UV light is typically low. , Similarly to ultrathin Si and perovskite materials discussed above, ultrathin GaAs Films are expected to have comparably low responsitivity in the infrared region. On the other hand, thin GaAs structures are known to be fully depleted of carriers due to surface states and Fermi level pinning .…”

Section: Introductionmentioning

confidence: 99%

High-Performance Flexible GaAs Nanofilm UV Photodetectors

Zhang

Haggrén

et al. 2023

ACS Appl. Nano Mater.

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Flexible ultraviolet (UV) photodetectors have attracted extensive research interest due to their potential applications in personal UV monitoring, UV electronic eye, anti-UV gloves, and other wearable systems. In this study, we present a highly sensitive flexible UV photodetector based on an ultrathin GaAs layer that is produced using a metal−organic chemical vapor deposition method and epitaxial lift-off film transfer technology. Device performance analysis reveals that the photodetectors made of a 50 nm thick GaAs layer have excellent sensitivity to 365 nm light. Specifically, the responsivity, specific detectivity, and external quantum efficiency could reach as high as 99.01 A W −1 , 1.51 × 10 12 Jones, and 3.37 × 10 4 %, respectively, at −2 V bias voltage, which are comparable to many UV photodetectors made from conventional wide band gap semiconductors. Such outstanding UV response properties are related to the very high absorption coefficient for UV light and carrier mobility of an ultrathin GaAs film. Equally importantly, the mechanical flexibility resulting from reducing the film thickness allows the device to maintain its photoelectric properties even after more than 500 bending cycles. The totality of these results suggests that our flexible UV photodetectors have strong potential applications in future wearable devices.

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Section: Introductionmentioning

confidence: 99%

High-Performance Flexible GaAs Nanofilm UV Photodetectors

Zhang

Haggrén

et al. 2023

ACS Appl. Nano Mater.

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“…Naturally, an accelerating structure fed by such pulses should be based on new principles, which would allow propagation of ultra-broadband radiation [2][3][4]. We propose an accelerating structure (Fig.…”

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confidence: 99%

“…Another application for intense single-cycle THz pulses is high-brightness electron sources. It was recently proposed to use ~1 picosecond pulse to stimulate field emission in a high-gradient electron gun and simultaneously to provide preliminary acceleration of the electron bunch up to a relativistic energy [4]. A combined THz and RF field helps to overcome beam brightness reduction due to space-charge effects.…”

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confidence: 99%

Strong terahertz fields: interaction with condensed matter and electron acceleration

et al. 2017

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Recent years witness fast development of the sources of strong single-pulse terahertz radiation, with the record value for terahertz field being about 80 MV/cm [1]. There appeared quite a number of publications where the nonlinear interaction of such strong THz fields with matter was investigated and new effects in intense THz fields were sought for. In this presentation, we will discuss the specific nonlinear properties of graphene in strong electromagnetic fields and propose our approach of using short THz pulses for acceleration of electrons.The first part of the presentation will be devoted to the discussion of the experimental and theoretical results on optical emission from graphene irradiated by a strong (up to 300 kV/cm) short terahertz pulse. The appearance of emission from graphene was observed in experiment in the 350-600 nm spectral range at high THz fields (Fig. 1). We detected the increase of the optical emission by nearly 3 orders of magnitude, while the THz field increased by a factor of 2 only. The spectrum of the optical emission corresponded to Planck's law for the spectral radiance of a black body. We attribute the optical emission to bias-induced spontaneous emission from energetic charge carriers in the graphene. On the basis of the theoretical analysis, we revealed the importance of the dynamic (ballistic) mechanism of electron-hole pair generation induced by an intense terahertz pulse with subsequent spontaneous radiative recombination. In the second part of the presentation we will discuss our results on the generation of the second optical harmonic (SHG) of laser radiation from graphene in the presence of a high power terahertz pulse. We demonstrated essential amplification of SHG under the action of THz field. Polarization characteristics of SHG specific for graphene will be presented together with the dependence of SHG efficiency on optical and THz fields. Detailed theoretical analysis of von Neumann equation allowed us to propose a new mechanism for SHG in graphene under the combined action of optical and THz fields. This mechanism is caused by broadening of the interband resonance due to quasi-particle acceleration by an intense THz field in the process of interband transition. As a result of the "field" interband resonance broadening, the region of electron-hole generation in k-space becomes asymmetric, which leads to the appearance of necessary anisotropy allowing for SHG in the dipole approximation.Intense single-cycle THz pulses produced by rectification of laser radiation are suitable for high gradient acceleration of electrons. Naturally, an accelerating structure fed by such pulses should be based on new principles, which would allow propagation of ultra-broadband radiation [2][3][4]. We propose an accelerating structure (Fig. 2) consisting of a set of waveguides with different adjusted lengths, in which the synchronism of accelerated particles with transversely propagating THz pulse is sustained [3]. A proper mirror shape allows the acceleration of both pre-accelerated parti...

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