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Strong sub-terahertz surface waves generated on a metal wire by high-intensity laser pulses.

Tokita S, Sakabe S, Nagashima T, Hashida M, Inoue S - Sci Rep (2015)

Bottom Line: Here, ultrafast field propagation along a metal wire driven by a femtosecond laser pulse with an intensity of 10(18) W/cm(2) is characterized by femtosecond electron deflectometry.From experimental and numerical results, we conclude that the field propagating at the speed of light is a half-cycle transverse-magnetic surface wave excited on the wire and a considerable portion of the kinetic energy of laser-produced fast electrons can be transferred to the sub-surface wave.The peak electric field strength of the surface wave and the pulse duration are estimated to be 200 MV/m and 7 ps, respectively.

View Article: PubMed Central - PubMed

Affiliation: 1] Advanced Research Center for Beam Science, Institute for Chemical Research, Kyoto University, Gokasho, Uji, Kyoto 611-0011, Japan [2] Department of Physics, Graduate School of Science, Kyoto University, Kitashirakawa, Sakyo, Kyoto 606-7501, Japan.

ABSTRACT
Terahertz pulses trapped as surface waves on a wire waveguide can be flexibly transmitted and focused to sub-wavelength dimensions by using, for example, a tapered tip. This is particularly useful for applications that require high-field pulses. However, the generation of strong terahertz surface waves on a wire waveguide remains a challenge. Here, ultrafast field propagation along a metal wire driven by a femtosecond laser pulse with an intensity of 10(18) W/cm(2) is characterized by femtosecond electron deflectometry. From experimental and numerical results, we conclude that the field propagating at the speed of light is a half-cycle transverse-magnetic surface wave excited on the wire and a considerable portion of the kinetic energy of laser-produced fast electrons can be transferred to the sub-surface wave. The peak electric field strength of the surface wave and the pulse duration are estimated to be 200 MV/m and 7 ps, respectively.

No MeSH data available.


Related in: MedlinePlus

Experimental layout for femtosecond electron deflectometry measurement and emission distribution measurement of fast electrons.The wire is moved after each laser irradiation so that a fresh part of the wire surface is used. A lead plate is placed to shield the phosphor screen from fast electrons and X-rays emitted from the laser-irradiated spot. Fast electrons emitted from the laser-irradiated spot in a direction along the wire are detected by stacked imaging plates.
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f1: Experimental layout for femtosecond electron deflectometry measurement and emission distribution measurement of fast electrons.The wire is moved after each laser irradiation so that a fresh part of the wire surface is used. A lead plate is placed to shield the phosphor screen from fast electrons and X-rays emitted from the laser-irradiated spot. Fast electrons emitted from the laser-irradiated spot in a direction along the wire are detected by stacked imaging plates.

Mentions: A schematic of the experimental setup is shown in Fig. 1. Laser pulses are provided by a 150 fs Ti: sapphire laser system. A p-polarized laser pulse with an energy of 70 mJ is focused onto one side of a 0.3 mm diameter tungsten wire at an incidence angle of 55°. The focused beam has a waist of 6 μm × 4 μm in full width at half-maximum (FWHM), resulting in a peak intensity of 1 × 1018 W/cm2. For probing the electric and magnetic fields, a 500 fs electron pulse with an energy of 390 keV is generated by an apparatus for laser acceleration and pulse compression28; the probe pulse is passed near the wire and detected on a phosphor screen with a charge-coupled device camera placed 85 mm from the wire. The distance between the center of the wire and the electron beam axis is yd = 0.5 mm. The origin of the time delay (coincidence of arrival time at the wire of the laser pulse and the probe electron pulse) is determined by a method based on ponderomotive scattering29; the error in determining the delay is at most ±0.5 ps. The experiments are performed in a vacuum chamber with a pressure of 0.1 Pa.


Strong sub-terahertz surface waves generated on a metal wire by high-intensity laser pulses.

Tokita S, Sakabe S, Nagashima T, Hashida M, Inoue S - Sci Rep (2015)

Experimental layout for femtosecond electron deflectometry measurement and emission distribution measurement of fast electrons.The wire is moved after each laser irradiation so that a fresh part of the wire surface is used. A lead plate is placed to shield the phosphor screen from fast electrons and X-rays emitted from the laser-irradiated spot. Fast electrons emitted from the laser-irradiated spot in a direction along the wire are detected by stacked imaging plates.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4317702&req=5

f1: Experimental layout for femtosecond electron deflectometry measurement and emission distribution measurement of fast electrons.The wire is moved after each laser irradiation so that a fresh part of the wire surface is used. A lead plate is placed to shield the phosphor screen from fast electrons and X-rays emitted from the laser-irradiated spot. Fast electrons emitted from the laser-irradiated spot in a direction along the wire are detected by stacked imaging plates.
Mentions: A schematic of the experimental setup is shown in Fig. 1. Laser pulses are provided by a 150 fs Ti: sapphire laser system. A p-polarized laser pulse with an energy of 70 mJ is focused onto one side of a 0.3 mm diameter tungsten wire at an incidence angle of 55°. The focused beam has a waist of 6 μm × 4 μm in full width at half-maximum (FWHM), resulting in a peak intensity of 1 × 1018 W/cm2. For probing the electric and magnetic fields, a 500 fs electron pulse with an energy of 390 keV is generated by an apparatus for laser acceleration and pulse compression28; the probe pulse is passed near the wire and detected on a phosphor screen with a charge-coupled device camera placed 85 mm from the wire. The distance between the center of the wire and the electron beam axis is yd = 0.5 mm. The origin of the time delay (coincidence of arrival time at the wire of the laser pulse and the probe electron pulse) is determined by a method based on ponderomotive scattering29; the error in determining the delay is at most ±0.5 ps. The experiments are performed in a vacuum chamber with a pressure of 0.1 Pa.

Bottom Line: Here, ultrafast field propagation along a metal wire driven by a femtosecond laser pulse with an intensity of 10(18) W/cm(2) is characterized by femtosecond electron deflectometry.From experimental and numerical results, we conclude that the field propagating at the speed of light is a half-cycle transverse-magnetic surface wave excited on the wire and a considerable portion of the kinetic energy of laser-produced fast electrons can be transferred to the sub-surface wave.The peak electric field strength of the surface wave and the pulse duration are estimated to be 200 MV/m and 7 ps, respectively.

View Article: PubMed Central - PubMed

Affiliation: 1] Advanced Research Center for Beam Science, Institute for Chemical Research, Kyoto University, Gokasho, Uji, Kyoto 611-0011, Japan [2] Department of Physics, Graduate School of Science, Kyoto University, Kitashirakawa, Sakyo, Kyoto 606-7501, Japan.

ABSTRACT
Terahertz pulses trapped as surface waves on a wire waveguide can be flexibly transmitted and focused to sub-wavelength dimensions by using, for example, a tapered tip. This is particularly useful for applications that require high-field pulses. However, the generation of strong terahertz surface waves on a wire waveguide remains a challenge. Here, ultrafast field propagation along a metal wire driven by a femtosecond laser pulse with an intensity of 10(18) W/cm(2) is characterized by femtosecond electron deflectometry. From experimental and numerical results, we conclude that the field propagating at the speed of light is a half-cycle transverse-magnetic surface wave excited on the wire and a considerable portion of the kinetic energy of laser-produced fast electrons can be transferred to the sub-surface wave. The peak electric field strength of the surface wave and the pulse duration are estimated to be 200 MV/m and 7 ps, respectively.

No MeSH data available.


Related in: MedlinePlus