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Volume 16 Issue 6, June 2022

Efficient terahertz free-electron laser

Artistic image of a high-efficiency, single-pass terahertz free-electron laser (THz FEL). Bunches of electrons (small pink spheres) are accelerated inside a tapered helical magnetic undulator (coloured periodic structure) and an inner waveguide with a circular cross-section guides the emitted terahertz radiation. The result is a compact THz FEL with a 10% efficiency of operation at 160 GHz using a 1-m-long undulator.

See Fisher et al. and Yan and Liu

Image: Youna Park, University of California at Los Angeles. Cover Design: Bethany Vukomanovic

Comment

  • A heat-powered emitter can sometimes exceed the Planck thermal-emission limit. We clarify when such super-Planckian emission is possible, arguing that far-field super-Planckian emission requires a distribution of energy that is not consistent with a unique temperature, and therefore the process should not be called ‘thermal emission’.

    • Yuzhe Xiao
    • Matthew Sheldon
    • Mikhail A. Kats
    Comment

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Q&A

  • Nature Photonics spoke to Hillel Adesnik from UC Berkeley about the benefits of using photonic techniques in optogenetics and the key challenges laying ahead.

    • Giampaolo Pitruzzello
    Q&A
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News & Views

  • A single-pass free electron laser operating at 0.16 THz with an energy efficiency of ~10% promises compact and high-power sources in the terahertz spectral region.

    • Lixin Yan
    • Zhuoyuan Liu
    News & Views
  • High-harmonics spectroscopy reveals the closure of the bandgap between adjacent conduction bands in solids driven by high-intensity laser fields, providing insight into light-driven modifications of band structures

    • Dieter Bauer
    News & Views
  • The strongly temperature-dependent band-edge absorption from gallium arsenide enables an optical thermometer with nanokelvin temperature resolution and microscale spatial resolution.

    • Chaman Gupta
    • Peter J. Pauzauskie
    News & Views
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