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Volume 15 Issue 12, December 2021

Ultrafast germanium photodiodes

Thanks to a special thin-fin design, the cut-off frequency of a germanium-waveguide photodiode has now reached 265 GHz, into the realm of the best performing III–V high-speed devices. The development suggests that cost-effective silicon-compatible technology can now offer exceptional performance for use in optical communications.

See Lischke et al. and Virot

Image: Anna Lina Orsin – Berlin 2021. Cover Design: Bethany Vukomanovic


  • The National Ignition Facility at Lawrence Livermore National Laboratory reported over 1.3 MJ output, representing 70% of both input laser energy and official ‘fusion ignition’. Operations manager, Bruno Van Wonterghem, delves into the optics and what to expect next.

    • David F. P. Pile


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News & Views

  • The three-dimensional images generated by digital holography are usually limited to a single color. A new technique exploiting frequency combs generates holograms with hundreds of colors at once.

    • Chao Dong
    • David Burghoff
    News & Views
  • The demonstration of a germanium-based photodiode with a 3 dB bandwidth of 265 GHz and compatibility with silicon photonics and CMOS fabrication offers a cost-effective route to faster channel data rates for optical communications.

    • Léopold Virot
    News & Views
  • The direct generation of femtosecond pulses from an 8-μm quantum cascade laser could prove transformative for sensing and spectroscopy.

    • Sukhdeep Dhillon
    News & Views
  • For 20 years, nanoscale 3D printing has been based on two-photon absorption, requiring expensive pulsed lasers. Now, via a two-step absorption process, such printing has been demonstrated using a low-cost, low-power continuous-wave laser diode, showing the potential for dramatic cost reductions in 3D nanoprinting.

    • Paul V. Braun
    • Mark L. Brongersma
    News & Views
  • Measurement of the arrival times of annihilation photons in a detector with greater precision is opening the way to new direct forms of tomographic positron emission imaging that do not require back-projection-based reconstruction techniques.

    • Suleman Surti
    • Joel S. Karp
    News & Views
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Review Articles

  • Progress on Landau level lasers—based on external magnetic field splitting of electronic states—is reviewed, with particular attention paid to the potential for tunable terahertz lasers.

    • Erich Gornik
    • Gottfried Strasser
    • Karl Unterrainer
    Review Article
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  • Visible-spectrum silicon nitride thermo-optic phase modulators based on adiabatic micro-ring resonators with a small device footprint and low power consumption, of potential use for applications like augmented-/virtual-reality goggles, quantum information processing circuits and optogenetics, are presented.

    • Guozhen Liang
    • Heqing Huang
    • Nanfang Yu
  • Positron emission imaging without tomographic reconstruction is demonstrated. A Cherenkov radiation detector detects gamma rays produced by positron–electron annihilation. The position of a positron source is determined with a precision of 4.8 mm.

    • Sun Il Kwon
    • Ryosuke Ota
    • Simon R. Cherry
  • Near-transform-limited 630 fs pulses with 4.5 W of peak power are generated by compensating the dispersion of a quantum cascade laser emitting around 8 μm. Their temporal nature is assessed by a new method called asynchronous upconversion sampling.

    • Philipp Täschler
    • Mathieu Bertrand
    • Jérôme Faist
  • By sandwiching a germanium fin between complementary in situ-doped silicon layers, a waveguide-coupled germanium photodiode with a 3-dB bandwidth of 265 GHz, accompanied by high responsivity and low dark current, is realized.

    • S. Lischke
    • A. Peczek
    • L. Zimmermann
    Article Open Access
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Amendments & Corrections

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