Electrically driven subwavelength optical nanocircuits

Journal name:
Nature Photonics
Volume:
8,
Pages:
244–249
Year published:
DOI:
doi:10.1038/nphoton.2014.2
Received
Accepted
Published online

Abstract

The miniaturization of electronic and photonic device technologies has facilitated information processing and transport at ever-increasing speeds and decreasing power levels. Nanometallics or ‘plasmonics’ has empowered us to break the diffraction limit and open the door to the development of truly nanoscale optical circuits. A logical next step in this development is the realization of compact optical sources capable of electrically driving such nanocircuits. Nanometallic lasers are a possible candidate, but the realization of power-efficient, electrically pumped nanolasers at room temperature is extremely challenging. Here, we explore a plasmonic light-emitting diode as a possible alternative option. We demonstrate that an electrically driven, nano light-emitting diode is capable of directing light emission into a single-mode plasmon waveguide with a cross-sectional area of 0.016λ2 by exploiting the Purcell effect. With this source, electrically driven subwavelength optical nanocircuits for routing, splitting, free-space coupling and directional coupling are realized for the first time.

At a glance

Figures

  1. Subwavelength slot-waveguide-coupled nano-LED platform.
    Figure 1: Subwavelength slot-waveguide-coupled nano-LED platform.

    a, Schematic showing an integrated, electrically driven optical nanocircuit composed of three-dimensional slot-waveguide components, including two ultracompact splitters, a directional coupler and slot antennas. b, SEM image of a fabricated nano-LED coupled to a slot-waveguide-based T-splitter. Red and blue dashed lines indicate the position for the FIB milled cross-sections in c and d. c, The nano-LED, with the quantum well located between the two red arrows. d, A suspended slot waveguide generated by FIB milling and under-etching of the GaAs substrate. e, Mode profile of an 80-nm-wide and 150-nm-tall slot waveguide.

  2. Optical characterization of the nano-LED source.
    Figure 2: Optical characterization of the nano-LED source.

    a, Electroluminescence emission map overlaid on an SEM image of a 2.5-μm-long nano-LED fabricated on an oxidized AlGaAs substrate. A single light output spot is observed in the gap between the p- and n-contacts. b, SEM image and electroluminescence image overlay of a nano-LED coupled to 5 µm slot waveguide. The collected electroluminescence with x-polarized detection shows a scattering spot at the end of the nano-LED-driven slot waveguide, consistent with the behaviour of gap plasmon guiding and outcoupling. c, Electroluminescence intensity spectrum collected from the device shown in a (red line) and the simulation predicted spectrum (black line). The red arrows indicate the positions of the Fabry-Pérot resonance wavelengths determined from the one-dimensional cavity model. The orange arrow indicates the emission from the GaAs barrier.

  3. Slot waveguide-based T-splitter and slot antennas.
    Figure 3: Slot waveguide-based T-splitter and slot antennas.

    a, Optical image of a T-splitter-coupled nano-LED fabricated on a GaAs substrate. The black dashed rectangle outlines the region shown in e and f. b, Simulated electric field intensity for gap plasmon splitting at a T-junction. c, Top view of the simulated electric field intensity for a 320-nm-long, waveguide-fed slot antenna. d, Side view of the simulated electric field intensity for the waveguide-fed slot antenna across the yellow dashed line in c, showing free-space radiation. e, Electroluminescence scattering image with y-polarized detection overlaid on top of the SEM image of the device. f, Electroluminescence scattering image with x-polarized detection overlaid on top of the SEM image of the device.

  4. Slot-waveguide-based directional coupler.
    Figure 4: Slot-waveguide-based directional coupler.

    a, Simulation of the coupling efficiency to each directional coupler output port as a function of the centre-to-centre separation d between two waveguides. Inset: simulated electric field intensity for a directional coupler with d = 160 nm. Gap plasmons are injected from the input port (white arrow), and can be reflected (red arrow), coupled (blue arrow) or transmitted (orange arrow). b, Electroluminescence scattering image with y-polarized detection overlaid on top of the device SEM image, showing emission from the coupled port. c, Electroluminescence scattering image with x-polarization sensitive detection overlaid on the device SEM image, showing no detectable scattering signal from the transmission port.

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Author information

  1. These authors contributed equally to this work

    • Kevin C. Y. Huang &
    • Min-Kyo Seo

Affiliations

  1. Geballe Laboratory for Advanced Materials, Stanford University, McCullough Building, 476 Lomita Mall, Stanford, California 94305-4045, USA

    • Kevin C. Y. Huang,
    • Min-Kyo Seo &
    • Mark L. Brongersma
  2. Department of Electrical Engineering, Stanford University, David Packard Building, 350 Serra Mall, Stanford, California 94305-9505, USA

    • Kevin C. Y. Huang,
    • Tomas Sarmiento,
    • Yijie Huo &
    • James S. Harris
  3. Department of Physics and Institute for the NanoCentury, KAIST, Daejeon 305-701, South Korea

    • Min-Kyo Seo

Contributions

M.-K.S. and M.L.B. conceived the idea. K.C.Y.H. and M.-K.S. designed the structures. Y.H. and T.S. performed the molecular beam epitaxial growth of the quantum-well structure under the supervision of J.S.H. K.C.Y.H. and M.-K.S. performed theoretical calculations and full-eld simulations. K.C.Y.H. and M.-K.S. fabricated and characterized the samples. K.C.Y.H. and M.L.B. wrote the manuscript. M.L.B. supervised the project.

Competing financial interests

The authors declare no competing financial interests.

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