Purcell effect for active tuning of light scattering from semiconductor optical antennas

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Science  15 Dec 2017:
Vol. 358, Issue 6369, pp. 1407-1410
DOI: 10.1126/science.aao5371
  • Fig. 1 Light scattering from Si NWs near a mirror.

    (A) Configuration of the suspended NWs. (B) Light intensity of Newton’s rings (inset) imaged at 500 nm (blue trace), showing that the minimums in the interference pattern (red squares) map the parabolic mirror surface (black dashed line). a.u., arbitrary units. (C and D) Standing wave intensity from an incident (C) and collected (D) TM-polarized plane wave. E, electric field; h, NW height; Ei, incident electric field; ki, incident wave vector; Hi, incident magnetic field, Er, reflected electric field; kr, reflected wave vector; Hr, reflected magnetic field; Embedded Image, dipolar scatterer; Embedded Image, angle of the incident plane wave; Embedded Image, collection angle. (E) Optical images from a single silicon NW at various heights above the mirror shown in (A). Scale bar, 5 μm. (F) Dark-field scattering spectra from three heights shown in (E).

  • Fig. 2 Dipolar modes contributing to light scattering from a Si NW near a mirror.

    (A) Experimental configuration for the results shown in (E) to (H). Embedded Image is the angle of the incident plane wave. (B) The polarization convention for this work. (C and D) Finite-difference time-domain (FDTD) simulation of the total scattering cross section collected at all angles (gray dotted lines), with the electric and magnetic field profiles on resonance (insets) for both polarizations. The experimentally collected scattering spectrum (solid lines) and the corresponding FDTD simulated differential scattering efficiency collected within a 0.7–numerical aperture objective through the quartz handle wafer (black dotted lines). The insets show the field magnitude maps for each resonance labeled as either electric dipole–like (ED) or magnetic dipole–like (MD). Qsca, scattering efficiency; TE, transverse-electric polarization; TM, transverse-magnetic polarization. (E and F) Experimentally collected light scattering spectra at heights ranging from 0 to 2000 nm for TE and TM polarization with a scale of arbitrary units. Dark-field images of the NW vertically scaled to compensate for the parabolic shape of the mirror are shown to the right of each plot. The simulated electric (black) and magnetic (white) field maxima are overlaid, with the width of the lines corresponding to the magnitude of the field maxima. (G and H) Analytic model of far-field diffracted light scattered from a Si NW above an Al mirror for both polarizations, showing the ratio of the intensity of the scattered light (Iff) to the incident intensity (I0) collected normal to the mirror plane where the observation distance is r = 2/(πk).

  • Fig. 3 Active tuning of light scattering with a nanoelectromechanical device.

    (A) Scanning electron micrograph of a fabricated device with a suspended Si NW of ~60 nm in width. Scale bars, 2 μm (main panel); 100 nm (inset) (B) Dark-field scattering image of the device shown in (A). (C) Dark-field scattering spectra confocally collected from the Si NW under applied bias and TM polarization. (D) Dark-field images of the NW at each bias shown in (C). Scale bar, 2 μm. (E) Dark-field scattering shown over time as the bias is turned on and off for 10 cycles at 6-s switching intervals. (F) Modulation in the intensity for selected wavelengths over the 10 switching cycles, showing repeatable and consistent amplitude control for applied biases of 0 and 2.75 V.

Supplementary Materials

  • Purcell effect for active tuning of light scattering from semiconductor optical antennas

    Aaron L. Holsteen, Søren Raza, Pengyu Fan, Pieter G. Kik, Mark L. Brongersma

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    • Materials and Methods 
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