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Photodetection with Active Optical Antennas

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Science  06 May 2011:
Vol. 332, Issue 6030, pp. 702-704
DOI: 10.1126/science.1203056

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  1. Fig. 1

    An optical antenna-diode for photodetection. (A) Band diagram for plasmonically driven internal photoemission over a nanoantenna-semiconductor Schottky barrier (ϕB). (B) Representation of a single Au resonant antenna on an n-type silicon substrate. (C) Scanning electron micrograph of a representative device array prior to ITO coating, imaged at a 65° tilt angle.

  2. Fig. 2

    (A) Experimental photocurrent responsivity for nine different Au antenna lengths: 110, 116, 122, 128, 134, 140, 146, 152, and 158 nm (points). Solid lines: Eq. 2 fit to the data for ϕB = 0.5 eV. All nanoantennas are 50 nm wide and 30 nm thick. (B) Polarization dependence of photocurrent for a 140 nm × 50 nm antenna excited at λ = 1500 nm (green points), exhibiting a cos2 θ angular dependence (gray line). (C) Photocurrent for a representative antenna as a function of input power (green points). (D) Photocurrent spectra extracted from the responsivity spectra (A) (points) fit with Lorentzian curves (solid lines). (E) Corresponding calculated absorption spectra.

  3. Fig. 3

    Sensing the wavelength of incident light. (A) Relative photocurrent amplitudes at fixed wavelengths for the nine resonator lengths in Fig. 2. The color coding of the points is the same as in Fig. 2. Insets: Raw photocurrent images (normalized) for each device array. (B) Calculated absorption amplitudes for devices that are nominally identical to the experimental system.