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[资源] 光学整流天线把光直接变成直流电

An optical rectenna—a device that directly converts free-propagating
electromagnetic waves at optical frequencies to
direct current—was first proposed over 40 years ago1, yet
this concept has not been demonstrated experimentally due
to fabrication challenges at the nanoscale2,3. Realizing an
optical rectenna requires that an antenna be coupled to a
diode that operates on the order of 1 PHz (switching speed
on the order of 1 fs). Diodes operating at these frequencies
are feasible if their capacitance is on the order of a few attofarads3,4,
but they remain extremely difficult to fabricate and
to reliably couple to a nanoscale antenna2. Here we demonstrate
an optical rectenna by engineering metal–insulator–metal
tunnel diodes, with a junction capacitance of ∼2 aF, at the tip
of vertically aligned multiwalled carbon nanotubes (∼10 nm in
diameter), which act as the antenna5,6. Upon irradiation with
visible and infrared light, we measure a d.c. open-circuit
voltage and a short-circuit current that appear to be due to a
rectification process (we account for a very small but quantifiable
contribution from thermal effects). In contrast to recent reports
of photodetection based on hot electron decay in a plasmonic
nanoscale antenna7,8, a coherent optical antenna field appears
to be rectified directly in our devices, consistent with rectenna
theory4,9,10. Finally, power rectification is observed under
simulated solar illumination, and there is no detectable change
in diode performance after numerous current–voltage scans
between 5 and 77 °C, indicating a potential for robust operation.

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