期刊
NANO LETTERS
卷 16, 期 6, 页码 3801-3808出版社
AMER CHEMICAL SOC
DOI: 10.1021/acs.nanolett.6b01198
关键词
Metafilm; Mie resonance; germanium nanobeam; semiconductor nanoantenna; light absorption
类别
资金
- Light-Material Interactions in Energy Conversion Energy Frontier Research Center - U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences [DE-SC0001293]
- AFOSR [FA9550-14-1-0117]
In 1934, Wilhelm Woltersdorff demonstrated that the absorption of light in an ultrathin, freestanding film is fundamentally limited to 50%. He concluded that reaching this limit would require a film with a real-valued sheet resistance that is exactly equal to R = eta/2 approximate to 188.5 Omega/square, where eta =root mu(0)/epsilon(0) is the impedance of free space. This condition can be closely approximated over a wide frequency range in metals that feature a large imaginary relative permittivity epsilon(r)'', that is, a real-valued conductivity sigma = epsilon(0)epsilon(r)''omega. A thin, continuous sheet of semiconductor material does not facilitate such strong absorption as its complex-valued permittivity with both large real and imaginary components preclude effective impedance matching. In this work, we show how a semiconductor metafilm constructed from optically resonant semiconductor nanostructures can be created whose optical response mimics. that of a metallic sheet. For this reason; the fundamental absorption limit mentioned above can also be reached with semiconductor materials, opening up new opportunities for the design of ultrathin optoelectronic and light harvesting devices.
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