Metamaterial films as narrowband terahertz emitters
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Continued progress in terahertz (THz) research has emphasized the need for both improved THz sources and detectors. One approach to generate a narrowband THz radiation is to use metamaterial absorbers as thermal emitters. We present metamaterial based THz emitters consisting of a 100 nm aluminum layer patterned into squares separated from a ground plane of aluminum by a thin layer of silicon oxide (<2 μm) fabricated using standard microfabrication techniques. These metamaterials were designed to emit in one, two, and three different bands of the 4-8 THz range and demonstrate clearly definable separate peaks with bandwidths of approximately 1 THz. Modifying the multiple band configurations can produce relatively broad emission peak if desired. Single band emitters designed for 4.1, 5.4, and 7.8 THz were observed to emit, respectively, 11, 18, and 36 W/m2 at 400 °C in accordance with Kirchhoff's law of thermal radiation. Coating a 4-inch wafer with these materials and heating it to 400 °C would produce an estimated 86, 145, and 280 mW of power, respectively. Additionally, emitted power increased linearly with temperature, as expected from the Planck’s radiation law in the THz spectral region at elevated temperatures. Emissivity of the metamaterial did not change significantly when heated, indicating that the constituent materials did not significantly change their optical or geometric properties.
The article of record as published may be found at http://dx.doi.org/10.1117/12.2005011