Integrated nanoscale thermoelectric converters of infrared and terahertz irradiation

Integrated nanoscale thermoelectric converters of infrared and terahertz irradiation 

Alexei O. Orlov, Gergo P. Szakmany, Gary H. Bernstein, Wolfgang Porod University of Notre Dame, USA 

 Long-wave infrared (LWIR) and THz detectors are in special interest due to the blackbody radiation of objects at room temperature. These detectors can be used for imaging applications such as hidden objects and defects identification and medical diagnostics. The operation principle of the electromagnetic irradiation detectors (TED[GS1] ) are based on the absorption of the electromagnetic energy that is converted to heat, and then the heat is converted to measurable electrical signal. Antenna-coupled devices exploit the wave nature of the IR and THz radiation. The design of the antenna determines the spectral, polarization, and directional properties of the TED. Unlike bolometers that require read-out current for operation thermocouples are active devices with a direct heat-to-electricity transfer function. In antenna-coupled thermocouples, the radiation-induced antenna currents heat the hot junction of the thermocouple that is converted to measurable electrical signals by the Seebeck effect. The thermoelectric converter is either thermally connected to the antenna, or the converter itself is a part of the resonant absorber. The downscaling of such devices enables a very short response time (t < 100 ns), and the ability to fabricate these devices from single-material nano thermocouples with a cross sectional discontinuity reduces the fabrication complexity. Moreover, by combining a thermocouple and a resonant absorber in one element it is possible to fabricate a device with a symmetric, bipolar, polarization-dependent signal with maximal absolute values corresponding to two orthogonal polarizations of the incident irradiation. Experimental results of TEDs, operating at LWIR (10.6mm) and THz (500-600 mm) frequencies, are presented.

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