High sensitivity metamaterial based bi-material terahertz sensor

Fabio Alves; Dragoslav Grbovic; Brian Kearney; Gamani Karunasiri

doi:10.1117/12.2005272

27 March 2013 High sensitivity metamaterial based bi-material terahertz sensor

Fabio Alves, Dragoslav Grbovic, Brian Kearney, Gamani Karunasiri

Proceedings Volume 8624, Terahertz, RF, Millimeter, and Submillimeter-Wave Technology and Applications VI; 862411 (2013) https://doi.org/10.1117/12.2005272
Event: SPIE OPTO, 2013, San Francisco, California, United States

Abstract

We report on the fabrication of a microelectromechanical systems (MEMS) based bi-material terahertz (THz) detector integrated with a metamaterial structure to provide high absorption at 3.8 THz. The absorbing element of the sensor was designed with a resonant frequency that matches the quantum cascade laser illumination source, while simultaneously providing structural support, desired thermomechanical properties and optical read-out access. It consists of a periodic array of aluminum squares separated from a homogeneous aluminum (Al) ground plane by a silicon-rich silicon oxide (SiO_x) layer. The absorbing element is connected to two Al/SiO_x microcantilevers (legs), anchored to a silicon substrate, which acts as a heat sink, allowing the sensor to return to its unperturbed position when excitation is terminated. The metamaterial structure absorbs the incident THz radiation and transfers the heat to the legs where the significant difference between thermal expansion coefficients of Al and SiO_x causes the structure to deform proportionally to the absorbed power. The amount of deformation is probed optically by measuring the displacement of a laser beam reflected on the Al ground plane of the metamaterial absorber. Measurement showed that the fabricated absorber has nearly 95% absorption at 3.8 THz. The responsivity and time constant were found to be 1.2 deg/μW and 0.65 s, respectively. The minimum detectable incident power including the readout noise is around 9 nW. The obtained high sensitivity and design flexibility indicate that sensor can be further tuned to achieve the required parameters for real time THz imaging applications.

Citation Download Citation

Fabio Alves, Dragoslav Grbovic, Brian Kearney, and Gamani Karunasiri "High sensitivity metamaterial based bi-material terahertz sensor", Proc. SPIE 8624, Terahertz, RF, Millimeter, and Submillimeter-Wave Technology and Applications VI, 862411 (27 March 2013); https://doi.org/10.1117/12.2005272

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