Investigation of MEMS bi-material sensors with metamaterial absorbers for THz imaging
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Authors
Alves, Fabio
Grbovic, Dragoslav
Karunasiri, Gamani
Subjects
Terahertz sensor, bi-material, metamaterial absorber
Advisors
Date of Issue
2014
Date
Publisher
SPIE
Language
Abstract
There has been a continued interest in the terahertz (THz) imaging due to penetration and non-ionizing properties. Real- time imaging in this spectral range has been demonstrated using infrared microbolometer technology with external illumination by quantum cascade lasers (QCL). However, to achieve high sensitivity, it is necessary to develop focal plane arrays using enhanced THz-absorbing materials. One attractive option to achieve real time THz imaging is MEMS bi-material sensor with embedded metamaterial absorbers, consisting of a periodic array of metallic squared elements separated from a homogeneous metallic ground plane by a dielectric layer. We have demonstrated that the metamaterial films can be designed using standard MEMS materials such as silicon oxide (SiOx), silicon oxinitrate (SiOxNy) and aluminum (Al), to achieve nearly 100 % resonant absorption matched to the illumination source, while providing structural support, desired thermomechanical properties and access to external optical readout. The metamaterial structure absorbs the incident THz radiation and transfers the heat to bi-material microcantilevers that are connected to the substrate, which acts as a heat sink, via thermal insulating legs. A temperature gradient builds up in the legs, allowing the overall structure to deform proportionally to the absorbed power. The amount of deformation can be probed by measuring the displacement of a laser beam reflected from the sensor’s metallic ground plane. Several sensor configurations have been designed, fabricated and characterized to optimize responsivity, speed of operation and minimize structural residual stress. Measured figures of merit indicate that the THz MEMS sensors have a great potential for real-time imaging.
Type
Article
Description
The article of record as published may be found at http://dx.doi.org/10.1117/12.2049854
Series/Report No
Department
Physics
Organization
Naval Postgraduate School (U.S.)
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NPS Report Number
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Rights
This publication is a work of the U.S. Government as defined in Title 17, United States Code, Section 101. Copyright protection is not available for this work in the United States.