Abstract-Metal-organic hybrid resonant terahertz absorbers with SU-8 photoresist dielectric layer

Grbovic, Dragoslav and Alves, Fabio and Kearney, Brian and Waxer, Benjamin and Perez, Rolando and Omictin, George (2013) Metal-organic hybrid resonant terahertz absorbers with SU-8 photoresist dielectric layer. Journal of Micro/Nanolithography, MEMS, and MOEMS, 12 (4). Art. No. 041204. ISSN 1932-5150

.http://resolver.caltech.edu/CaltechAUTHORS:20140318-105658578

We report on the characterization of metal-organic hybrid metamaterials for MEMS-based terahertz (THz) thermal sensors and on the characterization of refractive index of SU-8 in the THz band. This type of metamaterial, coupled with the applicability of SU-8 as a structural material, offers possibilities for quick, simple microfabrication of THz imagers. SU-8, a negative photoresist, is a low-cost material that can quickly be spun onto a substrate at a wide range of thicknesses, and then photolithographically patterned into a variety of structures. It is also transparent to THz radiation and thus a suitable choice for a dielectric spacer in metamaterials. We investigated metamaterials consisting of a 0.18 μm Al ground plane and 0.18-μm layer of patterned Al separated by a dielectric spacer of ∼0.5  μm of SU-8. Absorption close to 70% at around 6.1 THz was observed. A model was developed to simulate absorption spectra of several metamaterials, agreeing well with experiments. Matching simulation to measurements was used to determine the refractive index of SU-8 at THz frequencies, extending the known values from 0.1 to 1.6 THz to as far as 10 THz. Finally, Kirchoff’s law for these metamaterials was verified and their use as THz emitters demonstrated with about 0.8  mW/cm^2 output.