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

Abstract

Abstract. 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.

Using Homogeneous Equivalent Parameters in Finite Element Models of Curved Metamaterial Structures

“…As it pertains to the shielding from microwave interference, it is the ability to make planar metamaterials that exhibit near 100% absorption at a specific frequency or frequencies that makes them a viable shielding option [4][5][6]. Many different configurations of electromagnetic metamaterials have been fabricated and tested, and some examples are split-ring resonators [7][8][9], circular fishnet designs [10], resistive film arrays [11], and conductive square arrays [12][13][14]. For our research, the latter design was used and consisted of a matrix of copper squares on top of a dielectric layer, backed by a continuous copper ground plane as shown schematically in Fig.…”

Metal-organic hybrid metamaterial THz imaging band translators

“…Due to the nature and configuration of the device, the residual stress causes it to be intrinsically bent, impinging serious difficulties to the readout. On the other hand, organic materials, such as SU-8 negative photoresist have been widely used as a structural material in MEMS [20][21][22] and its properties as a metamaterial in the THz range have been explored [16]. It exhibits several favorable characteristics, the most important of which is the ability for rapid deposition and patterning through photolithography, completely eliminating the need for etching and consequently reducing the intrinsic stress.…”

“…Nearly perfect terahertz absorption, optimized to a particular monochromatic QCL source, can be achieved using metaldielectric metamaterials [14,15] and metal-organic [16]. In this approach, the image of the target is formed on the focal plane array where the temperature increase on individual pixels in the array is proportional to the amount of incoming THz radiation.…”

“…Initially we fabricated metal-dielectric metamaterials using standard MEMS materials (aluminum and silicon dioxide)., for metamaterial absorbers operating in THz range [16] followed by building metal-organic hybrid thermal translators A highly efficient ultra-thin metamaterial structure was developed with low thermal capacitance and high absorption at the frequency tunable to that of a THz illumination source Fig. 3b), while simultaneously serving as a structural layer for sensors and providing access for external optical readout.…”

CNT Conductive Epoxy Composite Metamaterials: Design, Fabrication, and Characterization

“…The metamaterial patterns must be smaller than the wavelength of incident EM radiation. A common metamaterial configuration that has been studied extensively is the conductive square array [ 10 , 15 , 16 , 17 , 18 ]. Figure 1 provides a schematic of this configuration, highlighting the periodic patterned conductive material layer, the dielectric spacer, and the ground plane.…”