Material dependence of the distributed bolometric effect in resonant metallic nanostructures

Optical antennas and passive resonant structures, as frequency selective surfaces, configure a new kind of optical systems that can be classified as belonging to the resonant optics area. Typical antenna-coupled detectors using microbolometers as transducers have included materials with the largest temperature coefficient of resistance (TCR) value. These materials are located at the feed point of the antenna where the electric current is the largest and the Joule effect dissipates the best. At the same time, the signal delivered to the external circuit is also depending on the resistivity value. This two-material configuration requires al least two e-beam fabrication steps. Although the resistivity values of metals changes substantially, the actual range of TCR values for most of metals is quite narrow. In this contribution we analyze how the choice of the material involved in the fabrication of resonant structures may enhance the bolometric effect. This analysis is made taking into account the electromagnetic interaction of light with the resonant element. The generated heat changes temperature and this variation produces the signal. Finite element package Comsol has been used to properly simulate the situation and predict the effect of changing the fabrication to an unique material, simplifying the manufacturing. Besides, the performance of the structure is depending on the used material.