A two-dimensional photonic crystal for surface temperature reading of miniature systems

A two-dimensional (2D) photonic band gap (PBG) structure was utilized for the temperature mapping of ultra-small structures, such as microelectromechanical systems (MEMS). Optical properties of GaAs were considered in the design of the device since GaAs is nearly transparent and lossless in the chosen infrared region, and also has a reasonably high dielectric constant of 11.4. The structure consists of a triangular lattice of air holes etched into GaAs, with a lattice constant, a, of 0.382-um, including one linear waveguide and three isolated point defects with radii 0.51a, 0.54a, and 0.57a, respectively. The operational principle of the device is based on guiding and selecting the specifically tuned wavelengths through the corresponding point defects. It has been shown that having processed the intensities, obtained from each defect, in accordance with the blackbody radiation characteristics and the transmission properties of the device, the temperature reading of the target in concern can be obtained. Despite many studies concerning guided modes in 2D PBG materials, few sensor applications exist in the literature. Future work on defects, taking advantage of strongly directional behaviour, frequency selectivity and specific polarization, will highlight the much richer possibilities of the PBG technology for novel applications in the fields from optical MEMS to quantum computing.