RESUMO
In this paper, a single stage solar cell concentrator is designed and discussed. The proposed concentrator consists of refraction prisms and total internal reflection prisms in the inner and outer areas, respectively. In order to compensate for dispersion, all odd zones gather the light onto the -D position, while all even zones gather the light onto the + D position. Finally, the hybrid concentrator achieves optical efficiency of 89.8% for normally incident light without an antireflection coating. An acceptance angle of +/- 0.78 degree at 1 dB loss is achieved without using additional secondary optics. In addition, the fabrication tolerance is also analyzed.
RESUMO
A guided-mode resonance (GMR) filter with wide angular tolerances is experimentally demonstrated as an authentication label illuminated with unpolarized white light. The proposed filter, based on a free-standing silicon nitride membrane suspended on a silicon substrate, is fabricated by using anisotropic wet etching to remove the substrate beneath the silicon nitride layer. Both grating and waveguide structures without a lower cladding layer, i.e., a substrate, are fabricated simultaneously on a silicon nitride membrane. Since the silicon nitride is transparent within the spectra of visible and infrared light, such suspended-membrane-type GMR filters are well suited for applications within the visible spectrum. Moreover, the high refractive index of silicon nitride allows the proposed filters to have strongly modulated gratings and an immunity to high angular deviation. The measured reflection resonance has an angular tolerance up to +/-5 degrees under normal incidence for the wavelength of 629.5 nm.