Theoretical Study for the ITO/Si based High Contrast Grating Structure with Focusing Capability and its Fabrication

High contrast grating (HCG) is the structure made up of the sub-wavelength grating of high-index and the surrounding layer of low-index, which reveals high contrast between two materials. Its advantages include high reflectivity over a broad bandwidth, polarization and wavelength selectivity, optical high-Q resonator, and phase modulation. In this work, the HCG structure comprising of indium tin oxide (ITO) and Silicon (Si), for the surrounding layer and the grating layer respectively, was studied. Its theoretical model was established, and transmittance, phase and optical behavior were calculated by rigorous coupled-wave analysis and finite element method. Furthermore, the established structure was fabricated to validate its feasibility. The fabricated structure shows the focusing capability whose length is about 10 μm, and the feasibility of the structure was demonstrated. It is also meaningful that ITO layer can contribute to the fabrication of the HCG structure, leading to enable the structure to be electrical-driven.