Reflectance-based TiO2 photonic crystal sensors

Reflectance-based photonic crystal (PC) sensors with ALD TiO₂ pillars for sensing materials with different refractive index (RI) are presented here. The relatively high RI, transparency in visible and IR region and chemical stability make TiO₂ a promising material for PC sensors for applications in food or biomedical industry. An IC-compatible fabrication technique called Atomic layer deposition ARrays Defined by Etch-back technique (AARDE) is employed to form the high aspect ratios TiO₂ nanopillar (240 nm radius and 800 nm pitch) arrays. The optical signals are characterized by means of reflectance other than transmittance, resulting in easier coupling and simpler process steps. High sensitivity of 739.7nm per RI unit is obtained in the 1.4 - 1.6 μm wavelength region.