Numerical simulation of light propagation through highly-ordered titania nanotube arrays: dimension optimization for improved photoabsorption.

Propagation of electromagnetic waves in the ultraviolet-visible range (300 to 600 nm) through a unique highly-ordered titania nanotube array structure is studied using the computational technique of Finite Difference Time Domain (FDTD). Through numerical simulation the transmittance, reflectance and absorbance of the nanotube-arrays are obtained as a function of tube length and diameter. The nanotube-arrays are found to completely absorb light having wavelengths less than approximately 330 nm. For wavelengths above 380 nm absorption increases as a function of nanotube length, while above 435 nm absorption increases with decreasing pore size. Computational simulations closely match experimental measurements, indicating the suitability of the computational technique for guiding material optimization.