Finite difference time domain based investigation of the light transmission characteristics of strongly disordered systems mimicking self-organized nanowire arrays

Abstract

In this study, we have investigated the effects of introducing randomness on the transmission characteristics of light in dielectric nanowire arrays. Periodic, correlated weakly disordered, correlated strongly disordered, and uniform random (uncorrelated disordered) systems are studied using finite difference time domain (FDTD) analysis technique. Upon analyzing the origin of transmission gaps in such arrays, it is found that both Bragg and Mie process are involved in the gap formation process. The shrinkage of gap in disordered arrays confirms the involvement of Bragg process and the sustenance of gap in completely random arrays is an indication of the involvement of Mie process. We have also found that transmission gap can be tuned in random arrays similar to the case in periodic arrays by varying nanowire diameter and fill-factor of the arrays. Red-shifting of the gap with an increase in diameter and blue-shifting for an increase in fill-factor is observed in both periodic and random systems. Again, transmission in the passband region is found to decrease for arrays with higher degree of disorder because of increased scattering in such arrays. We have also proposed optimized designs of power splitters and wavelength demultiplexers that are optimized for passband wavelengths (550 nm and 650 nm). We have found that inverse design based optimization technique can be applied on both periodic and random nanowire arrays to get comparable performance by generating customized designs. Thus, our study will advance the field of disorder photonics by creating scopes for employing disordered systems to realize photonic waveguides and integrated circuits.