Vol.:(0123456789) Optical and Quantum Electronics (2019) 51:6 https://doi.org/10.1007/s11082-018-1718-3 1 3 Design and analysis of multi‑hexagonal reversible encoder using photonic crystals S. Monisha 1  · D. Saranya 1  · A. Rajesh 1 Received: 8 June 2018 / Accepted: 26 November 2018 © Springer Science+Business Media, LLC, part of Springer Nature 2018 Abstract In this paper, a 4 × 2 reversible encoder with hexagonal lattice has been designed using two-dimensional photonic crystals with non-linear refractive index. In order to demonstrate the working of the encoder, we have used the multi-hexagonal shaped structure arranged in parallel with appropriate inclination to get the desired output. During its functionality as an encoder, more than 98% of the power is coupled at the output port to obtain logic 1 and less than 17.2% of the power is coupled for obtaining logic 0. In addition, during its func- tionality as a reversible encoder, the logic 1 and logic 0 correspond to 97.5% and 15.1%, respectively. The proposed encoder provides an improved contrast ratio of 12.18 dB and 11.5 dB for logical states of 01 and 10, respectively. Keywords Optical reversible encoder · Photonic crystal · Photonic band gap · Photonic integrated circuits 1 Introduction A crystal is a periodic arrangement of atoms, ions or molecules. The arrangement in which these atoms, ions or molecules are to be repeated in space forms a lattice. Like semicon- ductor, photonic crystal exhibits a certain gap known as photonic band gap (PBG), which prevents a certain range of wavelength. Using this photonic bandgap, we can design and construct optical devices using photonic crystals. The basis on the arrangement of ele- ments in the crystal lattice, photonic crystals are classified into one dimensional (1D), two dimensional (2D), and three dimensional (3D) photonic crystals. In one dimensional pho- tonic crystal, the periodicity exhibits in one direction only so the band gap, index state, and bound states all restricted in one direction only. So this one-dimensional photonic crystal finds fewer applications. * A. Rajesh rajeshtechece@gmail.com S. Monisha monisampath@gmail.com D. Saranya anandsaranya2012@gmail.com 1 School of Electronics Engineering, VIT University, Vellore 14, India