Compact integrated optical devices using high index contrast waveguides

In this paper, we have demonstrated two mode interference (TMI) coupler using the material SiO₂/SiON having index contrast (Deltan) of 2% and 5% and the corresponding compact beat lengths are observed as ~103 mum and ~50 mum, respectively. The reduction of the beat length with Deltan and the corresponding width of the coupling zone are analyzed and compared with the experimental results. We also analyzed the coupling coefficients for the TMI couplers and the directional couplers (DC) and observed that the coupling coefficient of a DC with small gap (les 0.02 mum) is same to that of a TMI coupler. We have demonstrated a DC with small gap (<1 mum) and Deltan of 2% and the corresponding beat length is ~207 mum. The wavelength multiplexing/demultiplexing using the TMI couplers is also discussed