Abstract

In this study, we propose an all optical sensor based on nonlinearity in a multimode interference coupler. The sensor can be tuned to highest sensitivity in the refractive index ranges sufficient to detect protein- based molecules or other water- soluble chemical or biological materials. The nonlinear regimes show the capability to operate on any choice of materials for slab waveguide even conventional glass. The Kerr nonlinear effect is considered as the nonlinear effect for third order nonlinearity materials; this effect is studied in the multimode waveguide with MPA method that promises to investigate the coupler in small lengths. The visible changes of field profile at output facet in various surrounding layer refractive index show the high sensitivity to the refractive index of surrounding layer that is foundation of introducing a sensor. Also, the result show the high distinguished changes on output intensity in various refractive index of surrounding layer even in conventional glass as a chosen material for coupler. To the best of our knowledge this is the first time that a nonlinear MMI in a few micrometers is proposed as a robustness sensor. In fact, this paper brings a useful and powerful way to progress the all optical sensors based on MMI couplers.

© 2013 SPIE