Design of arbitrary modal electric field in planar waveguides

Abstract

The purpose of this study is to propose a method for designing planar waveguides of arbitrary modal electric field distribution. Normally, the authors know or specify a waveguide and they solve for the mode propagation constant which allows them to plot the electric field. A novel and efficient algorithm is proposed here for determining arbitrary refractive index profile planar waveguides with a given desired mode field distribution. This inverse problem is generally solved using complex and variable refractive index profile planar waveguides. The authors present a method for determining the required refractive index profile for both real and imaginary parts. This inverse problem is solved via modelling the waveguide transversely as a transmission line and work inversely from the electric field. They offer example reconstructions of refractive index profiles which are useful for high-power lasers, mode matching between planar and circular waveguides and complex conjugate electric fields. The method also has applications in designing optical fibres for sensors, where one may require specific shape electric field from a waveguide, and also in refractive index profiling instrumentation.