Mode Conversion/Splitting in Multimode Waveguides Based on Invariant Engineering

We discuss mode conversion and splitting in multimode waveguides based on Lewis-Riesenfeld invariant theory. The design of mode converters/splitters using the dynamical invariant is discussed. Closed form expressions for the modal power at the output for converter/splitter design are derived. Various design approaches are discussed and assessed by beam propagation simulations. We show that the invariant-based engineering scheme reduces device length as compared to the common adiabatic scheme.