RESUMO
Planar photonic integrated circuits based on four-port couplers offer enhanced sophistication and functionality. Each four-port coupler is characterized by sixteen signal coupling coefficients governed by ten energy constraints. The ability to generate the constrained sixteen coupling coefficients is needed in the analysis of the four-port coupler. However, the energy constraint equations are nonlinear and cumbersome to solve directly. We introduce two techniques to reduce these signal coupling coefficients to a set of six free parameters. Hence we can characterize all possible couplers in terms of their sixteen constrained coupling coefficients, or either of two sets of six free parameters. This reduction in parameters has significant ramifications for the design, specification, and empirical characterization of these useful building blocks.
RESUMO
Novel lattice-filter structures consisting of four-directional couplers are introduced, analyzed, and discussed. Four-directional couplers are discussed, and energy-conservation relations in a field-wave application are derived. A thick linear lattice filter is presented and studied as a simple extension to the traditional lattice. A two-dimensional lattice structure is also introduced and studied. Transfer functions are derived and discussed for several examples.
