title: Composition methods for four-port couplers in photonic integrated circuitry.
abstract: 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.
authors.affiliation: Department of Mathematics, School of Natural Sciences and Mathematics, The University of Texas at Dallas, Richardson, Texas 75083-0688, USA.
authors.forename: Tiberiu
authors.initials: T
authors.lastname: Constantinescu
authors.forename: Viswanath
authors.initials: V
authors.lastname: Ramakrishna
authors.forename: Nicholas
authors.initials: N
authors.lastname: Spears
authors.forename: L Roberts
authors.initials: LR
authors.lastname: Hunt
authors.forename: Jian
authors.initials: J
authors.lastname: Tong
authors.forename: Issa
authors.initials: I
authors.lastname: Panahi
authors.forename: Govind
authors.initials: G
authors.lastname: Kannan
authors.forename: Duncan L
authors.initials: DL
authors.lastname: MacFarlane
authors.forename: Gary
authors.initials: G
authors.lastname: Evans
authors.forename: Marc P
authors.initials: MP
authors.lastname: Christensen