Rauscher, K.K.RauscherLook, J. vanJ. vanLookHarbers, R.R.HarbersErni, D.D.ErniStrasser, P.P.StrasserWueest, R.R.WueestRobin, F.F.RobinBächtold, W.W.Bächtold2022-03-102022-03-102004https://publica.fraunhofer.de/handle/publica/3467242-s2.0-17144405304We have studied tapers that couple light from a conventional ridge waveguide into a planar photonic crystal (PhC) waveguide.Tapering is achieved by changing the PhC waveguide width either in steps or gradually.Lag e .ects in fabrication provide an additional tapering due to the fact that the hole depths scale with the corresponding hole diameter.Our analysis deals with the out-of-plane loss that arises within such taper sections.The PhC consists of a triangular lattice of air holes introduced into an InGaAsP/InP slab structure.For conceptual studies we use the 2D multiple multipole method (MMP)in conjunction with an extended phenomenological model. This model covers the out-of-plane scattering providing a loss parameter and an e .ective index correction for the holes under consideration.This realistic 2D model is retrieved from full-wave 3D FDTD simulations and measurements.en621conference paper