The effective permittivities at dielectric interfaces for the 4th-order finite-difference time-domain (FDTD) method using a symplectic integrator propagator are proposed for the two-dimensional (2-D) TM polarization case. For a given accuracy level, the memory resources required by the 4th-order FDTD method with the effective permittivities are reduced by more than an order of magnitude with comparison to the standard FDTD method. The CPU time is also reduced. The permittivities are derived by matching the numerical reflection and transmission at the interface to the exact ones in 3rd-order accuracy. The accurate performance of the proposed method is demonstrated by various numerical examples.© (2002) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.