Photonic devices based on stacked multilayer waveguides are widely used in optical integrated architectures like polarizers, filters, photodetectors, laser, transducers for sensing applications, and microelectromechanical systems. In this paper, we present an accurate modeling of a waveguide polarizer based on an antiresonant reflecting optical waveguide (ARROW) structure utilizing birefringence form. The ARROW polarizer is the case of a structure with severe "aspect-ratio" that most of numerical technique cannot handle. The electromagnetic analysis is performed by means of a transmission-line matrix integral-equation (TLMIE) method-based solver. TLMIE is a three-dimensional full-wave hybrid technique that combines the advantages of the numerical transmission-line matrix method in dense finite regions and those of the integral-equation method in homogeneous regions where analytical and/or numerical Green's functions are available. An accurate investigation of propagation/radiation properties of TE/TM modes is performed. Theoretical results of TE/TM losses are compared to measured data showing very good agreement. Starting from this validation, it seems possible to provide design criteria for the optimization of the polarizer.