Our FOrtran program MOLCAR is well suited for the hybrid analysis of passive or active longitudinally homogeneous dielectric waveguides in integrated optics or in microwave engineering. Transverse to the propagation direction the waveguides can be shaped arbitrary and the waveguides can be composed of layers with lossy materials like metal and dielectric. The generality of MOLCAR allows the analysis of a wide range of different waveguide structures like slab waveguides, rib waveguides, channel waveguides, diffused channel waveguides, waveguide couplers, structures which include metallic layers like TE/TM mode splitters, microstrip lines, coplanar waveguides, elevated coplanar waveguides, slot lines, strip lines and arbitrary combinations of all these waveguides, e.g. diffused channel waveguides or groove guides. The propagation and attenuation constant, the distribution of all field components and the intensity distribution as well as the characteristic impedance can be obtained by using MOLCAR. The program is based on the method of liens which is a semi-analytical method and yields for that reason a high degree of accuracy with less computational effort. The computational window is drastically decreased by using special absorbing boundary conditions. Especially for waveguides with a weak confinement his proves very advantageous and the occurrence of box modes is also avoided.
On technical reasons it is impossible to produce a Y-branch without a truncated wedge. At this truncation reflections and field deformations appear. This leads to unwanted loss. In this paper the losses and reflections are calculated with the MoL-BPM, a beam propagation method based on the Method of Linies.