Three dimensional two point ray tracing using paraxial rays in cartessian coordinates

Paraxial rays are used for 3D two point ray tracing in complex structures. In this work we use dynamic ray tracing which is formulated in cartessian coordinates. This formulation allows for more flexibility in perturbing the initial slowness and takeoff point of the rays, as compared to the more common dynamic ray tracing in ray centered coordinates. Furthermore, the paraxial rays are adjusted iteratively to conform to the surface and interface topography, and to have slowness vectors with the correct length. This extends considerably the range of validity of the paraxial approximation. We describe implementation of different types of two point ray tracing which include CRP ray tracing, normal incidence ray tracing and CMP ray tracing.