Device design using Gaussian beams and ray matrices in planar optics

Gaussian beams and ray matrices can be used to simplify the calculations needed for the design of planar optics devices (such as lasers and filters), including devices using diffraction gratings. It is shown that the ray matrix method can be used even when a diffraction grating is present and that it is equivalent to Fresnel diffraction. A design example for a laser of the MAGIC type is also presented.>