Bidirectional Beam Propagation Algorithm

With the development of integration optics, design of wave guide equipments becomes more and more complicated. After the introduction of calculating the mode properties of optical fibers by Feit and Fleck 1977, the beam propagation method at present is the most widely used tool employed in the study of guided wave optics, largely owing to its numerical speed and simplicity. These attractive properties result chiefly from the use of the paraxial approximation which in turn severely limits the formalism, especially for the optic reflection. So, finite difference beam propagation method and bidirectional beam propagation method are studied; a new bidirectional beam propagation method is presented to improve on precision and calculation quantity.Start with analyzing the disabled ability in reflection for finite difference beam propagation method, this thesis labors the traditional bidirectional beam propagation method, pointing out the presentation of back propagation fields and forward propagation fields is based on a square root operator. The square root operator cannot be solved directly, but by using Padésimulation which is very complicated and large calculation quantity, besides, the precision is not well. Many papers point out that the higher the Padérank is, the better the precision is. To solve this problem, the coefficients of the back propagation fields and forward propagation fields are improved, removing the originally square root coefficients for a constant at the denominator, eliminating the variety infection towards the fields calculating. Further more, because there is no need for Padésimulation at denominator, the calculation quantity is reduced.In the end, the new bidirectional beam propagation method is simulated by MATLAB in TE mode using 3-layers plane wave guide. From the result, we can see that the new method is improved much better in showing the beam propagation and back propagation fields and forward propagation accurately. It's important to improve the wave guide simulation software.