Wave equation solution by a coupled mode multiple reflection series method

In inhomogeneous media, wave equations are nonseparable and numerical techniques are usually employed. This paper presents an efficient and stable eigenmode solution method. The medium is divided into thin layers and the solution within each layer is expanded in terms of modes. The method differs from the usual eigenmode methods in that mode couplings are achieved through an iterative one-way wave multiple reflection series, which requires only matrix-vector multiplications. The solution is computationally simple, has physical interpretation, and remains stable with respect to evanescent waves.