Title: Spin Wave Optics

Abstract: Similarity between Walker and Helmholtz equations encouraged many to search for analogies between optical and spin wave phenomena. In the present article we demonstrate that one to one relationship can be established by formalizing the concept of magnetic refractive index and deriving on its basis Eikonal equations for magnetic media, formally proving that a very substantial portion of optical devices: lenses, mirrors, waveguides and so on, can be implemented as magnetic devices operating on spin waves instead of optical radiation. Controlling the refractive index is accomplished by changing the environmental variables such as magnetic bias field or temperature. Functionality of the above mentioned devices is confirmed with micromagnetic simulations, which also demonstrate a substantial agreement with the analytical model introduced in the present manuscript.