Second-harmonic generation. Consider the process of second-harmonic generation both with ?k = 0 and ?k = 0 in a lossless material. State the conditions under which the following types of behavior occur: (i) The fundamental and second-harmonic fields periodically exchange energy. (ii) The second-harmonic field asymptotically acquires all of the energy. (iii) The fundamental field asymptotically acquires all of the energy. (iv) Part of the energy resides in each component, and this fraction does not vary with z.