Lee, Han, and Kim reply.

In Letter [1], we reported our finding on the physical origin of wide band-gap opening in planar nanostrips, as derived by application of periodic width modulations in the magnetic waveguides. K. Di et al. in their Comment[2], however, argued that the band gap can be reduced remarkably by applying a linear combination of symmetric and antisymmetric fields (see 'A+B' in the inset of Fig. 1(a)). They also insisted that they could find a complete set of magnonic bands based on all of the mode symmetries. However, their work does not constitute grounds for judging our method " wrong " and our conclusions " erroneous ". Moreover, the excitation field alluded to in the Comment is not sufficiently general to obtain the complete set of magnonic band structures, but rather remains specific. The grounds of these conclusions, drawn from our further work, are the following. In Fig.1(b), the superposition of the two blue and red dispersion curves obtained independently from symmetric ('B') and antisymmetric ('A') excitation fields, respectively, agrees with the dispersion (green) curves obtained from the superposition of those two excitation fields ('A+B'). This indicates that the modes excited independently from the symmetric and antisymmetric fields are not coupled. Thus, the change of the position and width of the band gaps in the dispersion curves for consideration of the 'A+B' field is due only to the existence of addition modes driven by the asymmetric field [2]. Consequently, our results driven by the symmetric field ('B') are physically correct. In Fig.1(b), the bands of the antisymmetric modes are located in between the bands of the symmetric modes, which effects a significant band-gap decrease. However, we newly found that, even with respect to both the symmetric and antisymmetric modes, wide band gaps on the order of 10 GHz can be produced simply by changing the periodicity of the width-modulated wave guides, as shown in Fig. 1(c). Our proposed magnonic crystals still offer wide band gaps on the order of 10