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Impacts of higher-order dispersions and saturable nonlinearities on modulation instability in negative-refractive metamaterials

On the basis of the standard linear stability analysis and Drude electromagnetic model, the impacts of higher-order dispersions and three kinds of typical saturable nonlinearities on modulation instability (MI) have been analyzed and calculated for negative-refractive metamaterials (MMs). Our results show that the MI gain spectra consist of only one spectral region instead of one or two regions in ordinary materials, which may be close to or far from the zero point. Particularly, the spectrum far from the zero point has a high cut-off frequency but a narrow spectral width, which is obviously beneficial to the generation of high-repetition-rate pulse trains. Moreover, MI characteristics here will vary with the normalized angular frequency which can be modified by adjusting the structures of negative-refractive MMs, signifying the controllability of bistable solitons and MI based applications. The effects of saturable nonlinearities are similar to those in ordinary materials.