Beyond the perturbative description of the nonlinear optical response of low-index materials

Abstract

We show that standard approximations in nonlinear optics are violated for situations involving a small value of the linear refractive index. Consequently, the conventional equation for the intensity-dependent refractive index, $n(I)=n_0+n_{2}I$, becomes inapplicable in epsilon-near-zero and low-index media, even in the presence of only third-order effects. For the particular case of indium tin oxide, we find that the ${\chi }^{(3)}$, ${\chi }^{(5)}$ and ${\chi }^{(7)}$ contributions to refraction eclipse the linear term; thus, the nonlinear response can no longer be interpreted as a perturbation in these materials. Although the response is non-perturbative, we find no evidence that the power series expansion of the material polarization diverges.

4 pages, 3 figures

References in corpus (2)

• Monolithic CMOS-compatible zero-index metamaterials
• On-chip all-dielectric fabrication-tolerant zero-index metamaterials

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