Investigating the optical bistability of pure spheroidal nanoinclusions in passive and active host matrices

The study examined the effects of the depolarization factor ( L) and the real and imaginary parts of the dielectric function of the host matrix (ε h ) on the local field enhancement factor and optical bistability of pure spheroidal nanoinclusions with both passive and active host matrices. By solving the Laplace equation in the quasi-static limit, we derived expressions for the electric potentials of the pure spheroidal nanoinclusions. We then incorporated L and the Lorentz–Drude model into these expressions to derive the equation for the enhancement factor in the core of the spheroidal nanoinclusions. The results show that, regardless of whether L varies or remains constant, the pure spheroidal nanoinclusions exhibit only one set of enhancement factor peaks, independent of whether the host matrix is passive or active. However, for the same increase in ε h , the enhancement factor intensities of the pure metal spheroidal nanoinclusions are higher when the host matrix is active compared to when it is passive. The number and intensities of the enhancement factor peaks, as well as the optical bistability of the pure spheroidal nanoinclusions, vary significantly depending on whether the core is made of a passive or active dielectric material. Furthermore, by adjusting parameters such as L and the real and imaginary parts of the host matrices, we were able to achieve tunable enhancement factors and optical bistability, which could be useful for applications in optical sensing, nonlinear optics, and quantum optics.