Wysin et al1 suggested that the local field enhancement near a metal surface which occurs if surface plasmons are excited in a metal film, can be useful for observing optical bistability arising from the nonlinearity of the Kerr medium. Other geometrical arrangements2 have also been suggested. These studies assume plane waves in the nonlinear medium and use the Fresnel formulae for reflection and refraction from a layered medium but with linear refractive index replaced by the nonlinear refractive index. This assumes that the fields in the medium are homogeneous. However if surface plasmons are excited, then the fields are inhomogeneous and one has the problem of reflection and refraction from an inhomogeneous layered medium. The inhomogeneity is to be determined self consistently. Thus a proper treatment of optical bistability with surface plasmons should use the nonlinear solutions of the wave equation in Kerr medium. This is what we do in this paper.
Atomic vapors are systems well suited for nonlinear optics studies but very few direct measurements of their nonlinear refractive index have been reported. Here we use the
z-scan technique to measure the Kerr coefficient,
n2, for a Cs vapor. Our results are analyzed through a four-level model, and we show that coherence between excited levels as well as cross-population effects contribute to the Kerr nonlinearity.
Abstract We discuss the feasibility of the Kerr effect in negative refractive index materials under magneto cross-coupling and reservoir interaction. The considered medium is a typical three-level atomic system where we derive both the refractive and the gain spectrum. The profiles are analyzed for a weak probe field, and for varying strengths of the strong control field. The considered scheme shows an enhancement of the Kerr nonlinearity which we attribute to the contribution of the electromagnetic components of the fields. For more realistic experimental conditions, we discuss the dependence of the Kerr effect on different thermal bath coupling constants.