Wall thickness dependent double optical bistability in gold nanotube: A physical mechanism based on local field enhancement

The intrinsic optical bistability (OB) in a two-phase composite, a nonlinear gold nanotube embedded in a linear dielectric host, is investigated by theoretical calculation. Based on quasistatic approximation and Kerr nonlinearity, we obtain the local electric field in a certain position of the gold nanotube as a function of the incident field. In addition to the single OB, the appearance of double OB and optical tristability are also reported. It is shown that both wavelength and wall thickness can dramatically affect the optical bistable behavior of gold nanotube. Both the critical wavelength and the region of double OB decrease obviously with increasing the wall thickness. Thus double OB only appears in the thinner gold tube and is absent as the wall thickness exceeds the critical value. Furthermore, all these OB characteristics have been explained by the local field enhancement effect.