We propose a closed form formulation for the impedance of the metal–insulator–metal (MIM) plasmonic transmission lines by solving the Maxwell’s equations. We provide approximations for thin and thick insulator layers sandwiched between metallic layers. In the case of very thin dielectric layer, the surface waves on both interfaces are strongly coupled resulting in an almost linear dependence of the impedance of the plasmonic transmission line on the thickness of the insulator layer. On the other hand, for very thick insulator layer, the impedance does not vary with the insulator layer thickness due to the weak-coupling/decoupling of the surface waves on each metal–insulator interface. We demonstrate the effectiveness of our proposed formulation using two test scenarios, namely, almost zero reflection in T-junction and reflection from line discontinuity in the design of Bragg reflectors, where we compare our formulation against previously published results.
© 2012 Optical Society of America
Optics at Surfaces
Original Manuscript: November 21, 2011
Manuscript Accepted: February 3, 2012
Published: March 12, 2012
Hamid Nejati and Ahmad Beirami, "Theoretical analysis of the characteristic impedance in metal–insulator–metal plasmonic transmission lines," Opt. Lett. 37, 1050-1052 (2012)