A nume rical a pproach that cou ples Loren tz-Drude model incorporated Maxwell equations with Schrödinger equation is pre sented f or the simula tion of pla smonics na nodevices. Maxwell equa tions w ith Lore ntz-Drude (LD ) dispersive model are a pplied to l arge size c omponents, w hereas coupled Maxwell and Schrödinger equations are applied to components where quantum effec ts a re nee ded. The finite difference time do main me thod (F DTD) is appl ied to simulate these cou pled e quations. N umerical re sults of th e coupled ap proach are compared w ith th e conventional approach.