The optical coupling efficiency of surface plasmon resonance (SPR) based sensors is theoretically investigated from the first principle. Analytical expressions for the instantaneous electric flux lines associated with the TM modes of a three-layer dielectric-metal-dielectric (DMD) waveguide structure are calculated. It is shown that these electric flux lines appear in the form of dis-... https://fitnessgravesyardes.shop/product-category/end-cap-pair/