Confinement of exciton–polaritons using ridge–trench structures filled with fluorescent dye materials was investigated on the basis of geometrical analysis as well as plasmonic behavior analysis. It was found that the photoluminescence intensity of the dye increased significantly in the trench than on the ridge due to geometry confinement. However, with silver layer deposited between the ridge–trench structure on Si substrate and the fluorescence dye, apparent photoluminescence peaks due to surface plasmon resonance centered at 360 nm (3.45 eV) were generated while the photoluminescence peaks of the dye materials centered at 580 nm (2.14 eV) quenched in the trench. Competition of spontaneous emission coupled into external electromagnetic modes and plasmon modes is the cause for the quench in photoluminescence. Our results show a direct energy transfer from low-energy photoluminescence to higher energy photoluminesence in dye materials due to plasmonic resonance effects.