A Metal-Dielectric Multilayer Film Applied To Enhance The Transmission Of Two Counter-Propagating Lights

Total internal reflection fluorescence microscopy (TIRFM) among several techniques of determining single molecule orientations by fluorescence measurements is a widely used imaging technique that is useful in probing the structure and dynamics of the basal surfaces of cells due to its excellent surface selectivity and ability to suppress background fluorescence. A single-layer metal film is often coated on surface of the coverslip in TIRFM to efficiently excite fluorescence molecules. However, the coated single-layer metal film decreases largely the transmission of emission fluorescence which propagation direction is contrary to that of the excitation light so that the intensity of detected image cannot be substantiality strengthened. In this paper, a metal-dielectric photonic crystal (MDPC) film is structured. The transmission of two counter-propagation lights from the MDPC film is analyzed by using the characteristic matrix method in the film optics. Compared with the single-layer metal thin film, the MDPC film consisted of 4.5 Ag-Si3N4 layers can increase not only the transmission of the excitation light but also the transmission of the emission light. If such a MDPC film is used to practical TIRFMs, the intensity of single-molecule fluorescence image can be markedly enhanced.