15:00 〜 15:15
▲ [14p-B409-7] Sensitivity Enhancement in Guided-Mode-Resonance Optical Biosensors via Low Refractive Index Buffer Layer
キーワード：Guided-mode-resonance, Optical biosensor, Low refractive index buffer layer
Guided-mode-resonance (GMR) optical biosensors have attracted great attention for rapid and sensitive chemical analysis and biomedical detection [1-3]. The sensitivity of GMR biosensors is highly related to the distribution of evanescence wave in the waveguide. In this paper, we present a study of enhancing the sensitivity of GMR biosensors by manipulating the evanescent wave distribution using a low refractive index (RI) layer.
Fig. 1. (a) Schematic diagram of GMR biosensors with a low-index SiO2 layer. (b) Calculated sensitivity as a function of the SiO2 and TiO2 layer thicknesses.
Fig. 1(a) shows a schematic diagram of the GMR biosensor. The bio-chip consists of (1) injection-molded cyclic olefin copolymer (COC) substrate (n~1.56) with a 1D grating structure, (2) a low-index SiO2 (n~1.45) buffer layer, (3) and a high-index TiO2 (n~2.17) waveguide layer. The height and period of the grating structure are 100 nm and 417 nm, respectively. Finite-element-method simulations are performed to calculate the GMR wavelength in term of the thicknesses of the SiO2 and TiO2 layers, from which the sensitivity is obtained. The results are depicted in Fig. 1(b). As the thickness of TiO2 layer increases, the sensitivity first increases, and then decreases as the thickness of TiO2 layer increases is greater than 125 nm. On the other hand, as the thickness of the SiO2 layer increases, the sensitivity decreases first, and then increases. This observation is attributed to the introduction of the low-index SiO2 layer that modifies the evanescent wave distribution, then affects the sensitivity of GMR biosensors. These results show that low-index SiO2 layer can be used to enhance the sensitivity of GMR biosensors.
Fig. 1. (a) Schematic diagram of GMR biosensors with a low-index SiO2 layer. (b) Calculated sensitivity as a function of the SiO2 and TiO2 layer thicknesses.
Fig. 1(a) shows a schematic diagram of the GMR biosensor. The bio-chip consists of (1) injection-molded cyclic olefin copolymer (COC) substrate (n~1.56) with a 1D grating structure, (2) a low-index SiO2 (n~1.45) buffer layer, (3) and a high-index TiO2 (n~2.17) waveguide layer. The height and period of the grating structure are 100 nm and 417 nm, respectively. Finite-element-method simulations are performed to calculate the GMR wavelength in term of the thicknesses of the SiO2 and TiO2 layers, from which the sensitivity is obtained. The results are depicted in Fig. 1(b). As the thickness of TiO2 layer increases, the sensitivity first increases, and then decreases as the thickness of TiO2 layer increases is greater than 125 nm. On the other hand, as the thickness of the SiO2 layer increases, the sensitivity decreases first, and then increases. This observation is attributed to the introduction of the low-index SiO2 layer that modifies the evanescent wave distribution, then affects the sensitivity of GMR biosensors. These results show that low-index SiO2 layer can be used to enhance the sensitivity of GMR biosensors.