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ZnO nanostructures are proposed to enhance the performance of surface plasmon resonance (SPR). The ZnO nanostructures on a 50 nm-thick Au thin-film are composed of nano-holes with a period of 300 nm. The ZnO nano-holes coupled SPR was simulated using the three-dimensionanl finite-difference time-domain method. The ZnO nano-holes have been fabricated by a laser interference lithography and wet etching process. The measured resonance angle of 47.5°was obtained; this agreed well with the simulated result. In comparison with the author's previous report, the figure of merit of ZnO nano-holes coupled SPR was two times higher than that of the ZnO grating structure.Introduction: Surface plasmon resonance (SPR) sensors have been extensively studied for chemical and biological sensing applications. Recently, SPR sensors with the ZnO dielectric medium on the metal layer have been focused on biosensors and gas sensors owing to their advantages, such as chemical sensitivity to volatile and other radical gases, high chemical stability, non-toxicity, and low cost [1]. However, the SPR spectrum becomes broader owing to the presence of the ZnO layer, which means the full width half maximum (FWHM) becomes larger. As a result, the efficiency of SPR is degraded, which has affected the resolution and reliability of SPR sensors. In order to achieve reliable and accurate detection of trace amounts, high performance of SPR is essential. Nanostructures can be an attractive SPR sensing platform because they provide strong light confinement and localisation of electric fields even in the case of structures with low refractive index difference [2]. Most studies on the properties of nanostructures coupled SPR reported so far have been based on a one-dimensional nanostructure of grating [3,4]. In this study, a two-dimensional (2D) ZnO nanostructure was suggested to enhance the coupling between localised surface plasmon resonances (LSPs) and propagating surface plasmons (SPs). Then we demonstrated Au/glass SPR structures with arrays of 2D ZnO nano-holes. The SPR characteristics of 2D ZnO nano-holes were calculated using the three-dimensional finite-difference time-domain method (3D-FDTD) method, such as the resonance spectrum and electric field profile. The 2D ZnO nano-holes were realised on the Au layer using a laser interference lithography (LIL) process. The properties of SPR were measured using an attenuated total reflection method, and compared with our previous report [5].

A novel triangular resonator with a long evanescent field around the critical angle has been analysed and demonstrated for the first time. The sensitivity of the resonance shift used for changing the refractive index of 1 × 10 25 at the incidence angle of 188 is 1.04 × 10 27 nm/ RIU for transverse magnetic polarised light. An extinction ratio of 6 dB was observed near 1550 nm, where the incidence angle of the total internal reflection mirror inside the resonator was 188.Introduction: Microring resonators are very desirable for photonic applications owing to their compact features and manifold functionality [1]. Owing to very high Q-factor resonances and steep slopes, photonic microring resonators have begun to be employed in biological and chemical sensing [2]. Triangular resonators, also known as ring resonators, can provide an attractive solution for such functions [3]. Very compact cavities can be achieved by combining the total internal reflection (TIR) mirrors with regular waveguides. One of the TIR mirrors can then be used for the sensing region because of the Goos-Hänchen (GH) effect in the TIR mirror having a sharp incident angle. The TIR mirror having a sharp incident angle increases the evanescent field owing to the GH shift. Because of this, long evanescent fields can be employed to measure the quantities happening in biological events. In this Letter, we propose and investigate a novel triangular ring resonator incorporating a TIR mirror with a long evanescent field to achieve compactness and high sensitivity.