17th International Meeting on Chemical Sensors - IMCS 2018 767 Imprinted photonic crystal nanocavity composed of inversely tapered air holes for highly sensitive optical sensor Kenichi Maeno 1 , Shoma Aki 1 , Kazuo Satoh 2 , Shunichi Murakami 2 , Yusuke Sando 2 , Yusuke Kanaoka 2 , Kenji Sueyoshi 1 , Hideaki Hisamoto 1 , Tatsuro Endo 1, 3 * 1 Osaka Prefecture University, Sakai, Osaka 599-8531, Japan., 2 Osaka Research Institute of Industrial Science and Technology(ORIST), Osaka 594-1157, Japan 3 JST PRESTO, Tokyo, Japan *endo@chem.osakafu-u.ac.jp Abstract Polymer-based photonic crystal nanocavity (PCN) composed of tapered and inversely tapered air holes for optical sensing application was successfully fabricated. Polymer-based PCN fabricated by using nanoimprint lithography (NIL) is a promising device for highly-sensitive optical sensor. From the view point of sensing application, the efficiency of light confinement in PCN is a significant factor. However, polymer-based PCN possessed low efficiency caused of low refractive index of polymer material. In this research we found that the shape of air holes composing PCN contributed to the confinement efficiency. We fabricated PCNs composed of cylindrical, tapered, and inversely-tapered air holes by using NIL technique. As an optical measurement result, the inversely tapered one showed the strongest light confinement and two times higher Q value than that of tapered one. Key words: Photonic crystal nanocavity, Optical sensor, Nanoimprint lithography, inverse taper Introduction Photonic crystal nanocavity (PCN) is an optical resonator capable to confine the light of specific wavelength strongly into nanoscale based on Bragg diffraction derived from wavelength- dimensional periodic nanohole array. This optical phenomenon induces strong light-matter interaction within nanoscale and has applied to various applications, such as ultra-small light sources [1], optical manipulation systems [2], and also optical biosensors [3]. For these applications, quality (Q) factor which designates the efficiency of light confinement is a significant parameter. The value of Q factor is defined as Q = o/. Here o and  indicate resonant wavelength and full width of half maximum of resonant spectrum, respectively. We previously reported polymer-based PCN fabricated on metal substrate which can prevent the light leakage to the base substrate, and successfully observed visible light confinement into PCN [4]. However, the Q value was very low, below one hundred, because of the light leakage to air from photonic crystal slab caused by low refractive index of polymer material. Therefore, suppression of this leakage is important point to improve Q value. Here, we focused on the fact that the smaller air hole radius leads the higher average refractive index (nave.) of the slab because of the high occupancy of polymer material. This fact means the nave. value is “locally” controllable by tuning air hole radius along the depth direction (Fig. 1). In this study, we fabricated three types of polymer-based PCNs composed of different shape of air holes, cylindrical, tapered and inversely tapered shapes. Q values were evaluated by spectrometric analysis. Fig. 1. Schematic illustration of nave. controlled by tuning air hole radius along the depth direction. Experimental Ideal Q values (Qideal) of polymer-based PCNs composed of triangle lattice cylindrical, tapered, or inversely tapered air holes were calculated by using simulation analysis (FDTD solutions). The lattice constant was 300 nm, and the air hole radius was 80 nm. In the case of tapered DOI 10.5162/IMCS2018/P2EM.11