[20a-C304-1~9] 4.1 Plasmonics and Nanophotonics

▼ [20a-C304-5] ZnO: Ga Microdots Arrays for Mid-IR Plasmonic Biosensing Platforms

〇(D)Shuting Ma¹, Ikuya Ando¹, Yuta Shimoda¹, Hidehiko Yoda², Yuya Sato¹, Yuji Teramura³, Hitoshi Tabata¹, Hiroaki Matsui¹ (1.The Univ. of Tokyo, 2.Utsunomiya Univ., 3.AIST)

Keywords:surface lattice resonances, ZnO: Ga microdot arrays, biosensing platforms

Surface plasmon resonances (SPR) when combined with spectroscopy technique is a powerful method for monitoring dynamic biological interactions under label-free and nondestructive detection. Molecular signals can be enhanced through the coupling between the molecular vibrations and SPRs in mid-IR spectral range. Our research group has developed infrared plasmonics based on highly doped oxide semiconductors. In this work, we focused on ZnO: Ga microdot arrays employing surface lattice resonances (SLRs) as a source of mid-infrared SPRs and intended to demonstrate DNA molecules with phosphate related vibrational absorptions at around 1000 cm^-1. We prepared ZnO: Ga arrays with different lattice (D = 4 μm, L = 2 - 9 μm) on CaF₂ substrates by photo-lithography and pulsed laser ablation. The increase in lattice period resulted in a red-shift of resonant peak, indicating that the resonances of the microdot arrays were attributed to far-field coupling between microdots via their scattered radiation fields. Furthermore, we investigated the optical response when the microdot arrays were placed on substrates with different refractive indices. The resonant peaks shifted to lower wavenumbers with increasing the refractive index, clarifying the resonant peaks were derived from electric-fields at interfaces between microdots and substrates. Moreover, we examined the resonant behaviors excited by s-pol. and p-pol. light under changing incident angles using ellipsometry and confirmed the origins of various resonant peaks through theoretical calculations.