[17a-A402-1~11] 3.12 Nanoscale optical science and near-field optics

[17a-A402-11] Acquisition of optical absorption spectra by gold nanoparticles using an inline/picoliter spectrometer cell fabricated inside a glass optical fiber

〇Masahiko Shiraishi¹, Michiko Nishiyama¹, Kazuhiro Watanabe¹, Shoichi Kubodera¹ (1.Soka Univ.)

Keywords:Localized surface plasmon resonance, Optical fiber sensor, Femtosecond laser processing

We have fabricated a spectrometer cell with a sensing volume of several picoliters by use of a near UV (NUV) femtosecond laser drilling in the middle of a glass optical fiber. By use of the cell with a small sensing volume, spectroscopic measurements using localized surface plasmon resonance (LSPR) were demonstrated. The parameters of the laser system in order to fabricate a micro through-hole inside a glass optical fiber were revealed. The microhole worked as an inline/picoliter spectrometer cell, which had capability of measuring refractive indices of liquid samples by using a combination of a halogen white light source and a compact CCD spectrometer. The spectrometer cell was fabricated into an optical glass fiber by focusing the NUV femtosecond laser pulses at a wavelength of 400 nm with an energy of 30 μJ. The laser beam was focused from two directions opposite to each other to fabricate a micro through-hole spectrometer cell. A diameter of the cell was approximately 3 μm, and the length was approximately 62.5 μm, which was nearly equal to the core diameter of the optical fiber. Absorption spectra using LSPR were obtained with the spectrometer cell. Liquid solution of gold nanoparticles (GNPs) with a diameter of 5 - 10 nm was injected into the spectrometer cell with the volume of 0.4 pL. The absorption peak centered at 518 nm was observed.