Backside Illumination SPR Generating Structure for Efficient Light Coupling

In this study, a grating structure for efficient backside illumination SPR coupling is proposed for application toward miniaturized SPR sensors. An embedded grating structure with a flat surface which is in contact with the sample was fabricated. The 300-nm-thick SOI top layer was utilized as a fully embeddable grating among a SU-8 substrate employing bulk micromachining. RCWA calculations confirm that the proposed structure exhibit high SPR coupling efficiency and can be applied to the SPR sensor. The experimentally obtained optical response of the fabricated structure confirmed that the SPR efficient coupling is possible. This technology will contribute to making a miniaturized one-chip SPR sensor.