Materials, Photonic Devices, and Sensors

Silicon nitride directional coupler interferometer for surface sensing

[+] Author Affiliations
Kyohei Okubo, Ken Uchiyamada, Kiyoshi Asakawa, Hiroaki Suzuki

University of Tsukuba, Graduate School of Pure and Applied Sciences, 1-1-1 Tennoudai, Tsukuba, Ibaraki 305-8573, Japan

Opt. Eng. 56(1), 017101 (Jan 05, 2017). doi:10.1117/1.OE.56.1.017101
History: Received August 9, 2016; Accepted December 12, 2016
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Abstract.  A silicon nitride directional coupler (DC) used to create a biosensing device is presented. The DC detects changes in the refractive index of the cladding (nclad) as changes in the relative output intensity. The DC length (L), nclad-dependent sensitivities of the DC, and preferred dimensions of the single-mode DC waveguides are obtained through numerical simulations. The performance of the DC is evaluated through end-fire coupling measurements. The intensities measured after varying the nclad using air, water, and glycerol solutions agree well with the fitting for a wide range of L values between 60 and 600  μm, i.e., corresponding to 6 to 60 times the coupling length. The bulk refractive index sensitivity was investigated using glycerol solutions of different concentrations and was found to be 18.9 optical intensity units per refractive index unit (OIU/RIU). Biotin/streptavidin bindings were detected with a sensitivity of 60 OIU/RIU and a detection limit of 0.13  μM, suggesting the feasibility of the DC for immunosensing.

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© 2017 Society of Photo-Optical Instrumentation Engineers

Citation

Kyohei Okubo ; Ken Uchiyamada ; Kiyoshi Asakawa and Hiroaki Suzuki
"Silicon nitride directional coupler interferometer for surface sensing", Opt. Eng. 56(1), 017101 (Jan 05, 2017). ; http://dx.doi.org/10.1117/1.OE.56.1.017101


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