Abstract
This paper presents results of numerical modeling of a modified design of an optical sensor based on segmented periodic silicon oxynitride (SiON) grating evanescently coupled with silicon wire. This segmented grating works as a leaky waveguide, which filters input power from a broadband optical source and radiates it as an outcoming optical beam with both a small wavelength band and a small beam divergence. The radiation angle strongly depends on the refractive index of the grating environment and provides sensor interrogation by measuring the far field pattern in the focal plane of the lens, which is placed near the sensor element. The device concept was verified by direct numerical modeling through the finite difference time domain (FDTD) method and provided moderate intrinsic limit of detection (iLOD) ~ 0.004 RIU with a possible iLOD ~ 0.001 RIU for 10 mm-long structures.
Highlights
Publications on optical sensors cover about 20% [1] of all publications registered by the Web of Science
A lot of optical sensors use wavelength interrogation based on high precision measuring of the shift in resonance wavelength in the photonic structure, and the value depends on the environment of the sensor element [1,2,3,4,5,6,7,8,9,10]
We present the numerical study of the modified variant of the far field pattern optical sensor with the segmented grating
Summary
Publications on optical sensors cover about 20% [1] of all publications registered by the Web of Science. Wavelength interrogation can be accomplished using a tunable laser with a fine linewidth or by launching the optical beam into the waveguide, which contains a broad wavelength spectrum, say, from the super-luminescence diode, and measuring the transmitting signal by the optical spectrum analyzer (OSA) Both these variants provide the possibility to develop advanced optical sensors [1,2,3,4,5,6,7,8,9,10] with the sensitivity depending on the design of the optical element and the spectrum resolution of the tunable laser or the OSA. The idea of this paper is to present the modified sensor design, which has both high sensitivity and moderate iLOD, which is useful for application as the liquid sensor works in water and has a high optical loss in the telecom band
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