Numerical Simulation of Optical Sensing by the Far Field Pattern Radiated by Periodic Grating Strips Over Silica Buffer on the Silicon Wire Waveguide

Andrei Tsarev; Vittorio M N Passaro

doi:10.3390/s20185306

Numerical Simulation of Optical Sensing by the Far Field Pattern Radiated by Periodic Grating Strips Over Silica Buffer on the Silicon Wire Waveguide

Sensors (Basel). 2020 Sep 16;20(18):5306. doi: 10.3390/s20185306.

Authors

Andrei Tsarev^{1

2}, Vittorio M N Passaro³

Affiliations

¹ Laboratory of Optical Materials and Structures, Rzhanov Institute of Semiconductor Physics, SB RAS, 630090 Novosibirsk, Russia.
² Laboratory of Semiconductor and Dielectric Materials, Physics Department, Novosibirsk State University, 630090 Novosibirsk, Russia.
³ Photonics Research Group, Dipartimento di Ingegneria Elettrica e dell'Informazione, Politecnico di Bari, Via E. Orabona 4, 70125 Bari, Italy.

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.

Keywords: far field pattern; finite difference time domain (FDTD) method; numerical modeling; optical sensors; segmented grating; silicon oxynitride (SiON); silicon wire.

Publication types

Letter