In this work, a highly sensitive sensor made of SiN is proposed that can be used in gas or biological sensing, where the choice depends on whether a marker is used or not. The whole sensor is subjected to water cladding. The proposed device is based on a Mach-Zehnder Interferometer (MZI), while the sensing arm is used for sensing the change in the refractive index of the analyte. Both polarizations (TE, TM) are considered in this study, where a higher sensitivity is achieved for the TE-polarized light. The field confinement in the strip waveguide in the sensing region is investigated and verified with a mode solver, whereas the optimum dimensions are obtained using finite difference eigenmode and finite difference time domain solvers. With a sensing arm length of only 180 μm, the proposed sensor achieves a device sensitivity of about 1942 nm/RIU and a figure-of-merit (FOM) as high as 2284 RIU −1 at the wavelength of 1.55 μm. Higher values of FOM can even be attained by employing a longer sensing arm.
In this paper we present a library of photonic components based on silicon nitride on insulator (SiNOI) waveguide platform. SiNOI is CMOS compatible technology hence it offers mass-scale and low-cost fabrication. It also exhibit much lower propagation losses and thermo-optical coefficient when compared to silicon on insulator (SOI) technology. In addition, it is more tolerant to fabrication tolerance and have wide transparency range from visible to mid-infrared. The SiNOI platform consists of a 400 nm thick SiN layer with 4.5 μm buried silicon dioxide oxide and 3 μm oxide cladding. The library includes single mode waveguides, bend waveguides, power dividers (directional couplers and multimode interferometers), strip to slot mode converters and grating couplers. Components for both the near infrared wavelength at λ=1550 nm and the visible wavelength at λ=633nm are included in this library. These components are the building blocks of various photonic devices and systems for different applications such as light detection and ranging (Lidar) and chemical or biological sensing. The components in the library have been designed and optimized using finite difference eigenmode (FDE) and finite difference time domain (FDTD) solvers. The components of this library were fabricated using applied nanotools (ANT) SiN multi-project wafer (MPW) run. In this MPW run electron beam lithography is used for waveguide patterning. The minimum feature size is 120 nm and the minimum feature spacing is 120 nm. Fully-etched devices are created using anisotropic inductively coupled plasma - reactive ion etching (ICP-RIE) process. The components were experimentally characterized and measurement results were obtained.
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