Silicon Nitride Interferometers for Optical Sensing with Multi-micron Dimensions

Abstract

Increasing the size of the smallest features of Photonic Integrated Circuits (PICs) to multi-micron dimensions can be advantageous to avoid expensive and complex lithographic steps in the fabrication process. In applications where extremely reduced chip size is not a requirement, the design of devices with multi-micron dimensions is potential interesting to avoid the need for e-beam lithography. Another benefit is that making the dimensions larger reduces the effect of lithographic imperfections such as waveguide surface roughness. However, the benefits do not come without limitations. Coupling the light in and out of the circuit is more challenging since diffraction gratings are not available when designing for such large dimensions. Circuit bends must have a larger radius of curvature and the existence of multimode propagation conditions can have detrimental impact in the performance of several devices, such as interferometers. In this study we perform simulations of the coupling between a lensed multimode optical fiber and a multi-micron a-SiN:H rib waveguide. Light coupling efficiency is analyzed as a function of distance variations using the FDTD method and compared with coupling to a strip waveguide. Moreover, we use numerical simulations to study the performance of a Mach-Zehnder interferometer sensitive to refractive index variations. Both the interferometer, splitters and combiners are designed with multi-micron dimensions.

Optomechanical system for photonic chip characterization

“…Such a sensing operation can be operated by exploiting different physical principles, like the evanescent field sensing principle [ 6 ] or the light induced plasmonic resonance and its surface propagation [ 7 ]. While end-fire optical coupling to the input waveguide is theoretically possible [ 8 ], when the size of the waveguide section is reduced to small values less than 1m 2 , the optical coupling should necessarily rely on a grating structure [ 9 ]. The drawback of the grating assisted light coupling in the wavelength and polarization dependence of the coupling efficiency [ 10 ].…”

Amorphous silicon grating couplers based on random and quadratic variation of the refractive index

“…Photonic devices and circuits find applications in various fields of science, including communications [1], quantum computing [2], neural networks [3], [4] and sensing, including: biosensors [5]- [7], temperature sensors [8] and gas detectors [9]. Amorphous silicon in its hydrogenated form (a-Si:H) and hydrogenated amorphous silicon nitride (a-SiN:H) are suitable materials for photonic components, the former is usually preferred for applications in the near infrared (NIR) [10] and the latter is used in near infrared [11] and visible light [12]- [14]. Hydrogenated amorphous silicon compounds have the advantage of being compatible with CMOS manufacturing technology [12] and with low temperature deposition methods, such as Plasma-Enhanced Chemical Vapor Deposition (PECVD) [15] and Hot-Wire Chemical Vapor Deposition (HWCVD) [16], contributing to a significant reduction in manufacturing costs.…”