Silicon nitride waveguide devices based on gradient-index lenses implemented by subwavelength silicon grating metamaterials

Abstract

The rapid development of photonic integrated circuits demands the design of efficient and compact waveguide devices such as waveguide tapers and crossings. Some components in the silicon nitride (SiN) waveguide platform are superior to their counterparts in the silicon waveguide platform. Designing a compact SiN waveguide taper and crossing is crucial to reduce the size of SiN photonic components. In this paper, we utilize the focusing property of the Luneburg lens to design an SiN taper connecting a 10-µm-wide waveguide to a 1-µm-wide waveguide. Three-dimensional full-wave simulations indicate that the designed 13-µm-long taper has an average transmission efficiency of 92% in the wavelength range of 1500–1600 nm. We also present an in-plane SiN waveguide crossing based on the imaging property of the square Maxwell’s fisheye lens designed with quasi-conformal transformation optics. The designed waveguide crossing occupies a compact footprint of 5.65 µ m × 5.65 µ m , while its average insertion loss is 0.46 dB in the bandwidth of 1500–1600 nm. To the best our knowledge, the designed SiN waveguide taper and crossing have the smallest footprints to date.

Experimental characterization of an ultra-broadband dual-mode symmetric Y–junction based on metamaterial waveguides

“…This behavior inhibits diffraction and enables refractive index and dispersion engineering [44]. Subwavelength engineering has become a strong design method for the realization of integrated silicon photonics components, including fiber-chip couplers [41], reconfigurable filters [46] and gradient-index lenses [47]. SWG metamaterials have also been successfully applied to several power splitters such as asymmetric directional couplers [48], three-guide directional couplers [49], inverse tapers [45,50], slot adiabatic waveguides [51], MMI devices [52][53][54], waveguide crossings [55] and Y-junctions [56].…”

Temperature tunable Bragg transmission multichannel filters made of two quarter-wave stacks separated by defect layers

“…There are reports on the gratings those work in subwavelength regimes with Ge 2 Sb 2 Te 5 cavity which acts as re-configurable bandpass optical filters [3]. The applications of subwavelength gratings in Si photonics and in high-speed communication are reviewed extensively [4,5]. and n recent times, people have utilized bandpass filters as biosensors, with high sensitivity which have a tremendous lab on chip applications [6].…”

Silicon nitride thin film for optofluidic sensor application

“…Silicon nitride has exceptional optical properties, such as a high refractive index (n = 1.8-2.0), minimal optical loss (n = 1 dB/cm), and wide transparency in the visible and near-infrared ranges [6][7][8][9] . Because of these characteristics, silicon nitride is an excellent substance for the fabrication of waveguides 3 and resonators for optofluidic uses [10][11][12][13] . Silicon nitride's high refractive index allows for the powerful confinement of light in waveguides and resonators, while its low optical loss allows light to travel over long distances without substantial attenuation.…”