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11 pages, 3191 KiB

Open AccessEditor’s ChoiceArticle

Ultra-Broadband, Compact Arbitrary-Ratio Multimode Power Splitter Based on Tilted Subwavelength Gratings

by Wenbin Chen, Hongjie Guo, Yongkang Yang, Baiang Qu, Yali Zhao, Yingchun Cao, Wentao Guo and Manqing Tan

Photonics 2023, 10(12), 1327; https://doi.org/10.3390/photonics10121327 - 29 Nov 2023

Cited by 2 | Viewed by 1824

Abstract

Mode division multiplexing (MDM) technology is an effective solution for high-capacity optical interconnection, and multimode power splitters, as essential components in MDM systems, have attracted widespread attention. However, supporting a wide range of modes and arbitrary power splitting ratios with large bandwidth in power splitters remains a significant challenge. In this paper, we designed a power splitter based on a subwavelength grating (SWG) structure with tilted placement on a silicon-on-insulator (SOI) substrate. We achieve arbitrary TE₀–TE₉ mode-insensitive power distribution by altering the filling coefficient of the SWG. Thanks to our specific selection of cladding materials and compensatory design for the optical wave transmission and reflection shifts induced by SWG, our device demonstrates low additional loss (EL < 1.1 dB) and inter-mode crosstalk (−18.8 < CT < −60 dB) for optical modes ranging from TE₀ to TE₉, covering a wavelength range from 1200 nm to 1700 nm. Furthermore, our proposed device can be easily extended to higher-order modes with little loss of device performance, offering significant potential in MDM platforms. Full article

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10 pages, 4178 KiB

Open AccessArticle

On-Chip Design of a Broadband 850 nm TM-Pass/TE-Stop Polarizer with Tilted Subwavelength Gratings

by Yue Dong, Yu Liu, Yin Xu and Bo Zhang

Symmetry 2022, 14(11), 2359; https://doi.org/10.3390/sym14112359 - 9 Nov 2022

Cited by 3 | Viewed by 1758

Abstract

An integrated TM-pass/TE-stop polarizer centered at 850 nm is designed in this paper. The proposed polarizer is designed on a Si₃N₄ on insulator platform with tilted subwavelength gratings (SWG). Since the tilted SWGs have much more of an impact on the effective index of the TE polarization state than that of the TM polarization state, they help to achieve high TM and low TE transmission simultaneously. After geometries optimization, the polarizer’s working bandwidth, which is defined as the wavelength region with an extinction ratio higher than 20 dB, is determined to be 185 nm under a SWG tilting angle of 30 degrees. At the same time, the insertion loss is always less than 0.45 dB over the entire working wavelength band. Finally, the results of fabrication tolerance analysis show that the SWG ridge width jitter only degrades the polarizer’s working bandwidth by 16 nm. Full article

(This article belongs to the Special Issue Advances in Optics and Symmetry/Asymmetry)

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10 pages, 3578 KiB

Open AccessArticle

Ultra-Thin, Short-Focus, and High-Aperture Metalens for Generating and Detecting Laser Optical Vortices

by Anton Nalimov and Victor Kotlyar

Nanomaterials 2022, 12(15), 2602; https://doi.org/10.3390/nano12152602 - 28 Jul 2022

Cited by 9 | Viewed by 2354

Abstract

A combined high-aperture metalens in a thin silicon nitride film that consists of two tilted sectored metalenses is considered. Each sector of the metalens consists of a set of binary subwavelength gratings. The diameter of the metalens is 14 μm. Using a time-domain finite difference method, we show that the metalens can simultaneously detect optical vortices with two topological charges −1 and −2, almost over the entire spectrum of visible wavelengths. The metalens can distinguish several wavelengths that are focused at different points in the focal plane due to a 1-nm change in wavelength resulting in a focal spot shift of about 4 nm. When the metalens is illuminated by a Gaussian beam with left-handed circular polarization, two optical vortices with topological charges 1 and 2 are simultaneously formed 6-μm apart at the focal distance of 6 μm. Full article

(This article belongs to the Special Issue Metasurfaces for Photonic Devices: Theory and Applications)

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