Ultra-broadband nanophotonic beamsplitter using an anisotropic sub-wavelength metamaterial

• Published in: Laser & photonics reviews Vol. 10; no. 6; pp. 1039 - 1046
• Main Authors: Halir, Robert, Cheben, Pavel, Luque-González, José Manuel, Sarmiento-Merenguel, Jose Darío, Schmid, Jens H., Wangüemert-Pérez, Gonzalo, Xu, Dan-Xia, Wang, Shurui, Ortega-Moñux, Alejandro, Molina-Fernández, Íñigo
• Format: Journal Article
• Language: English
• Published: Weinheim Blackwell Publishing Ltd 01.11.2016; Wiley Subscription Services, Inc
• Subjects: Anisotropy; Bandwidth; broadband; Design engineering; Metamaterials; multimode interference; Nanostructure; Photonics; Platforms; silicon photonics; Telecommunications; Telecommunications industry
• ISSN: 1863-8880; 1863-8899
• DOI: 10.1002/lpor.201600213

Nanophotonic beamsplitters are fundamental building blocks in integrated optics, with applications ranging from high speed telecom receivers to biological sensors and quantum splitters. While high‐performance multiport beamsplitters have been demonstrated in several material platforms using multimode interference couplers, their operation bandwidth remains fundamentally limited. Here, we leverage the inherent anisotropy and dispersion of a sub‐wavelength structured photonic metamaterial to demonstrate ultra‐broadband integrated beamsplitting. Our device, which is three times more compact than its conventional counterpart, can achieve high‐performance operation over an unprecedented 500 nm design bandwidth exceeding all optical communication bands combined, and making it one of the most broadband silicon photonics components reported to date. Our demonstration paves the way toward nanophotonic waveguide components with ultra‐broadband operation for next generation integrated photonic systems. The inherent anisotropy of a sub‐wavelength metamaterial is exploited for ultra‐broadband on‐chip beamsplitting in the silicon‐on‐insulator platform. By examining the principle of self‐imaging in anisotropic media an analytic design expression is established. High performance operation is experimentally demonstrated over a bandwidth of more than 300nm at telecom wavelengths, with full‐wave simulations indicating that over 500nm are attainable.