Abstract
Subwavelength grating (SWG) metamaterials have garnered a great interest for their singular capability to shape the material properties and the propagation of light, allowing the realization of devices with unprecedented performance. However, practical SWG implementations are limited by fabrication constraints, such as minimum feature size, that restrict the available design space or compromise compatibility with high-volume fabrication technologies. Indeed, most successful SWG realizations so far relied on electron-beam lithographic techniques, compromising the scalability of the approach. Here, we report the experimental demonstration of an SWG metamaterial engineered beam splitter fabricated with deep-ultraviolet immersion lithography in a 300-mm silicon-on-insulator technology. The metamaterial beam splitter exhibits high performance over a measured bandwidth exceeding 186 nm centered at 1550 nm. These results open a new route for the development of scalable silicon photonic circuits exploiting flexible metamaterial engineering.
Highlights
Subwavelength grating (SWG) metamaterials consist of periodic arrangements of dielectric structures with a period substantially smaller than the wavelength of the propagating light
The use of a graded index SWG metamaterial has been recently proposed in a III-V platform to reduce facet reflectivity [21]
We have reported on the use of a 300-mm SOI fabrication platform with DUV immersion lithography to implement a high-performing multi-mode interference (MMI) beam splitter based on an SWG metamaterial
Summary
Subwavelength grating (SWG) metamaterials consist of periodic arrangements of dielectric structures with a period substantially smaller than the wavelength of the propagating light. Several demonstrations of SWG-based devices with features larger than about 120 nm and compatible with dry DUV lithography have been proposed in the literature but this normally constraints the available design space and the range of achievable material properties, making the design more complex and impacting performance [23] For this reason, most of the successful demonstrations have so far relied on electron-beam lithography that offers higher resolution at the expense of a largely reduced throughput which limits its applicability to research or small volume productions. Immersion DUV lithography is compatible with high-volume production and, compared to dry lithography, allows to achieve a three-fold improvement in device size reproducibility, with one-sigma variations below 1% across the wafer, and an almost two times reduction of line edge roughness [24,25]. The fabricated device has a behavior well in line with simulation predictions, exhibiting high performance over a bandwidth exceeding 186 nm
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