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.
Subwavelength grating (SWG) metamaterials consist of periodic arrangements of dielectric structures with a period substantially smaller than the wavelength of the propagating light. Within this regime, the grating effectively acts as a homogeneous material whose optical properties (e.g., effective index, dispersion, and anisotropy) are determined by the ensemble of the constituent materials and can be varied by properly designing the geometry of the grating unit cells. This type of metamaterials have been successfully implemented in particular in silicon photonic waveguides, allowing an unprecedented control over the field distribution and propagation properties of the guided modes, largely increasing design flexibility compared to conventional waveguides 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.
Here, we exploit a fabrication technology based on 300-mm SOI wafers and immersion DUV lithography to experimentally demonstrate a broadband integrated beam splitter based on an SWG-engineered multi-mode interference (MMI) coupler. The device has a silicon thickness of 300 nm and nominal minimum feature size of 75 nm, well below the resolution capabilities of dry DUV lithography. We believe that the use of lithographic techniques routinely available in complementary metal-oxide-semiconductor (CMOS) processes will be of fundamental importance to bring the potentialities of refractive index engineering toward commercial exploitation. This will enable the fabrication of high-performance devices for fiber-to-chip coupling, power splitting, polarization management, and spectral filtering, with promising applications, for example, in coherent communications, sensing, and spectroscopy.
- Références
Metamaterial-Engineered Silicon Beam Splitter Fabricated with Deep UV Immersion Lithography
Vladyslav Vakarin1,†,‡, Daniele Melati1,*,‡ , Thi Thuy Duong Dinh1, Xavier Le Roux1, Warren Kut King Kan2, Cécilia Dupré2, Bertrand Szelag2, Stéphane Monfray3, Frédéric Boeuf3, Pavel Cheben4,5, Eric Cassan1, Delphine Marris-Morini1, Laurent Vivien1 and Carlos Alberto Alonso-Ramos1
Nanomaterials 2021, 11(11), 2949
https://doi.org/10.3390/nano11112949
- Affiliations
1Centre de Nanosciences et de Nanotechnologies, CNRS, Université Paris-Saclay, 91120 Palaiseau, France
2LETI, University Grenoble Alpes and CEA, 38054 Grenoble, France;
3STMicroelectronics SAS, 850 rue Jean Monnet, 38920 Crolles, France;
4National Research Council Canada, 1200 Montreal Road, Ottawa, ON K1A 0R6, Canada
5Center for Research in Photonics, University of Ottawa, Ottawa, Ontario K1N 6N5, Canada
*Corresponding author : daniele.melati@c2n.upsaclay.fr
Figure 1 : 1. Top panel: Optical image of 300-mm SOI wafer. Bottom panel: Scanning electron microscope image of the fabricated Metamaterial-Engineered Silicon Beam Splitter. Minimum feature size is 75 nm.
