Over the past 15 years since their first demonstration, subwavelength grating metamaterials in silicon photonic devices have become widely used and attracted rapidly growing research interest while also breaking into commercial applications. We will discuss recent advances in this research field, with a focus on novel components and circuits for beam steering applications, on-chip filtering and quantum optics. On-chip optical waveguides comprised of Mie resonant particle chains have only recently been demonstrated and promise to be the foundation of a new and exciting branch of integrated metamaterials research. We will review the early work in this area.
Quantum photonics has emerged as a key driver for advancing applications, such as quantum communication and sensing, that harness the potential of quantum effects beyond classical capabilities. Photonic integrated circuits favor such implementations by providing low loss and interferometric stability. Nonetheless, to fully leverage these advantages, two major challenges need to be addressed: highly efficient fiber-to-chip light coupling and waveguide-integrated single-photon detection. In this work, we utilize subwavelength grating (SWG) metamaterials to design (i) novel off-chip couplers enabling sub-decibel coupling efficiency and (ii) a new superconducting nanowire single-photon detector (SNSPD) concept featuring enhanced photon absorption and fast detection.
Subwavelength materials have become a fundamental tool for silicon photonic design, enabling devices with unique performance characteristics. We will briefly review some fundamentals here and will then discuss some of the latest advances in the field, with a particular focus on polarization handling. Furthermore, we will discuss advances in integrated optical sensing, addressing both fundamental issues such as the optimization of detection limits, as well as state-of-the-art results with novel sensing architectures. We will also discuss which benefits subwavelength structures can provide in such sensors.
In this talk we present our recent advances in SWG metamaterial engineering. We will show a 1D-optical phased array composed of 112 evanescent-coupled surface emitting antennas with a length of 1.5 mm and fed by a compact distributed Bragg deflector. The measurements demonstrate a wavelength-steerable collimated beam with a far-field angular divergence of 1.8o × 0.2o. Experimental results of a bricked SWG 2×2 MMI coupler are also shown, achieving polarization agnostic performance in the 1500nm to 1560nm wavelength range. Both devices were fabricated on a standard 220-nm SOI platform using a single full-etch step process, with a minimum feature size of 80 nm, and thus compatible with immersion deep-UV lithography.
We present two novel topologies of subwavelength grating (SWG) waveguides: the bricked-SWG and the evanescently-coupled-SWG. The bricked topology enables accurate control of waveguide anisotropy while maintaining the index and dispersion engineering advantage intrinsic to SWG waveguides. The evanescently-coupled-SWG allows unprecedented control of the strength of the modal perturbation in waveguide Bragg gratings and nanophotonic antennas. Both topologies leverage a Manhattan-like pattern, with pixel sizes compatible with deep-uv lithography. Our recent results will be discussed, focusing on polarization-independent multimode interference couplers for the O and C bands and a millimeter-long narrow-beam steerable optical antenna array with angular divergence of only 1.8o×0.2o.
Subwavelength grating metamaterials have become an integral design tool in silicon photonics. The lithographic segmentation of integrated waveguides at the subwavelength scale allows us to control optical properties such as mode delocalization, wavelength dispersion, and birefringence. So far, a range of subwavelength-based devices with unprecedented performance has been demonstrated, such as couplers, polarization-handling structures, filters, and input/output chip interfaces. In this invited talk, we will review the anisotropic foundations of subwavelength-grating metamaterial design and will provide an overview of our latest advances in subwavelength-enhanced silicon photonics devices, including optical antennas for beam steering and multi-line Bragg filters for spectral shaping.
Silicon nitride (SiNx), has been widely regarded as a CMOS photonics enabling material, facilitating the development of low-cost CMOS compatible waveguides and related photonic components. We have previously developed an NH3-free SiN PECVD platform in which its optical properties can be tailored. Here, we report on a new type of surface-emitting nitrogen-rich silicon nitride waveguide with antenna lengths of L < 5 mm. This is achieved by using a technique called small spot direct ultraviolet writing, capable of creating periodic refractive index changes ranging from -0.01 to -0.04. With this arrangement, a weak antenna radiation strength can be achieved, resulting in far-field beam widths < 0.0150, while maintaining a minimum feature size equal to 300 nm, which is compatible with DUV scanner lithography.
Silicon photonic waveguides patterned at the subwavelength level behave as metamaterials whose optical properties, including refractive index, dispersion and anisotropy can be tuned by judiciously designing the subwavelength geometry. Over the past years, the added design freedom afforded by these structures has enabled a wide variety of novel high performance devices, ranging from high efficiency fibre-to-chip couplers, to on-chip polarization and mode management, and ultra-broadband waveguide couplers covering several optical communication bands. In this invited keynote talk we will revisit the physical foundations of these structures, explore some of the latest advances in the field with applications in both telecommunications and sensing, and discuss some of the outstanding challenges to move these structures from research labs to large-scale commercialisation.
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