Carlos A Alonso-Ramos

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Grating couplers are an efficient means for fiber to chip coupling, as they require no facet preparation and enable wafer scale testing. While grating couplers are commonly used in silicon wire waveguides, their application to micrometric silicon-on-insulator rib waveguides is complicated due to the presence of high-order Bloch modes. We study the Bloch(More)
We present a new type of mid-infrared silicon-on-insulator (SOI) waveguide. The waveguide comprises a sub-wavelength lattice of holes acting as lateral cladding while at the same time allowing for the bottom oxide (BOX) removal by etching. The waveguide loss is determined at the wavelength of 3.8 μm for structures before and after being underetched using(More)
We present several fundamental photonic building blocks based on suspended silicon waveguides supported by a lateral cladding comprising subwavelength grating metamaterial. We discuss the design, fabrication, and characterization of waveguide bends, multimode interference devices and Mach-Zehnder interferometers for the 3715 - 3800 nm wavelength range,(More)
Grating couplers are widely used as an efficient and versatile fiber-chip coupling structure in nanometric silicon wire waveguides. The implementation of efficient grating couplers in micrometric silicon-on-insulator (SOI) rib waveguides is, however, challenging, since the coupler waveguide region is multimode. Here we experimentally demonstrate grating(More)
Polarization handling is a key requirement for the next generation of photonic integrated circuits (PICs). Integrated polarization beam splitters (PBS) are central elements for polarization management, but their use in PICs is hindered by poor fabrication tolerances. In this work we present a fully passive, highly fabrication tolerant polarization beam(More)
We present the first experimental demonstration of a new fiber-chip grating coupler concept that exploits the blazing effect by interleaving the standard full (220 nm) and shallow etch (70 nm) trenches in a 220 nm thick silicon layer. The high directionality is obtained by controlling the separation between the deep and shallow trenches to achieve(More)
Surface grating couplers enable efficient coupling of light between optical fibers and nanophotonic waveguides. However, in conventional grating couplers, the radiation angle is intrinsically wavelength dependent, thereby limiting their operation bandwidth. In this Letter, we present a zero-order surface grating coupler in silicon-on-insulator which(More)
Monolithically integrated polarization management is a key objective for the next generation of high speed optical coherent receivers, and will enable transmission rates up to 400 Gbps. In this work we present a polarization beam splitter (PBS) based on an asymmetrical Mach-Zehnder interferometer (MZI) monolithically integrated with a coherent receiver.(More)
Subwavelength gratings (SWG) are photonic structures with a period small enough to suppress diffraction, thereby acting as artificial dielectric materials, also called all-dielectric metamaterials. This property has been exploited in many high-performance photonic integrated devices in the silicon-on-insulator (SOI) platform. While SWG waveguides are(More)
A photonic integrated architecture realizing the concept of coupled-resonator dual-mode optical filters is presented. The proposed structure consists of a chain of directly coupled microring resonators with a partial reflector embedded in the last resonator. The contradirectional coupling induced by the reflector makes the effective order of the filter(More)