General-purpose programmable photonic processor for advanced radiofrequency applications.

A general-purpose photonic processor can be built integrating a silicon photonic programmable core in a technology stack comprising an electronic monitoring and controlling layer and a software layer for resource control and programming. This processor can leverage the unique properties of photonics in terms of ultra-high bandwidth, high-speed operation, and low power consumption while operating in a complementary and synergistic way with electronic processors. These features are key in applications such as next-generation 5/6 G wireless systems where reconfigurable filtering, frequency conversion, arbitrary waveform generation, and beamforming are currently provided by microwave photonic subsystems that cannot be scaled down.

Modeling amplified arbitrary filtered heterodyne microwave photonic links.

We report an end-to-end analytic model for the computation of the figures of nerit (FOMs) of arbitrarily filtered and amplified heterodyne coherent microwave photonics (MWP) links. It is useful for evaluating the performance of complex systems where the final stage is employed for up/down-converting the radio frequency (RF) signal. We apply the model to a specific case of complex system representing the front-haul segment in a 5G link between the central office and the base station.

Dual-band fiber-chip grating coupler in a 300 mm silicon-on-insulator platform and 193 nm deep-UV lithography.

Surface grating couplers are fundamental building blocks for coupling the light between optical fibers and integrated photonic devices. However, the operational bandwidth of conventional grating couplers is intrinsically limited by their wavelength-dependent radiation angle. The few dual-band grating couplers that have been experimentally demonstrated exhibit low coupling efficiencies and rely on complex fabrication processes.

Silicon subwavelength modal Bragg grating filters with narrow bandwidth and high optical rejection.

Waveguide Bragg grating filters with narrow bandwidths and high optical rejections are key functions for several advanced silicon photonics circuits. Here, we propose and demonstrate a new, to the best of our knowledge, Bragg grating geometry that provides a narrowband and high rejection response. It combines the advantages of subwavelength and modal engineering.

Dual-polarization silicon nitride Bragg filters with low thermal sensitivity.

Wideband and polarization-independent wavelength filters with low sensitivity to temperature variations have great potential for wavelength division multiplexing applications. However, simultaneously achieving these metrics is challenging for silicon-on-insulator photonics technology. Here, we harness the reduced index contrast and the low thermo-optic coefficient of silicon nitride to demonstrate waveguide Bragg grating filters with wideband apolar rejection and low thermal sensitivity.

SiGe-enhanced Si capacitive modulator integration in a 300 mm silicon photonics platform for low power consumption.

The successful integration of capacitive phase shifters featuring a p-type strained SiGe layer in a 300 mm silicon photonics platform is presented. The phase shift is evaluated with a voltage swing of only 0.9 V, compatible with CMOS technology.

Diffraction-less propagation beyond the sub-wavelength regime: a new type of nanophotonic waveguide.

Sub-wavelength grating (SWG) metamaterials have garnered a great interest for their singular capability to shape the propagation of light. However, practical SWG implementations are limited by fabrication constraints, such as minimum feature size. Here, we present a new nanophotonic waveguide grating concept that exploits phase-matching engineering to suppress diffraction effects for a period three times larger than those with SWG approaches.

Subwavelength engineering and asymmetry: two efficient tools for sub-nanometer-bandwidth silicon Bragg filters.

Bragg filters stand as key building blocks of the silicon-on-insulator (SOI) photonics platform, allowing the implementation of advanced on-chip signal manipulation. However, achieving narrowband Bragg filters with large rejection levels is often hindered by fabrication constraints and imperfections. Here, we show that the combination of single-side corrugation asymmetry and subwavelength engineering provides a narrowband response with large corrugations, overcoming minimum feature size constraints of conventional Si Bragg filters.

L-shaped fiber-chip grating couplers with high directionality and low reflectivity fabricated with deep-UV lithography.

Grating couplers enable position-friendly interfacing of silicon chips by optical fibers. The conventional coupler designs call upon comparatively complex architectures to afford efficient light coupling to sub-micron silicon-on-insulator (SOI) waveguides. Conversely, the blazing effect in double-etched gratings provides high coupling efficiency with reduced fabrication intricacy.

Low voltage 25Gbps silicon Mach-Zehnder modulator in the O-band.

In this work, a 25 Gb ps silicon push-pull Mach-Zehnder modulator operating in the O-Band (1260 nm - 1360 nm) of optical communications and fabricated on a 300 mm platform is presented. The measured modulation efficiency (VπLπ) was comprised between 0.95 V cm and 1.

Optical pump-rejection filter based on silicon sub-wavelength engineered photonic structures.

The high index contrast of the silicon-on-insulator (SOI) platform allows the realization of ultra-compact photonic circuits. However, this high contrast hinders the implementation of narrow-band Bragg filters. These typically require corrugation widths of a few nanometers or double-etch geometries, hampering device fabrication.

Germanium-on-silicon mid-infrared grating couplers with low-reflectivity inverse taper excitation.

A broad transparency range of its constituent materials and compatibility with standard fabrication processes make germanium-on-silicon (Ge-on-Si) an excellent platform for the realization of mid-infrared photonic circuits. However, the comparatively large Ge waveguide thickness and its moderate refractive index contrast with the Si substrate hinder the implementation of efficient fiber-chip grating couplers. We report for the first time, to the best of our knowledge, a single-etch Ge-on-Si grating coupler with an inversely tapered access stage, operating at a 3.

Sharp bends and Mach-Zehnder interferometer based on Ge-rich-SiGe waveguides on SiGe graded buffer.

The integration of germanium (Ge)-rich active devices in photonic integrated circuits is challenging due to the lattice mismatch between silicon (Si) and Ge. A new Ge-rich silicon-germanium (SiGe) waveguide on graded buffer was investigated as a platform for integrated photonic circuits. At a wavelength of 1550 nm, low loss bends with radii as low as 12 µm and Multimode Interferometer beam splitter based on Ge-rich SiGe waveguide on graded buffer were designed, fabricated and characterized.

Evanescent field waveguide sensing with subwavelength grating structures in silicon-on-insulator.

We explore, to the best of our knowledge, the potential of diffractionless subwavelength grating waveguides for sensing applications. We show that by subwavelength patterning of silicon-wire waveguides the field delocalization can be engineered to increase the sensitivity. Fully vectorial 3D-FDTD simulations confirm the sensitivity enhancement, achieving sensitivities of 0.