P. Castéra

Influence of BaTiO3 ferroelectric orientation for electro-optic modulation on silicon.

The influence of BaTiO(3) ferroelectric domain orientations for high efficiency electro-optic modulation has been thoroughly analyzed. The Mach-Zehnder modulator structure is based on a CMOS compatible silicon/BaTiO(3)/silicon slot waveguide that supports both TE and TM polarizations whereas the Pockels effect is exploited by the application of a horizontal electric field with lateral electrodes placed on top of the BaTiO(3) layer. The influence of the waveguide parameters has been optimized for each configuration and the lowest V(π) voltage combined with low losses has been determined. A V(π)L as low as 0.27 V·cm has been obtained for a-axis oriented BaTiO(3) and TE polarization by rotating the waveguide structure to an optimum angle.

Electro-Optical Modulation Based on Pockels Effect in BaTiO 3 With a Multi-Domain Structure

The influence of an in-plane multi-domain structure in BaTiO₃ films grown on SrTiO₃/Si buffers for highly efficient electro-optic modulation has been analyzed. The modulation performance can be significantly enhanced by rotating a certain angle, the optical waveguide, with respect to the BaTiO₃ crystallographic axes. A robust electro-optical performance against variations in the domain structure as well as the lowest V_π voltage can be achieved by using the rotation angles between 35° and 55°. Our calculations show that V_π voltages below 1.7 V for a modulation length of 2 mm can be obtained by means of a CMOS compatible hybrid silicon/BaTiO₃ waveguide structure.

Barium titanate (BaTiO 3 ) RF characterization for application in electro-optic modulators

Barium titanate (BaTiO3 or BTO) is currently one of the most promising ferroelectric materials for enabling Pockels modulation that is compatible with silicon photonic circuits. The relative permittivity of BTO has been characterized in thin films deposited on a silicon-on-insulator (SOI) substrate. High values between 800 and 1600 have been estimated at 20 GHz. Furthermore, no substantial difference has been obtained by using BTO grown by molecular beam epitaxy and sputtering. The obtained permittivity has been used to properly design the RF electrodes for high-speed modulation in hybrid BTO/Si devices. Electrodes have been fabricated and the possibility of achieving modulation bandwidths up to 40 GHz has been demonstrated. The bandwidth is limited by the microwave propagation losses and, in this case, different losses have been measured depending on the BTO growth process.

Silicon CMOS compatible transition metal dioxide technology for boosting highly integrated photonic devices with disruptive performance

In this work we will present the objectives and last results of the FP7-ICT-2013-11-619456 SITOGA project. The SITOGA project will address the integration of transition metal dioxides (TMO) materials in silicon photonics and CMOS electronics. TMOs have unique electro-optical properties that will offer unprecedented and novel capabilities to the silicon platform. SITOGA will focus on two disruptive TMO materials, barium titanate (BaTiO3) and vanadium didioxide (VO2), for developing advanced photonic integrated devices for a wide range of applications. Innovative integration processes with silicon photonics circuits and CMOS electronics will be developed. The whole technology chain will be validated by two functional demonstrators: a 40 Gbit/s DPSK transceiver and an 8×8 switching matrix with 100 Gbit/s throughput.

Hybrid silicon-ferroelectric oxide platform for tunable nanophotonics on silicon

In this communication, we present strategies to implement novel or enhanced optoelectronic functionalities on silicon via the monolithic integration of functional oxides as active layers for nanophotonic devices. We focus on the use of ferroelectric oxides with naturally strong electro-optical coefficients such as BaTiO3 (BTO) on SOI for the realization of electro-optical modulators around 1.55 μm. Specifically, we present methods to monolithically integrate monocrystalline BTO on silicon and to design devices that leverage their strong Pockels coefficient for efficient and fast electro-optical modulation. We show preliminary results on the fabrication, process and characterization of a slotted BTO waveguide platform. We further discuss on first electro-optical modulation results and how to improve the current optoelectronic platform. In particular, we will explain the potential origins of optical losses in such systems and how to avoid them.

Towards high-speed electro-optical performance in a hybrid BaTiO 3 /Si Mach-Zehnder modulator

A Mach-Zehnder modulator based on a hybrid BaTiO₃/silicon optical waveguide has been designed to achieve a high modulation bandwidth with a simulated V_πL below 1V·cm and RF impedance matching. The device has been fabricated and characterized in the DC regime.

Integration of functional oxides on SOI for agile silicon photonics

Photonic devices enabling light modulation and switching are of major importance for modern telecommunication. Silicon-based electro-optic modulators are intensively investigated because of their direct compatibility to CMOS fabrication processes. However, the performances of Si based modulators are intrinsically limited, in terms of data transmission rate and energy consumption. To overcome this limitation, ferroelectric oxides with naturally strong electro-optical coefficients combined to small footprint could be ideal candidates for high-speed modulators. We have designed an integration scheme to implement these materials on SOI photonic platform, for 1.55 μm Datacom systems. Monolithic integration of ferroelectric oxides on SOI via SrTiO3 templates is presented. The devices are based on a horizontal (crystalline Si / ferroelectric oxide / amorphous Si) slot waveguide configuration.