Pure phase optical modulation based on Pockels effect in strained silicon

Published : 8 February 2020

The use of silicon photonics has been identified as a mean to overcome interconnect limitations and efficiency, but also as a versatile platform able to address the new problematics encountered in Lidar and quantum photonics applications. However, the possibility to have high-speed pure phase optical modulation has not been addressed yet on this platform. Silicon, as a centrosymmetric material does not exhibits second order non-linearities. Nevertheless, it has been theoretically and experimentally demonstrated that by applying a mechanical strain, its centrosymmetric can be broken, leading to the exhibition of second order non-linearities. Recent proofs of concept have been demonstrated with a modulation at 20GHz based on the use of silicon nitride stress layers deposited by PECVD on top of silicon.

The objectives of the PhD will be to enhance the Pockels effect in silicon waveguides by a factor of 10 to 100, in order to reach performances close to LiNbO3. This research activity will include : Fine theoretical study of the involved processes and how to control them, and also electro-optic simulations in order to evaluate the performances of such devices and optimize the overlap between the strain field and the optical mode in the waveguide; The design and fabrication of optical phase modulators optimized to maximize the Pockels effect in the waveguide; DC and RF characterization of optoelectronics devices bas on second order non-linearities.

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