Ultralow-linewidth ring laser using hybrid integration and generic foundry platforms.

Two photonic integrated circuits (PICs) are coupled to form a hybridly integrated semiconductor ring laser in the telecom C band with an intrinsic linewidth of (158±21) Hz. This is, to the best of our knowledge, the first time an InP active-passive platform is used in conjunction with an integrated low-loss resonator to obtain a narrow-linewidth laser implemented using generic foundry platforms. The presented results pave the way for a hybrid integrated platform for microwave photonics (MWP), as the demonstrated device includes multiple active-passive components, and its narrow optical linewidth can potentially be translated to a narrow-linewidth microwave signal. Furthermore, as the laser is based on hybrid integration of two PICs from generic foundry platforms, there is a path to reproducible and low-cost devices.

Large Pockels effect in micro- and nanostructured barium titanate integrated on silicon.

The electro-optical Pockels effect is an essential nonlinear effect used in many applications. The ultrafast modulation of the refractive index is, for example, crucial to optical modulators in photonic circuits. Silicon has emerged as a platform for integrating such compact circuits, but a strong Pockels effect is not available on silicon platforms. Here, we demonstrate a large electro-optical response in silicon photonic devices using barium titanate. We verify the Pockels effect to be the physical origin of the response, with r42 = 923 pm V-1, by confirming key signatures of the Pockels effect in ferroelectrics: the electro-optic response exhibits a crystalline anisotropy, remains strong at high frequencies, and shows hysteresis on changing the electric field. We prove that the Pockels effect remains strong even in nanoscale devices, and show as a practical example data modulation up to 50 Gbit s-1. We foresee that our work will enable novel device concepts with an application area largely extending beyond communication technologies.

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.