Influence of BaTiO_3 ferroelectric orientation for electro-optic modulation on silicon

Abstract

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 BaTiO3With a Multi-Domain Structure

“…Finally, the waveguide structure is covered by a SiO 2 cladding. The waveguide parameters, which are also depicted in Fig.1(a), have been optimized by simulations [16]. The thickness of the silicon layer in the SOI wafer is t Si =100 nm and the BTO thickness is t BTO =50 nm.…”

“…Epitaxial growth of BTO films offers the possibility to select the direction in which the spontaneous polarization can appear depending on the desired application [18]. In this work, we will consider purely a-axis oriented BTO films as it has been shown to provide better EO performance [15,16].…”

“…In our previous work [16], the optimum BTO ferroelectric domain orientation to enhance the EO modulation was analyzed assuming a single domain orientation, achieving a Vπ·Lπ as low as 0.27 V·cm. However, a multi-domain structure is usually formed during the fabrication of BaTiO 3 layers [17,18].…”

Development of new photonic devices based on barium titanate in silicon

“…Furthermore, the potential of growing high-quality thin film crystalline layers of BTO on strontium titanate (SrTiO3) templated silicon and silicon on insulator (SOI) substrates [12,49,50] has recently opened a path towards the development of hybrid BTO silicon EO modulators with disruptive performance [51][52][53][54][55][56]. Table 1.1 summarizes the BaTiO3 properties at 1550nm optical wavelength and the enhanced capabilities offered to the silicon platform.…”

“…A new recipe with a low temperature of 225ºC 3.3. Low loss amorphous silicon 53 was obtained with a refractive index of 3.47 (Recipe 2 in Table 3.2). Nevertheless, this recipe led to high stress in the a-Si layer and therefore the quality of the material was decreased.…”