Abstract

On-chip Acousto-optic interaction finds applications in photonic modulators, filters, non-reciprocal light transmitters such as isolators, frequency comb generators and quantum processing of information. The acoustooptic (AO) modulation offers the highest modulation extinction than any other light modulation scheme. There have been demonstrations of such interaction on LiNbO3, GaAs, InP, and AlN [1]. However, integration of the AO modulator offers a more scalable integration opportunity than any other platform. Lead zirconate titanate (PZT) with a very strong piezoelectric coefficient (typically, d₃₁ = 274 pC/N) and electro-mechanical coefficient (k²₃₁ =15%) [2], making it an efficient alternative for acousto-optic interaction. Demonstration of PZT-on-SOI [3] was done using a heterodyne set-up with a sol-gel process. The limitation of this work is the presence of a buffer layer in between PZT and waveguide leads to smaller interaction between SAW and waveguide. In this work, we use Ti/Pt as the remote buffer layer to deposit sputtered PZT, which enables us to fabricate an acousto-optic modulator on SOI. This method increases the interaction between the silicon (Si) waveguide and the SAW wave generated in the PZT layer by getting rid of the intermediate layer on top of the waveguide leading to a refractive index modulation in the Si waveguide as seen in Fig.1(a) schematic.

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