Low loss monolithic barium titanate on insulator integrated photonics with intrinsic quality factor >1 million

TL;DR

This paper introduces a new dry etching process for monolithic barium titanate photonics, achieving ultra-high quality factors and low propagation losses, enabling advanced integrated optical devices with strong electro-optic effects.

Contribution

It presents the first BTO microresonators with Q-factors over 1 million and the lowest reported waveguide losses in BTO platforms, along with high-performance modulators.

Findings

Intrinsic Q-factor > 1 million in BTO microresonators

Waveguide loss as low as 0.32 dB/cm

High electro-optic coefficient r_eff = 162 pm/V

Abstract

Barium titanate (BTO) has been experiencing a surge of interest for integrated photonics technologies because of its large nonlinear optical coefficients, especially the Pockels coefficient, and in part due to newly available thin-film substrates. In this work, we report on the development of a redeposition-free dry etching technique for monolithic BTO-on-insulator photonics, that produces very low-roughness and high-verticality waveguides. Using this, we experimentally demonstrate the first BTO microresonators with intrinsic Q-factor $> 1$ million, and waveguide propagation loss as small as 0.32 dB/cm, representing the lowest losses reported in any BTO-based integrated platform to date. We additionally demonstrate Mach-Zehnder amplitude modulators with $V_{\pi}L = 0.54$ V$\cdot$cm and effective electro-optic coefficient $r_\text{eff} = 162$ pm/V.