Periodic domain inversion in single crystal barium titanate-on-insulator thin film

TL;DR

This paper demonstrates the first electric field periodic poling of single crystal barium titanate thin films on insulator, enabling advanced nonlinear optical applications and integration into photonic devices.

Contribution

It reports the first successful periodic poling of single crystal BTO thin films, a crucial step for efficient nonlinear optical processes and device integration.

Findings

High-quality, uniform periodic poling achieved with 50% duty cycle.

Poling periods successfully ranged from 2 μm to 10 μm.

Demonstrated potential for quasi-phase-matching in BTO.

Abstract

We report experimentally achieving first-ever electric field periodic poling of single crystal barium titanate (BTO, or BaTiO3) thin film on insulator. Owing to the outstanding optical nonlinearities of BTO, this result is a key step towards achieving quasi-phase-matching in BTO. We first grow the BTO thin film on a dysprosium scandate substrate using pulsed laser deposition with a thin layer of strontium ruthenate later serving as the bottom electrode for poling. We present characterization of the BTO thin film using x-ray diffraction and piezo-response force microscopy to clearly demonstrate single crystal, single domain growth of the film which enables the desired periodic poling. To investigate the poling quality, we apply both non-destructive piezo force response microscopy and destructive etching-assisted scanning electron microscopy and we show that high quality, uniform and intransient poling with 50 % duty cycle and periods ranging from 2 {\mu}m to 10 {\mu}m is achieved. The successful realization of periodic poling in BTO thin film unlocks the potential for highly efficient nonlinear processes under quasi-phase-matching that seemed far-fetched with prior polycrystalline BTO thin films which predominantly relied on efficiency-limited random or non-phase matching conditions and is a key step towards integration of BTO photonic devices.