Periodic Domain Inversion in Single Crystal Barium Titanate‐on‐Insulator Thin Film

Abstract Experimentally achieving the first‐ever electric field periodic poling of single crystal barium titanate oxide (BTO, or BaTiO₃) thin film on‐insulator is reported. Owing to the outstanding optical nonlinearities of BTO, this result is a key step toward achieving quasi‐phase‐matching (QPM). First, the BTO thin film is grown on a dysprosium scandate substrate using pulsed laser deposition with a thin layer of strontium ruthenate later serving as the bottom electrode for poling. The characterization of the BTO thin film using x‐ray diffraction (XRD) and piezo‐response force microscopy to demonstrate single crystal, single domain growth of the film that enables the desired periodic poling, are presented. To investigate the poling quality, both non‐destructive piezo force response microscopy and destructive etching‐assisted scanning electron microscopy (SEM) are applied, and it is shown that high quality, uniform, and intransient poling with 50% duty cycle and periods ranging from 2 µm to 10 µm is achieved. The successful realization of periodic poling in BTO thin film unlocks the potential for highly efficient nonlinear processes under QPM 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 toward integration of BTO photonic devices.