A new technique for producing low-loss BSO waveguides

Isotropic sillenite crystals such as Bismuth Silicon Oxide (BSO) present highly interesting opto-electronics properties including electro-optic effect and photorefractivity. BSO is also a highly suitable candidate for sensitive temperature-independent electric field sensors [1]. Then the production of low cost BSO-based optical-waveguides is becoming a major challenge. However, BSO high density (> 7 g.cm3) and non-standard dimensions are a hurdle for standard fabrication approaches such as ion diffusion or exchange and standard clean-room technologies. Here we report for the first time the successful fabrication of low loss BSO ridge waveguides with high index contrast. The proposed technique is based on optical-grade dicing [2], which allows low cost and massive production of photonic devices in different types of material. Ridge waveguides are made in a 15-μm thick chemical mechanical polished thin layer of BSO bonded on a lithium-niobate wafer. Propagation losses, group velocity and modal birefringence of optical modes have been measured by Optical-Coherence-Tomography. The waveguides support both TE and TM guided modes at telecom wavelength (1.55 μm) and present propagation losses lower than 2 dB/cm. This approach promises to be powerful for shaping single crystal thin films even in exotic formats. We expect low loss optical-waveguide in BSO will pave the way toward