Srico (United States)

Barium titanate is a highly desired material for the development of advanced linear phase modulators due to the exceptionally large value of its electro-optic coefficient. While attempts have been made in the past to utilize this material property, the overall device performance has not been as sensitive as expected due to a number of special considerations that were not made as a result of the off-diagonal nature of barium titante's electro-optic coefficient. This work discusses these special considerations, presents an in-house characterization technique that is being developed specific to these off-diagonal coefficients, and demonstrates preliminary device designs for a high-performance barium titanate modulator.

This article describes the processing, characterization, and transfer of 25 μm-thick by 480 μm-long iron-garnet Faraday rotator films onto semiconductor substrates. Insertion losses below 0.1dB and extinction ratios of -30 dB are achieved. No magnets are needed.

We demonstrate a photonic waveguide technology based on a two-material core, in which light is controllably and repeatedly transferred back and forth between sub-micron thickness crystalline layers of Si and LN bonded to one another, where the former is patterned and the latter is not. In this way, the foundry-based wafer-scale fabrication technology for silicon photonics can be leveraged to form lithium-niobate based integrated optical devices. Using two different guided modes and an adiabatic mode transition between them, we demonstrate a set of building blocks such as waveguides, bends, and couplers which can be used to route light underneath an unpatterned slab of LN, as well as outside the LN-bonded region, thus enabling complex and compact lightwave circuits in LN alongside Si photonics with fabrication ease and low cost.

The linear electro-optic effect in lithium niobate is capable of realizing a variety of polarization transformations, including TE-to-TM and left-to-right circular polarization conversion. While most LiNbO₃ components are designed for operation in the third telecommunications window around 1.55 μm wavelength, current interest in quantum information processing and atomic physics, where the wavelengths of interest are in the visible and near-infrared, has placed new demands on endless polarization control devices. At short wavelengths, traditional Ti-diffused LiNbO₃ waveguides suffer from photorefractive degradation at optical power levels well below 1 mW. Proton exchanged waveguides have much higher power handling capability but can only guide light polarized parallel to the optic axis, and therefore are not applicable to polarization control. Zinc oxide diffusion is an alternative waveguide fabrication technology that guides both e- and o-waves with much higher power handling capability than Ti:LiNbO₃ waveguides. ZnO:LiNbO₃ waveguides exhibit a highly circular mode field with lower anisotropy than Ti-diffused waveguides. We report on the modeling, fabrication and testing of a polarization controller in ZnO-doped, x-cut lithium niobate operating at a wavelength of 780 nm.