Quantum Nonlinear Optics is an effort focused on fabricating devices that can enable breakthroughs in integrated photonics in the coming years. In this branch of the lab, we focus on interactions between photons in nonlinear media. They can be especially strong in materials like lithium niobate (LiNbO3, LN), where just three photons can interact with each other through the second-order nonlinearity χ(2). Harnessing these effects can be used in a range of applications from wavelength conversion, through enhanced metrology, to engineering quantum states of light and using it for quantum computing. We have developed novel nanophotonic lithium niobate devices with strong light confinement that significantly enhances nonlinearity and allows electro-optic control. This provides an excellent platform to use scientific developments of the last 60 years to push the industry frontier.
Our group provides a rare combination of expertise in nanofabrication, periodic poling, and numerical design of photonic circuits, allowing end-to-end device fabrication and characterization. The high-quality fabrication process allows us to make on-chip waveguides with negligible propagation loss and microresonators characterized by intrinsic quality factors higher than 2 million. Periodic poling is a way for controlled crystal domain engineering, which provides a way to satisfy momentum matching of arbitrary interaction. This combination allows us to make devices working across the visible, near-, and mid-IR spectrum. Recently, we have developed fully-resonant devices for efficient second-harmonic generation and optical parametric oscillators that operate within the near-IR with sub-100μW threshold [arXiv:2102.05617]. These devices are essential building blocks for the on-chip quantum light generation, photonic quantum computing, and enhanced metrology. The second branch of the nonlinear optical effort concentrates on mid-IR light generation on-chip and using it in integrated gas sensors, including devices for monitoring greenhouse gases. As a proof of concept, we developed an LN/Sapphire platform and successfully generated light around 3μm [Optica 8, 921 (2021)].