Simultaneous type-I and type-II phase matching for second-order nonlinearity in integrated lithium niobate waveguide

Area of Science:

• Photonics and optical engineering
• Materials science
• Quantum optics

Background:

• Second-order optical nonlinearity is crucial for classical and quantum photonic devices.
• Material dispersion and phase matching limit device flexibility by pre-defining optical field polarization.
• Typically, only one phase matching condition is achievable in a single device.

Purpose of the Study:

• To demonstrate simultaneous phase matching for both type-I and type-II second-order optical nonlinearity.
• To enhance device flexibility in photonic applications.
• To enable versatile photonic functions using a single engineered device.

Main Methods:

• Fabrication of a thin-film lithium niobate waveguide.
• Engineering waveguide geometry to introduce geometric dispersion.
• Utilizing geometric dispersion to compensate for material dispersion and birefringence.

Main Results:

• Simultaneous phase matching for both type-I and type-II second-order nonlinearities achieved in a single waveguide.
• Verified simultaneous phase matching through polarization-dependent second-harmonic generation.
• Generated correlated photons via parametric down-conversion from the same device.

Conclusions:

• Simultaneous phase matching for multiple nonlinear processes is possible in engineered waveguides.
• Geometric dispersion engineering offers a novel route to enhance device versatility.
• This approach paves the way for more flexible and multifunctional photonic devices.