Effect of thickness variations of lithium niobate on insulator waveguide on the frequency spectrum of spontaneous parametric down-conversion*

We study the effect of waveguide thickness variations on the frequency spectrum of spontaneous parametric down-conversion in the periodically-poled lithium niobate on insulator (LNOI) waveguide. We analyze several variation models and our simulation results show that thickness variations in several nanometers can induce distinct effects on the central peak of the spectrum, such as narrowing, broadening, and splitting. We also prove that the effects of positive and negative variations can be canceled and thus lead to a variation-robust feature and an ultra-broad bandwidth. Our study may promote the development of on-chip photon sources in the LNOI platform, as well as opensup a way to engineer photon frequency state.

Automated summary

The study shows that variations in thickness of a periodically poled lithium niobate on insulator (LNOI) waveguide can have different effects on the central peak of the spectrum, such as narrowing, broadening, and splitting. It is also demonstrated that positive and negative variations can cancel each other out, leading to a robust feature and an ultra-wide bandwidth. This research promotes the development of on-chip photon sources in the LNOI platform and provides a new way to engineer photon frequency state.