Sum-frequency generation of a laser and its background in an on-chip lithium-niobate microdisk

Lithium-niobate microcavities have not only the ability to resonantly enhance light-matter interaction but also excellent nonlinear optical properties, thereby providing an important platform for nonlinear optical investigations. In this paper, we report the observation of multi-peak spectra in the near infrared range in lithium-niobate microcavities on a chip under the pump of a 1550 nm continuous laser. Such a multi-peak spectrum was attributed to the sum-frequency of the pump laser and its background. The conversion efficiencies of the sum-frequency processes are of the order of 61.5% W-1. The influences of the phenomenon on nonlinear processes were further discussed.