Sum-frequency generation in on-chip lithium niobate microdisk resonators

We report the first observation, to the best of our knowledge, of sum-frequency generation in on-chip lithium niobate microdisk resonators. The sum-frequency signal in the 780 nm band, distinct in wavelength from second-harmonic signals, was obtained in lithium niobate microresonators under the pump of two individual 1550 nm band lasers. The sum-frequency conversion efficiency was measured to be 1.4×10−7  mW−1. The dependence of the intensities of the nonlinear signals on the total pump power and the wavelength of one pump laser was investigated while fixing the wavelength of the other. This work paves the way for applications of on-chip lithium niobate microdisk resonators ranging from infrared single-photon detection to infrared spectroscopy.