Optical-parametric-oscillation-based χ⁽²⁾ frequency comb in a lithium niobate microresonator

Microresonator frequency combs based on the χ (3) nonlinearity are nowadays well understood and making their way into different applications. Recently, microresonator (2) receiving increasing attention, as they promise certain benefits, but still require further study. Here, we present first indication of comb generation, initiated via optical parametric oscillation (OPO) in a lithium niobate mm-sized microresonator. By pumping at 532 nm with 300 µW power, observe 1-THz-wide spectra around 1064 degenerate non-degenerate states. We also show that generation requires signal idler waves to be mode numbers how fulfillment this condition can identified from temperature tuning curves. The results demonstrate potential directly generate OPO beyond 3 μ m wavelengths mid-IR by puming near-IR region.