Phase-Matched Second-Harmonic Generation in an On-Chip LiNbO3 Microresonator

Applications in optics and photonics, such as frequency doubling of a laser, require compact, efficient hardware. The authors demonstrate highly efficient nonlinear frequency conversion in a microdisk resonator about 100 $\ensuremath{\mu}$m across. The key to efficiency in this parametric process is phase matching, which becomes more difficult at smaller length scales. This achievement is a significant step toward chip-integrated nonlinear optical devices.