Naturally Phase-Matched Second-Harmonic Generation in a Whispering-Gallery-Mode Resonator

Abstract

We demonstrate for the first time natural phase matching for optical frequency doubling in a high-$Q$ whispering-gallery-mode resonator made of lithium niobate. A conversion efficiency of 9% is achieved at $30\mu \mathrm{W}$ in-coupled continuous wave pump power. The observed saturation pump power of 3.2 mW is almost 2 orders of magnitude lower than the state-of-the-art value. This suggests an application of our frequency doubler as a source of nonclassical light requiring only a low-power pump, which easily can be quantum noise limited. Our theoretical analysis of the three-wave mixing in a whispering-gallery-mode resonator provides the relative conversion efficiencies for frequency doubling in various modes. DOI: http://dx.doi.org/10.1103/PhysRevLett.104.153901 © 2010 The American Physical Society