Enhanced coherent microwave-to-optics conversion based on second-order nonlinearity

An efficient microwave-optical frequency conversion scheme is proposed based on the second-order nonlinearity in the atomic system. Due to the magnetic transition driven by a microwave field, the second-order nonlinearity builds up and three-wave mixing process appears. It is interesting to find that a detuned auxiliary transition causes a large second-order nonlinearity, which contributes to the increase of conversion efficiency. The simulation results show that the conversion efficiency could be increased by five times. Other effects on the conversion efficiency are also discussed.