Intracavity second-harmonic generation using an electromagnetically induced transparency

We analyze the quantum-fluctuation properties of second-harmonic radiation generated in the high-efficiency conversion process used in a recent experiment by Hakuta, Marmet, and Stoicheff [Phys. Rev. Lett. 66, 596 (1991)]. We extend their work by studying the second-harmonic generation inside an optical cavity. The active medium inside the cavity is modeled by three-level atoms with degenerated upper levels (1s, 2p, and 2s states of atomic hydrogen) interacting with a strong constant electric field. An enhancement of the conversion efficiency and a reduction of the added noise are found as a result of an electromagnetically induced transparency. We show that the scheme is capable of producing light in a squeezed or coherent state close to a minimum-uncertainty state with a large mean amplitude.