Fürst, J. U.3; Strekalov, D. V.3; Elser, D.3; Aiello, A.3; Andersen, Ulrik Lund2; Marquardt, Ch.3; Leuchs, G.3
1 Quantum Physics and Information Techology, Department of Physics, Technical University of Denmark2 Department of Physics, Technical University of Denmark3 Max Planck Institute
Optical parametric down-conversion has proven to be a valuable source of nonclassical light. The process is inherently able to produce twin-beam correlations along with individual intensity squeezing of either parametric beam, when pumped far above threshold. Here, we present for the first time the direct observation of intensity squeezing of -1.2 dB of each of the individual parametric beams in parametric down-conversion by use of a high quality whispering-gallery-mode disk resonator. In addition, we observed twin-beam quantum correlations of -2.7 dB with this cavity. Such resonators feature strong optical confinement and offer tunable coupling to an external optical field. This work exemplifies the potential of crystalline whispering-gallery-mode resonators for the generation of quantum light. The simplicity of this device makes the application of quantum light in various fields highly feasible.