A phonon laser
Red-detuned laser pumping of an atomic resonance will cool the motion of an ion or atom. The complementary regime of blue-detuned pumping is investigated in this work using a single, trapped Mg+ ion interacting with two laser beams, tuned above and below resonance. Widely thought of as a regime of heating, theory and experiment instead show that stimulated emission of centre-of-mass phonons occurs, providing saturable amplification of the motion. A threshold for transition from thermal to coherent oscillating motion has been observed, thus establishing this system as a mechanical analogue to an optical laser -— a phonon laser. Such a system has been sought in many different physical contexts.
Additional Information© 2009 Nature Publishing Group. Received 3 January 2009; Accepted 3 July 2009; Published online 16 August 2009. The authors thank P. Toschek for review and comments on the manuscript. K.V. gratefully acknowledges support from the Alexander von Humboldt Foundation and also thanks the California Institute of Technology. T.W.H. gratefully acknowledges support by the Max-Planck Foundation. Author Contributions: M.H., S.K., V.B. and G.S. carried out measurements. K.V., M.H. and Th.U. carried out simulations. K.V., M.H., Th.U. and T.W.H. developed the concepts. All authors worked together to plan the measurements and write the manuscript. Supplementary information accompanies this paper on www.nature.com/naturephysics.
Supplemental Material - nphys1367-s1.pdf