Cooling mirrors with light Jack Harris, Yale University, PHY 0555824

1. Cooling mirrors with lightJack Harris, Yale University,PHY 0555824 We have realized a new type of optomechanical coupling which allows us to greatly increase the effect of radiation pressure on micromechanical devices. We placed a 50 nm-thick, 1 mm square membrane inside a high-finesse Fabry-Perot cavity. By optimizing the membrane’s mechanical quality factor and the cavity’s finesse, we were able to laser cool the membrane a factor of 100 beyond what had been achieved previously, from 300 K to 7 mK. Measurements of the Brownian motion of a 1 mm x 1 mm x 50 nm silicon nitride membrane. The membrane is placed inside an optical cavity with a finesse of 15,000. As the laser illuminating the cavity is red-detuned slightly from resonance, the membrane experiences increased damping due to radiation pressure. The fits to each data set show the membrane’s mean-square displacement (which is a measure of its temperature) decreasing. The effective temperature extracted from each data set is also shown 10-26 Teff = 2.34 K ± 0.13 K 10-27 Sx(n) (m2/Hz) Teff = 253 mK ± 4.7 mK optimizing laser detuning 10-28 Teff = 80 mK ± 1.8 mK 10-29 Teff = 13.3 mK ± 0.51 mK 10-30 Teff = 6.82 mK ± 0.61 mK 10-31 126 128 130 132 134 n (kHz) This “membrane in the middle” approach utilizes a dispersive coupling between the cavity and the membrane. Dispersive coupling is often used in atom/cavity experiments, but had not yet been realized in optomechanical systems. In addition to allowing for higher cavity finesse and mechanical quality factors, this new approach makes it possible to measure the square of the membrane’s displacement. Such a “displacement-squared” read-out will be crucial for measuring quantum jumps of a mechanical oscillator, a long standing goal in the field of quantum measurement. Our manuscript describing these results is under review at Nature. *30% Co-funded by DMR*

2. Cooling mirrors with lightJack Harris, Yale University,PHY 0555824 BROADER IMPACT: Our group has lead the establishment of a new Gordon Conference on mechanical systems in the quantum regime. This conference will provide an important nexus for developing collaborations and communication within this rapidly-emerging interdisciplinary field. EDUCATION: Two undergraduates and three graduate students have worked on this project in the last year. Both undergrads graduated from Yale this June and both will pursue physics Ph.D.’s at Harvard. One of them (Jeff Thompson) was named a finalist for the APS LeRoy Apker award. The graduate students have presented talks at the APS March Meeting (Denver), CLEO/QELS (Baltimore), ICAP (Innsbruck) and the Caltech NEMS Summer School (Pasadena). Our group has also organized a program which brings Yale PI’s to speak at New England liberal arts colleges. The purpose of this program is to expose a broader range of undergraduates to cutting edge physics research. 30% Co-Funded by DMR 2008 Gordon Research Conference Mechanical Systems in the Quantum Regime February 17-22, 2008 Four Points Sheraton, Ventura Harbor, California Chairs: Jack Harris (Yale), Andrew Cleland (UCSB) Vice-chairs: David McClelland (ANU), Keith Schwab (Cornell) www.grc.org • Session topics (preliminary) • Cooling, feedback, control • Nonclassical states • Quantum limited measurements • Quantum vacuum effects • Quantum information processing • Interaction with quantum optics, atoms • Interaction with mesoscopic CM systems • Materials and fabrication techniques