%0 Journal Article %J OPTICS EXPRESS %D 2013 %T Optomechanical and photothermal interactions in suspended photonic crystal membranes %A Woolf, David %A Hui, Pui-Chuen %A Iwase, Eiji %A Khan, Mughees %A Alejandro W. Rodriguez %A Deotare, Parag %A Bulu, Irfan %A Steven G. Johnson %A Federico Capasso %A Loncar, Marko %X We present here an optomechanical system fabricated with novel stress management techniques that allow us to suspend an ultrathin defect-free silicon photonic-crystal membrane above a Silicon-on-Insulator (SOI) substrate with a gap that is tunable to below 200 nm. Our devices are able to generate strong attractive and repulsive optical forces over a large surface area with simple in-and out-coupling and feature the strongest repulsive optomechanical coupling in any geometry to date (g(OM)/2 pi approximate to -65 GHz/nm). The interplay between the optomechanical and photo-thermal-mechanical dynamics is explored, and the latter is used to achieve cooling and amplification of the mechanical mode, demonstrating that our platform is well-suited for potential applications in low-power mass, force, and refractive-index sensing as well as optomechanical accelerometry. (C) 2013 Optical Society of America %B OPTICS EXPRESS %I OPTICAL SOC AMER %C 2010 MASSACHUSETTS AVE NW, WASHINGTON, DC 20036 USA %V 21 %P 7258-7275 %8 MAR 25 %G eng %N 6 %9 Article %R 10.1364/OE.21.007258