Optical back-action in silicon nanowire resonators: bolometric versus radiation pressure effects

We study optical back-action effects associated with confined electromagnetic modes in silicon nanowire resonators interacting with a laser beam used for interferometric read-out of the nanowire vibrations. Our analysis describes the resonance frequency shift produced in the nanowires by two different mechanisms: the temperature dependence of the nanowire's Young's modulus and the effect of radiation pressure. We find different regimes in which each effect dominates depending on the nanowire morphology and dimensions, resulting in either positive or negative frequency shifts. Our results also show that in some cases bolometric and radiation pressure effects can have opposite contributions so that their overall effect is greatly reduced. We conclude that Si nanowire resonators can be engineered for harnessing back-action effects for either optimizing frequency stability or exploiting dynamic phenomena such as parametric amplification.The authors acknowledge financial support from the Spanish Science Ministry through projects TEC2009-14517-C02-01/02, TEC2008-06756-C03-01 and CSD2010-00024 and from the EU through the project ERC-Starting Grants-StG-2011-278860-NANOFORCELLS. DR acknowledges financial support from the EU grant IOF-2009-254996.Peer reviewe