We explore the laser spot position (LSP) dependence of photothermal mode cooling in a microcantilever-based Fabry–Perot cavity. Experiments on photothermal cooling demonstrate that the direction of photothermal backaction on the first two cantilever modes is LSP dependent, which can be either parallel or antiparallel. A theoretical analysis of this LSP-dependent effect identifies the parallel and the antiparallel coupling regions along the lever. Simulation results are in quantitative agreement with our experimental observations. We conclude that the cooling limit imposed by photothermal mode coupling can be surmounted by operating in the parallel coupling region.
© 2012 Optical Society of America
Instrumentation, Measurement, and Metrology
Original Manuscript: November 18, 2011
Revised Manuscript: December 15, 2011
Manuscript Accepted: December 15, 2011
Published: February 9, 2012
Hao Fu, Cunding Liu, Yong Liu, Jiaru Chu, and Gengyu Cao, "Laser spot position dependence in photothermal mode cooling of a microcantilever," Opt. Lett. 37, 584-586 (2012)