Rockstuhl, C.Salt, G.Herzig, H. P.2009-04-222009-04-222009-04-22200510.1364/JOSAA.22.000109https://infoscience.epfl.ch/handle/20.500.14299/37981We present our investigation of the torque exerted on dielectric elliptical cylinders by highly focused laser beams. The calculations are performed with rigorous diffraction theory, and the size-dependent torque is analyzed as a function of the axis ratio. It is found that highly elongated particles will experience a reversal of the torque for a radius that is approximately one third of the wavelength. This effect is attributed to interference effects inside the structure due to multiple reflections of the incoming wave. The evolution from a perfectly sinusoidal angular dependence of the torque to a more complicated pattern for increasing particle size is presented in detail. © 2005 Optical Society of America.text::journal::journal article::research article