Efficient sorting of orbital angular momentum states of light

Phys Rev Lett. 2010 Oct 8;105(15):153601. doi: 10.1103/PhysRevLett.105.153601. Epub 2010 Oct 4.


We present a method to efficiently sort orbital angular momentum (OAM) states of light using two static optical elements. The optical elements perform a Cartesian to log-polar coordinate transformation, converting the helically phased light beam corresponding to OAM states into a beam with a transverse phase gradient. A subsequent lens then focuses each input OAM state to a different lateral position. We demonstrate the concept experimentally by using two spatial light modulators to create the desired optical elements, applying it to the separation of eleven OAM states.