Refractive elements for the measurement of the orbital angular momentum of a single photon.

We have developed a mode transformer comprising two custom refractive optical elements which convert orbital angular momentum states into transverse momentum states. This transformation allows for an efficient measurement of the orbital angular momentum content of an input light beam. We characterise the channel capacity of the system for 50 input modes, giving a maximum value of 3.

Measuring orbital angular momentum superpositions of light by mode transformation.

We recently reported on a method for measuring orbital angular momentum (OAM) states of light based on the transformation of helically phased beams to tilted plane waves [Phys. Rev. Lett.

Efficient sorting of orbital angular momentum states of light.

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.

Measuring optical vortices in a speckle pattern using a multi-pinhole interferometer.

We show that it is possible to find and characterise optical vortices in a speckle pattern using a multi-pinhole interferometer. This measurement does not require an interferometric setup, providing great experimental ease. In addition, a multi-pinhole interferometer can be made arbitrarily large and can therefore be adjusted to the expected speckle size.

Method for probing the orbital angular momentum of optical vortices in electromagnetic waves from astronomical objects.

We present an efficient method for probing the orbital angular momentum of optical vortices of arbitrary sizes. This method, based on a multipoint interferometer, has its most important application in measuring the orbital angular momentum of light from astronomical sources, opening the way to interesting new astrophysics. We demonstrate its viability by measuring the orbital angular momentum of Laguerre-Gaussian laser beams.