Programmable unitary spatial mode manipulation

J.-F. Morizur^1,2, L. Nicholls¹, P. Jian², S. Armstrong¹, N. Treps², B. Hage¹, M. Hsu³, W. Bowen³, J. Janousek¹, H.-A. Bachor¹

¹ Australian National University, ² Laboratoire Kastler Brossel

Journal of the Optical Society of America A 27, 2524 (2010).

Abstract: Free space propagation and conventional optical systems such as lenses and mirrors all perform spatial uni- tary transforms. However, the subset of transforms available through these conventional systems is limited in scope. We present here a unitary programmable mode converter (UPMC) capable of performing any spatial unitary transform of the light field. It is based on a succession of reflections on programmable deformable mir- rors and free space propagation.We first show theoretically that a UPMC without limitations on resources can perform perfectly any transform.We then build an experimental implementation of the UPMC and show that, even when limited to three reflections on an array of 12 pixels, the UPMC is capable of performing single mode tranforms with an efficiency greater than 80% for the first four modes of the transverse electromagnetic basis.