  In this paper we propose and experimentally demonstrate information transfer
through free-space using a laser beam encoded with multiple orthogonal
aberration modes in its phase profile. We use Zernike polynomials which forms a
complete set of basis functions to represent the aberration modes. The user
information is encoded as amplitudes of multiple Zernike modes whose linear
combination is used to define the wavefront of the laser beam in the
transmission station. It therefore requires a single phase modulating device
since the multiplexing is done digitally providing flexibility over the number
and type of modes used. The receiving station uses a wavefront sensor that
gives a direct measure of all the aberration modes from a single measurement
which is decoded to retrieve the user information. The transmission mechanism
enables the use of multiple modes and multiple strengths of each mode to encode
the user information and external perturbation compensation, utilizing the
completeness of the orthogonal modes.
