Abstract
We present a proof of concept for a vector beam polarization state spectrum analyzer based on the combination of a polarization diffraction grating (PDG) and an encoded harmonic q-plate grating (QPG). As a result, a two-dimensional polarization diffraction grating is formed that generates six different q-plate channels with topological charges from −3 to +3 in the horizontal direction, and each is split in the vertical direction into the six polarization channels at the cardinal points of the corresponding higher-order Poincaré sphere. Consequently, 36 different channels are generated in parallel. This special polarization diffractive element is experimentally demonstrated using a single phase-only spatial light modulator in a reflective optical architecture. Finally, we show that this system can be used as a vector beam polarization state spectrum analyzer, where both the topological charge and the state of polarization of an input vector beam can be simultaneously determined in a single experiment. We expect that these results would be useful for applications in optical communications.
Highlights
In recent years there has been a very intense research activity in the development of communication systems based on multiplexing of vortex beams having angular orbital momentum (OAM)[1]
We combine the two gratings presented in the previous subsections: we combine the multiple q-plate grating diffracting in the horizontal direction, with the polarization grating diffracting in the vertical direction
Our detector array does not have sufficient resolution to accurately measure the strengths of the delta functions. Such precise higher-order polarimetric measurements would require better resolution both in the detector, and in the spatial light modulators (SLM) encoding the grating. These results demonstrate the experimental realization of a vector beam polarization diffraction grating capable to generate, in a single shot, an array of vector beams with different topological charges and different states of polarization
Summary
In recent years there has been a very intense research activity in the development of communication systems based on multiplexing of vortex beams having angular orbital momentum (OAM)[1]. They have been demonstrated in fibers[2], and in free space[3, 4]. In attempts to increase the information content in optical communication systems, researchers have been investigating vector beams[18] These beams are characterized by a two dimensional polarization state pattern that depends on both the charge (OAM) of the generating device and the polarization state encoded onto the beam. The flexibility provided by SLMs allows the generation of arbitrary q-plates
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