Optical devices and methods

An apparatus for generating vector vortex beams (VVB) that comprise non-uniform polarization states and orbital angular momentum (OAM), the apparatus comprising:

• a light source arranged to provide a source field;
• a polarization state generator, PSG, arranged to manipulate the source field to provide a modified field having a single polarization state;
• and
• a transformation module arranged to receive the modified field from the PSG and transform it to provide an output field, wherein the transformation module comprises a gradient-index, GRIN, lens and a spatially-variant half wave plate, SHWP, arranged between the GRIN lens and the PSG.

An apparatus for generating orbital angular momentum (OAM) beams that have uniform polarization states, the apparatus comprising:

• a light source arranged to provide a source field;
• a polarization state generator, PSG, arranged to manipulate the source field to provide a modified field having a single polarization state;
• a transformation module arranged to receive the modified field from the PSG and transform it to provide an output field, wherein the transformation module comprises a gradient-index, GRIN, lens;
• and
• a polarization state analyser, PSA, arranged to select a polarization state of the output field which is different from the polarization state of the modified field: