Amplitude, phase and polarization are essential parameters of an optical field. In the past decade, with the enhancement of techniques in manipulating phase and polarization states in complex optical fields, optical vortices and vector beams are investigated in a closely coupled fashion in terms of efficient beam generation and manipulation, stable transmission and novel detection aimed at various applications. In this special issue 6 invited papers demonstrate a number of typical topics in the field, with emphasis on the vectorial beam generation and optical communication systems utilising orbital angular momentum (OAM).

The energy storage of solar radiation with magnesium as an energy reservoir is proposed for renewable energy cycle. Magnesium reaction with water generating hydrogen and residual MgO is used to retrieve energy. Solar pumped laser is used to reduce MgO back to magnesium. This unique reduction process is possible because highly concentrating power density of laser radiation realizes non-equilibrium states of magnesium and oxygen dissociation from MgO and quickly separates each other for avoiding recombination to MgO. The proposed energy cycle consists of three key technologies: power generation by magnesium combustion, reduction of magnesium oxide, MgO, the combustion residue, and solar pumped laser that drives the MgO reduction process. This paper describes the experimental investigation of Mg combustion engine characterization.