Japanese scientists from the AIST institute are working on a true 3D display. From DailyTech ->”The display does not rely on any sort of optical illusion or disorientation. Instead, infrared lasers are aligned to converge and create small amounts of plasma. The plasma acts as a floating “dot” on top of the laser grid.” Creating the amazing effect which is 3D display. Really looking like a StarTrek technology.
It seems that the device needs a vapor source with specific electron/ion content in order to generate the dots.