Remote lensless focusing of a light beam

Understand

Remote focusing of light in a graded-index medium via mode interference is demonstrated using exact analytical solutions of the wave equation.

• Strong focusing of light occurs at extremely long distances and it revivals periodically with distance due to mode interference.
• High efficiency transfer of a strongly focused subwavelength spot through optical waveguide over large distances takes place with a period of revival.
• Super-oscillatory hot-spots with the sizes which are beyond the conventional Abbe diffraction limit can be observed at large distances from the source.