Focal shift and focal switch of phase-lock partially coherent flat-topped array beams passing through an aligned and misaligned lens system with aperture

The focal shift and focal switch of phase-lock partially coherent flat-topped (PCFT) array beams passing through a lens system with aperture is studied in detail. It is shown that there is a focal shift for mention beam propagating through aligned optical system and the amount of the focal shift depend on optical system and beam characteristics. In addition, a new phenomenon called focal switch occurs for misaligned optical system, i.e. the focal shift experiences a sudden transition as the aligned optical system turns to misalign one. It is shown that, the necessary conditions for the focal switch to take place are also investigated.

► The result show that the focal shift experiences a sudden transition as the aligned optical system approached to misaligned one. ► The focal switch occurs for any value of flat-topped order, radius aperture and distance between the neighboring centers. ► We investigated the necessary conditions to appear of focal switch.