Axially symmetric on-axis flat-top beam

A synthesis method for arbitrary on-axis intensity distributions from axially symmetric fields is developed in the paraxial approximation. As an important consequence, a new pseudo-nondiffracting beam, the axially symmetric on-axis flat-top beam (AFTB), is given by an integral transform form. This AFTB is completely determined by three simple parameters: the central spatial frequency S-c, the on-axis flat-top length L, and the on-axis central position z(c). When LSc much greater than 1, this AFTB can give a nearly flat-top intensity distribution on the propagation axis. In particular, this AFTB approaches the nondiffracting zero-order Bessel J(0) beam when L --> infinity. It is revealed that the superposition of multiple AFTB fields can give multiple on-axis flat-top intensity regions when some appropriate conditions are satisfied. (C) 2000 Optical Society of America [S0740-3232(00)01202-3].