Nondiffracting optical fields: some remarks on their analysis and synthesis

Recently Durnin pointed out the existence of nondiffracting beams that propagate in free space with their energy confined around their axis but that experience no spread or divergence J. Opt. Soc. Am. A4, 651 ( 1987). This Communication provides an alternative way of interpreting these results. The approach is based on the McCutchen theorem from which the necessary conditions for a nondiffracting field are derived. This description may be useful in suggesting several different means of synthesizing such fields and in providing a convenient way of estimating their practical limitations. Some examples, inspired by known techniques studied for depth of field enhancement, are briefly mentioned.