High-efficiency production of propagation-invariant spot arrays

Tailoring of the transverse intensity profiles of propagation-invariant opt ical fields is considered. The design of diffractive elements capable of re alizing such fields by Fourier synthesis is discussed. High-efficiency real ization of finite-aperture approximations of the constructed fields is demo nstrated in a system consisting of two multilevel diffractive elements. The first element is a diffractive toroidal lens, which focuses the incident f ield into a ring pattern. The second diffractive element, located at the fo cal plane of the first element, introduces the phase modulation necessary t o realize the desired transverse intensity profile behind a separate collim ating lens. The influence of the fabrication errors of the diffractive elem ents on the fidelity of the propagation-invariant spot array is simulated, and system-integration aspects based on substrate-mode planar-integrated op tics are considered. (C) 2000 Optical Society of America [S0740-3232(91)005 01-X] OCIS codes: 050.1970, 260.1960, 070.2580.