Fully complex diffractive optics by means of patterned diffuser arrays: Encoding concept and implications for fabrication

Arbitrary complex-valued functions can be implemented as arrays of individually specified diffusers. For any diffuser, only average step height and vertical roughness are needed to control phase and amplitude. This modulation concept suggests potentially low-cost fabrication methods in which desired topographies are patterned by exposing photoresist with partially developed speckle patterns. Analyses and experimental demonstrations that illustrate the modulation concept and aspects of the fabrication method are presented, with particular emphasis on limitations of complex recording set by various photoresist and exposure properties. Applications of diffuser array concepts to spatial light modulators and to gray-scale lithographic printing of micro-optics are also mentioned. (C) 1997 Optical Society of America.