Abstract

Scalar diffraction theory is widely used to design and analyze diffractive optical elements. This approach has been the approach of choice for it is easy to use, lacks computation strain, and more importantly, offer some direct approach for the design of diffractive elements. The validity and, therefore, the usability of the scalar diffraction approaches are based on the assumption that the smallest feature in the diffractive element is much greater than the wavelength of incident light. However, recent advances in the fabrication techniques have resulted in producing diffractive optical elements with small feature sizes of wavelength and subwavelength dimensions and scalar diffraction approaches may not be applicable. Rigorous diffraction analysis techniques have been developed and/or refined to analyze these wavelength size structures. These methods include rigorous coupled-wave theory, modal approach, method of moments, and other differential and integral methods. These electromagnetic theory based approaches provide powerful, accurate, and relatively efficient analysis methods. However, they do not provide satisfactory tools for the systematic design of diffraction elements.

© 1998 Optical Society of America