Diffractive Optics Design

Doctoral thesis, 1997

Diffractive optical elements (kinoforms) change the way light propagates, and can perform very complex tasks. They can split an incident beam into any number of outgoing, and possibly focused, beams (fan-out). Other kinoforms shape the cross sectional intensity distribution of the beam, which is often Gaussian, into a rectangle with constant intensity, for instance. What function the kinoform implements depends on the surface relief etched on the kinoform. This work considers important aspects of the design of diffractive optical elements, within the scalar optics approximation, such as - efficient optimization of the kinoform relief with the optimal-rotation-angle method. For example, shallow, phase-swing restricted kinoforms are designed. - non-diffraction-limited (beam shaping) design. One experimental example is a semiconductor laser beam shaping system consisting only of a multiple-function kinoform. - finding a model for the effects of fabrication on the relief (the proximity effect) and trying to compensate for this effect already in the design, which can yield very uniform fan-out patterns even when the proximity effect is considerable. - integrating diffractive optics with semiconductor optics. Examples are kinoforms illuminated by VCSELs and dislocated binary gratings that outcouple a guided wave and also impose a continuous phase modulation on the outcoupled wave. - using the exact (no Fresnel approximation, for instance) scalar theory, based on the scalar wave (Helmholtz) equation, in an efficient formulation that enables the design of kinoforms producing virtually any desired, three-dimensional, fan-out light distribution.