Design And Analysis Of Multifunction Diffractive Optical Elements

Diffractive optical element (DOE) has been widely used in various optical systems because of its many advantages. DOE becomes the first choice for optical communication, correlation filtering, wavelength-division multiplexing, and so on. It's interesting to investigate and design the DOE for achieving multifunctional optical properties.This thesis aims to design a multi-function DOE for implementing spectral synthesizing and spatial dumultiplexing simultaneously. At the same time, we study the focusing characteristics by a microlens with long focal depth plus a variable π-plate, and achieve a hollow beams by adjusting the appropriate parameter. The hollow beam can be used to be optical tweezers, which can control and operate atoms or micro- or nano-particles in various areas. The content of this thesis are as follow:(1) We view the history of diffractive optics and give a brief introduction about DOE's advantages and applications in various fields.(2) We revisit theories of diffractive optics including scalar diffraction theoretical method and vector diffraction theoretical method. Some optimization algorithms are described.(3) DOEs are designed for implementing spatial demultiplexing and spectral synthesizing simultaneously by using conjugate gradient optimization algorithm. Three different design cases for the spectrum window of the optical communication: three discrete spectral segments in one direction, two discrete spectral segments in two directions, and three discrete spectral segments in three directions, are implemented. The numerical simulations indicate that the designed multi-functional DOEs can successfully generate desired spectra at predesigned directions. These designs can provide a useful information for designing the wavelength division multiplexer and the arrayed waveguide grating in various optical systems.(4) We investigate the focusing properties of Gaussian beams diffracted by a variable π -plate plus lens with long focal depth, and analyze the dependence of the diffracted focal light field on the variable π -plate clinging tightly to the multifunctional lens and on the preset long focal depth of the lens. We calculate the results, which show the changes of the system's optical behavior, with three different equations of long focal depth. In a word, DOEs have more advantages compared with the traditional optical element. Designing and manufacturing DOE to realize multi-functions is necessary.