Study On Spiral Phase Plates And Its Applications In Optical Information Processing

A spiral phase plate (SPP) is an optical element with an optical thickness that increases with the azimuthal angle so that an incident plane wave emerges with a helical phase front. As a novel diffraction optical element, SPP has played an important role in many regions, such as optical information processing, optics micro-manipulation, biomedical physics, topography measurement and astronomical observation. In this thesis, we explored the applications of SPP in optical information processing as a novel spatial filter, which performing radial Hilbert transform, generating optical vortices, spiral phase contrast imaging and phase-shifting digital holography. The major content and results are as follows:1. We described the structure and types of SPP, and introduced the development of SPP research and its applications.2. We made a description of diffraction theory of SPP, and analyzed the optical vortex diffraction properties of SPP. We also introduced some methods to achieve spiral phase transform, such as using a liquid crystal spatial light modulator, coherent computer generated holograms and phase holograms.3. We analyzed the theory of spiral phase contrast imaging system and its characteristics, and introduced the applications of SPP in optical information which consist of performing radial Hilbert transform, generating optical vortices with arbitrary shape and array and spiral phase contrast imaging. Furthermore, we verified the spiral phase contrast imaging method by digital simulation.4. On the basis of the properties of spiral phase filter, we presented a new phase-shifting digital holography, i.e., common path phase-shifting digital holography system based on a spiral phase filtering. This technique uses a spiral phase plate with a small central aperture placed on the Fourier plane of an imaging system. If the spiral phase filter is rotated by a certain angle around its central axis, a phase shift between the zero-order spatial frequency component and the remaining of the object is produced, and the magnitude of this phase shift is proportional to the rotation angle. Using this property, we can record a sequence of intensity distribution of the output beams corresponding to different rotation angles, and then digitally reconstruct the pure phase or complex-amplitude objects by using a phase-shifting algorithm. Both the theoretical analysis and simulation experiment results demonstrate the feasibility of this approach.