We propose to use femtosecond laser direct writing technique to realise dielectric optical elements from photo-resist materials for the generation of structured light from purely spin-orbital conversion transformations. This is illustrated by the fabrication and characterisation of spin-orbital optical angular momentum couplers generating optical vortices of topological charge from 1 to 20. The elements achieved using this techniques also were demonstrated its capabilities to working in the whole visible range with efficiency up to 85%. We also firstly demonstrated the abilities to combine the dynamic phase and geometric phase using the 3D fabrication capability of laser direct writing to create elements that generate different topological charges of optical vortices simultaneously with the shared aperture.
Proc. SPIE. 9142, Selected Papers from Conferences of the Photoelectronic Technology Committee of the Chinese Society of Astronautics: Optical Imaging, Remote Sensing, and Laser-Matter Interaction 2013
KEYWORDS: Optical transfer functions, Point spread functions, Imaging systems, Spatial frequencies, Image processing, Image restoration, Image resolution, Modulation transfer functions, Synthetic aperture imaging, Filtering (signal processing)
Due to the central obscuration problem exists in most optical synthetic aperture systems, it is necessary to analyze its effects on their image performance. Based on the incoherent diffraction limited imaging theory, a Golay-3 type synthetic aperture system was used to study the central obscuration effects on the point spread function (PSF) and the modulation transfer function (MTF). It was found that the central obscuration does not affect the width of the central peak of the PSF and the cutoff spatial frequency of the MTF, but attenuate the first sidelobe of the PSF and the midfrequency of the MTF. The imaging simulation of a Golay-3 type synthetic aperture system with central obscuration proved this conclusion. At last, a Wiener Filter restoration algorithm was used to restore the image of this system, the images were obviously better.