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In this research, amplitude Fresnel zone plates (FZPs) were fabricated on fused silica glass with femtosecond laser. The focusing characteristics including focal length, diffraction efficiency, geometric concentrator ratio, spot energy uniformity, depth of focus and resolution were studied by simulations and experiments. To optimize the focusing characteristics of FZP, we proposed an optimized machining process, an extended FZP and an fractal FZP. The optimized machining process increased the diffraction efficiency of the amplitude FZP from 6.96% to 8.14%, the extended FZP broke through the limit of minimum line width in processing and improved the resolution, and the fractal FZP increased the focus depth from 4 mm to 10 mm. In addition, we wrote a FZP on the end face of multi mode fiber, the divergent annular beam converged and formed an focus ring at the focal plane. This research will provide broad applications in fiber tweezers, beam coupling and optical communication. [ABSTRACT FROM AUTHOR]

Femtosecond laser ablation is a flexible method for manufacturing gallium arsenide (GaAs) micro-optical components. However, its machining efficiency and surface quality do not satisfy industry requirements. Wet etching assisted femtosecond laser ablation is proposed to solve these problems. After corrosion, protrusions and particles are selectively corroded. X-ray diffraction and energy dispersive X-ray spectroscopy results show that oxides are formed after laser ablation, and the crystal cell size of GaAs increases. Thus the contact area between hydrofluoric acid atoms and the GaAs crystal cell increases, the ratio of modified-to-unmodified corrosion rate is as high as 10:1. A one-dimensional grating, a conventional Fresnel zone plate (FZP), and a fractal FZP are fabricated using this method. Experiments show that the GaAs micro-optical component can diffract and focus infrared light with a wavelength of 1.5 µm well. The process offers a way to achieve high efficiency and quality manufacturing of GaAs microstructures. [ABSTRACT FROM AUTHOR]