펨토초 레이저를 이용한 회절광학 소자 제작 및 광특성 평가

Abstract

Diffraction gratings with spatial periods of 2 mm and 5 mm have been fabricated by using a femtosecond laser which does not have limits in materials of micromachining and small thermal effects due to high peak power. We used a slowly moving scanning method with laser pulse synchronization with a stage moving speed. Diffraction angle and diffraction efficiency of those were measured. Simulation results of diffraction angle and diffraction efficiency of the diffraction grating calculated with the parameters such as line width, depth, and spatial period of the fabricated gratings were compared with experimental results measured with a He-Ne laser. Besides these, FZPs (Fresnel Zone Plate) with focal distances of 50 mm and 25 mm were fabricated and focal distances of fabricated FZP were measured. Those experimental results for diffraction gratings and FZPs match well with experimental results. Holograms were also fabricated and reconstructed by illuminating a reference beam with a wavelength of 543 nm, which reconstructed well designed characters in two dimension. These two dimensional characters in same plane will be extended to three dimensional plane and fabricated in the future.