Multi-functional Micro-column Lens Characteristics

Optics has been experienced long and zigzag developments in the last several centuries since its birth. Traditional optical elements such as lenses and prisms are based on refractive and reflective principle. Their feature sizes are always much larger than the wavelength of light, so that we can apply scalar diffraction theory which is based on the Fresnel-Kirchhoff diffraction formula to analyze the properties of them. After 1960's, with the invention of laser and the advance of optical lithography in recent years, optical elements gradually become smaller and smaller with higher efficiency. It also tends to be integrated. When the feature size of micro-optical element becomes comparable with or smaller than the light wavelength, the scattering effects become prominent. In this case the vector diffraction properties in optics should be taken into account; the scalar diffraction theory is no longer valid now and it requires the vector diffraction theory for designing, analyzing, and evaluating the performances of micro structure optical elements. In this thesis we design the profile of micro-cylindrical axilens to realize the long common focal extended depth and study the characteristics of several kinds of micro-cylindrical axilens based on rigorous electromagnetic theory and boundary element method with the help of boundary conditions of electromagnetic fields and Sommerfeld radiation conditions. The achievements of the studies are summarized below:1. The common focusing characteristics of cylindrical microlens with a long focal depth under the given multiple wavelength illumination are analyzed based on Boundary Element Method (BEM). The surface-relief profile of finite-substrate-thickness microlens having a long focal depth is presented. Its focusing performances, such as the common extended focal depth (CEFD), the spot size, and the diffraction efficiency are numerically studied in the case of the TE polarization. Two modified profiles of finite-substrate-thickness cylindrical microlens are proposed for enlarging the CEFD. The rigorous numerical results indicate that the modified surface-relief structures of cylindrical microlens can successfully modulate the optical field distribution to achieve longer CEFD, higher transverse resolution, and higher diffraction efficiency simultaneously。...