Design And Fabrication Research Of Diffractive Micro-Optics Structures For Broad Wavelength Range

In this thesis, the principle diffractive objective lenses for Red-Laser-High-Definition storage system and the diffractive micro-optics structures for controlling wavefront transmission in infrared and THz wavelength range, are designed and fabricated based on the complex diffractive micro-optics theory. Both the intensity or amplitude and the phase of light wave out from the devices mentioned above, can be processed efficiently. The fabricated diffractive objective lens will be used in the next generation of Red-Laser-High-Definition storage system. The basic requirements for diffractive objective lens include: having 3mm focal length and then focusing red incident beam into a very small focal spot of 0.5μm diameter. The diffractive micro-optics structures can be used to generate several wavefronts for simulation the light field in atmospheric turbulence so as to valuate the imaging efficiency of adaptive optical system.Based on the planar wave scalar angular spectrum diffraction theory, several diffractive optical elements, which are similar to that designed by the strict electromagnetic wave theory, are designed. Compared to common method, the current design processes are easier and then the processed data is fairly small. The iterative angular algorithm is constructed through combining the angular spectrum diffraction theory with the Gerchberg-Saxton (GS) algorithm, which is one of the traditional methods for designing diffractive optical elements. The new algorithm has been used to design the diffractive objective lens and then the diffractive wavefront structures by controlling both the light intensity and phase, simultaneously. Numerical simulation shows that the designed results already meet the requirements to diffractive elements.The method for fabrication diffractive elements in this thesis is only consist of single mask photolithography, so as to completely eliminate the traditional multistep photolithography processes and therefore improve the fabrication precision, remarkably. The rational mask layouts are selected according to the feature size and the phase map of diffractive elements. For diffractive objective lens, a single step electron beam photolithography has been used so as to meet the fineness requirements of micro-nano-structures formed over the surface of silicon wafer. The same single step photolithography has also been used to fabricate the diffractive micro-optics structures with large feather size. In the etching process, the low cost wet KOH etching is employed to achieve the fabrication of devices. Surface morphology and optical performance test of the fabricated diffractive elements show that desired fine microstructure patterns are formed efficiently over the surface of silicon wafer, and then their surface roughness has reached the optical mirror level. The constructed theory and obtained experiments will highlight further applications.