Design Of Filter To Optimize Optical Field Construction Of Near-Field Optical Storage System With A Solid Immension Lens

Along with the information and knowledge's explosive growth, it is endless for us in pursuing high-density data storage. The optical storage technology, which takes optical disk as a carrier of information in today's world, is a necessary way of the information storage. Nowadays, near-field optical solid immersion lens storage is a powerful competitor of improving data storage density now.In order to decrease the spot size and improve the focal depth, a filter, which can optimize optical field distribution, is generally inserted in near-field solid immersion lens optical storage system For example, a two-zone phase filter and a two-zone amplitude filter can decrease the spot size, but the side-lobe intensity wasn't suppressed; a five-zone amplitude filter extends the focal depth, but the side-lobe also wasn't suppressed; three-zone amplitude filter with a low side-lobe intensity was demonstrated to extend focal depth and decrease spot size, but the central peak was very low; a three-zone binary phase filter was designed to extend the focal depth with a high central peak, but the spot size was not decreased. In this foundation, on basis of vector diffractive theory a five-zone amplitude-phase hybrid filter and a five-zone binary phase filter are designed based on the MATLAB optimization toolbox to optimize the optical field distribution. Compared with no filter, the two filters can obviously extend the focal depth with a lower side-lobe intensity and a high central peak while the spot size isn't increased. They can also decrease the spot size and keep the central peak high when the side-lobe intensity is suppressed. Then the three-zone ternary phase filter is designed to decrease the spot size and increase the focal depth. When the central spot intensity drops to 0.8 times of the case without any filters and the side-lobe is suppressed to 0.1 times of the central peak, the spot size is decreased by a factor of 21%. At the same time the side-lobe within a low level and the spot size maintaining constant with the case of no filter, the focal depth is increased by a factor of 1.6 when the central peak is reduced by a factor of 0.5. Meanwhile, compared with the three-zone binary phase filter, the three-zone ternary phase filter has superior characteristic in whether decreasing the spot size or increasing the focal depth.