Error analysis and alignment in the optical head of near field recording system

Abstract

In this paper, error analysis and alignment for the optical head of Near Field Recording (NFR) system are presented. Using optical systems analysis tool -CODEV, the NFR system are designed. After design, we fabricate the NFR system and test the reading & writing performance of the NFR system. The test results show that the reading & writing performance is not good enough. In order to find the cause of the performance drop in the NFR system, assembly tolerances of the optical head of NFR system are simulated. The simulation results show that the tolerance in the optical head of the NFR system is very tight. So in order to align the optical head within the tolerance limit, we design and fabricate an alignment system which can detect the RMS wavefront aberration and align the optical head. Before the experiment, we model the interferometer (by CODEV) and analyze the interference pattern trend. The interference patterns will be compared with the experiment results. The system can control the position of optical head of the NFR system using the pico-motor actuators and the capacitance type gap sensors. Using the system, we can align the objective lens and the solid immersion lens in 5-axis. Finally, we verify the alignment performance of the optical head using the alignment system. We can align the optical head within tolerance limit using the proposed system.