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Real-Time Focal Spot Profiling for the Adjustment of the Focus in Near Field Recording System

The tolerance of the optical components in the near-field recording (NFR) system is analyzed. The system uses a solid immersion lens (SIL) for near-field recording and an air bearing slider to maintain the near-field gap between the SIL and a magneto-optic (MO) disk. From the analysis, it is found that some of the components have a sub-micrometer level tolerance, which is unsuitable for practical application. To loosen this tight tolerance, the position of the collimator lens (CL) is adjusted according to the assembly state. The state of the assembly is detected in real time from the intensity-profile signal that is generated through a developed technique. Therefore, by monitoring the signal carries out the adjustment of the CL. The performance of the technique is evaluated through numerical calculation and the experiment is carried out in the developed NFR system.