Improved Air-Gap Control for SIL-Based Near-Field Recording System

We propose a gap servo method to reduce the overshoot in the near-field (NF) region. In general, we use a mode-switching servo which consists of approach, hand-over, and gap-control modes. However, there is a critical problem, such as an overshoot at the turning point from the approach mode to the hand-over mode, which may cause a collision between the SIL and the disk. In this paper, we propose an improved NF gap servo system using an exponential input in the approach mode which can reduce the overshoot and settling time of the mode-switching servo