Dynamic copy window control in RF-MAMMOS readout

Coen A. Verschuren; Andre H. J. Immink; Martijn W. Blum

doi:10.1117/12.532415

16 September 2003 Dynamic copy window control in RF-MAMMOS readout

Coen A. Verschuren, Andre H. J. Immink, Martijn W. Blum

Proceedings Volume 5069, Optical Data Storage 2003; (2003) https://doi.org/10.1117/12.532415
Event: Optical Data Storage 2003, 2003, Vancouver, Canada

Abstract

RF-MAMMOS is a promising technology to reach storgae densities around 100 Gb/in². Using domain expansion (and collapse) driven by a small, external magnetic field, bits much smaller than the optical spot size can be read out with saturated signal levels. Because these bits are selected by the center of the thermal profile induced by the focused laser spot, it is essential that the readout conditions determining the size of this heated region, the copy window, are controlled very accurately. At the same time, the external field needs to be synchronized to the recorded data. This can be achieved by data dependent field switching: the external field starts in the expansion direction and is only modulated at the bit clock frequency when expansion for a mark is detected. In this way, each first peak of a mark run length contains complete timing information which is used as input for a phase locked loop (PLL). Based on this approach, a method is proposed to solve the readout margin problem. By applying a small, fixed modulation to the laser power or the external field at a frequency above the bandwidth of the PLL, we demonstrate that the induced timing modulation provides a suitable signal to actively control the size of the copy window. First experimental results confirm the feasibility of better than 1% power control accuracy, opening the way to robust readout at the highest densities.

Citation Download Citation

Coen A. Verschuren, Andre H. J. Immink, and Martijn W. Blum "Dynamic copy window control in RF-MAMMOS readout", Proc. SPIE 5069, Optical Data Storage 2003, (16 September 2003); https://doi.org/10.1117/12.532415

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