Near-field recording for the disc mastering process was realized. A high-numerical-aperture (NA)
objective (NA=1.4) composed of an aspherical lens and a solid immersion lens (SIL) was driven by an
air pad and a piezotransducer. The gap between the SIL and the glassmaster was controlled by a new
gap detection method using the totally internally reflected beam from the bottom surface of the SIL. In
the near-field operation, the gap was maintained at 100 nm with a residual error of ±4.8 nm. In the DC
exposure with a laser beam of 413 nm, a narrower groove structure could be formed almost at the
inverse rate of NA expansion. In the read-only memory (ROM) exposure with an eight to fourteen
modulation plus (EFM+) signal, signal bottom jitter values of 9.8% for an 18 GB disc and 10.9% for a
20 GB disc were obtained.
Using Blu‐ray disc technology in which the focus servo‐system and the energy servo‐system are mounted on one head, we can precisely control the scanning beam and thus the location of the grain boundaries generated by the scanning beam.
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