Near-field optical head for disc mastering process

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 he formed almost at the inverse rare 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.