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 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.