A module of a blue-violet laser diode and photodiodes for adaptive compensation of spherical-aberration

Much research and development has been reported for high-density optical disc systems using a blue-violet laser diode (LD) and a high numerical-aperture (NA) objective. The next phase is now underway - studying ways to mass produce them. We previously described adaptive compensation of spherical-aberration (SA) and a single-element objective, for overcoming the narrow tolerance of the substrate thickness error in high NA optics, and the narrow working distance of a conventional two-element objective, respectively. To facilitate their use in assembling a miniaturized optical pickup, we recently developed a module that integrates a blue-violet LD, photo-diodes (PD) and an etched mirror on a silicon substrate. For precise alignment of the module, we used the junction-down arrangement for the LD. We confirmed the ability of this blue-violet LD module to compensate for the SA and give good signal quality for the Blu-ray Disc format (23 GB).