Tetsuo Andou

High Storage Density Optical Recording with a Stable Micro Green Second Harmonic Generation Laser Consisting of Nd:YVO4 and KTP

A stable micro second harmonic generation (SHG) laser consisting of a diode- pumped Nd:YVO4 laser doubled by KTiOPO4 achieves 3 times higher storage density than usual on an erasable optical disk.

Diffraction-limited collimation optics for a channel waveguide Cerenkov frequency doubler for diode lasers

Optical path analysis applying diffraction theory and geometrical ray tracing, and with collimation experiments shows that a hemiconic lens can convert the arc of blue radiation formed by Cerenkov second-harmonic generation to a parallel plane wave. To obtain an aberration-free plane wave, we modified the apex angle of the cone according to the birefringence of the waveguide. To correct chromatic aberration, we needed to have diode laser wavelength tuning with the aid of an achromatic cone lens doublet.

257-nm optical disk cutting-machine

Many formats have been proposed and examined for next-generation DVD with a capacity of over 25 GB. Disk mastering is necessary for this purpose, and optical disk cutting-machines are key equipment for disk mastering. The laser wavelengths used in cutting-machines are getting shorter as the density of disk memory increases, and these wavelengths are shifting to the deep-UV (ultra-violet) range. We developed a 257-nm cutting-machine with an automatic realignment system for the laser beam and an effective AF (auto-focus) system for a non-dual wavelength objective lens. A 200 mW Ar-SHG laser is used as the laser source. The automatic realignment system consists of two sets of beam-position detectors and mirror actuators, and it is placed after the laser. An EOM (electric-optical modulator) is used as a noise-eater for each line, and a spatial filter is placed between AOM (acoustic-optical modulator) and AOD (acoustic-optical deflector) for wave-front correction.

Development of nonlinear crystals and violet-blue SHG laser

Compact solid-state blue laser have great potential for use in optical data storage, laser beam printing, particle countering, reprographics, holography, and fluorescent bioanalysis. We report recent progresses in qualities of LiB3O5 and K3Li2 (TaxNb1-x)5O15 nonlinear crystal which are essential in manufacturing bulk-type blue SHG devices. We also review newly developed violet-blue laser, 20 mW output, using intracavity frequency doubling of a diode laser pumped Cr:LiSrAlF6 laser with low loss LiB3O5 crystal as a frequency doubler.