Yoshihiko Matsuoka

Passively Q-switched Nd:YAG microchip laser over 1-MW peak output power for micro drilling

We report a palm top size passively Q-switched Nd:YAG microchip laser capable of producing lineally polarized 1.7-MW peak-power. This high-brightness laser enables to realize the efficient frequency doubling for micro drilling to stainless plates.

Characteristics of a laser beam spot focused by a binary diffractive axicon

Bessel beams formed by an axicon are nondiffracting beams. Such beams are used in the field of laser machining because they have several desirable characteristics, including a micron-sized focal spot and a deep focal depth. Conical lenses are generally employed for producing Bessel beams. A binary diffractive axicon was made by electron beam fabrication; the first-order diffracted beam from this axicon has a similar optical field to that of a refracted beam from a conical lens. The characteristics of a laser beam spot focused by the axicon were investigated. We demonstrated theoretically and experimentally that the peak intensity on the optical axis oscillated with a larger amplitude as the spot size decreased when the beam spot was observed in the vicinity of the axicon. This phenomenon was well explained by taking higher-order diffraction into account. We also investigated the wavelength dependence of the spot size focused by the axicon, and found that the spot size was constant.