Papers by Author: Yasuhiro Kunieda

Abstract: A Nd:YAG crystal having a special structure achieved laser operation with an extinction ratio of over 20 dB, a CW (continuous wave) average power of 6 W, a pulse width of 50 ns, and repetition rates in the range 1 kHz – 10 kHz for an output wavelength of 1064 nm for effectively cooling the crystal for the case of laser dressing. The birefringence induced by the stress applied to the crystal results in the production of elliptical polarization before the Brewster-window and thus decreases the laser efficiency. In this paper, we analyzed the relationship between the distortion and the birefringence in a Nd:YAG crystal and the resulting effect on the laser power.

Abstract: A completely new diamond wheel, named the 3R wheel, has been developed. The 3R wheel has three unprecedented functions, reconfiguration, restoration and recyclability, and is molded from a mixture of special thermoplastic resin filler and diamond powder. The concept of the 3R wheel is to control the quantity and the position of abrasive material by actively using heat. In this study, tungsten carbide (WC) was ground using a thermoplastic resin bonded diamond wheels (radius 1.4 mm) with three different concentrations of 1500 grain size abrasive. As a result, a grinding ratio of over 200 and 18 nmRa roughness was achieved without dressing. In addition, a large quantity of abrasives was confirmed on the wheel surface by observation.

Abstract: This paper reports a new laser conditioning method for micro-wheels with ultra-fine grit diamond, which are used for the micro grinding of micro-aspherical optics. Resinoid-bonded micro-wheels with ultra-fine grit diamonds are used for micro grinding. Such small wheels have the problem of poor ground surface roughness due to their few effective cutting edges and low peripheral speeds. In the present work, new truing and dressing methods are proposed to produce many effective cutting edges. The new method uses the third harmonic of a Nd:YAG laser, which is suitable for processing resinoid bond material. It was found that a SD1500B wheel treated using the new method had a higher cutting edge density than one treated using a conventional method, the cup truer method. A good surface roughness was obtained using the new method.

Abstract: The state of the wheel surface after dressing is important for processing of a surface to the nano-order level. A laser dresser was developed using ultraviolet (UV) laser light, which imparts no mechanical damage to the resin bond. One feature of this system is that UV laser energy is transmitted by a special optical fiber for UV light, and is transmitted only to the resin bond. Using this newly developed laser dresser, it was possible to ablate the resin bond to a depth of over 2 microns using a fiber with a core diameter of 200 microns.