Laser Irradiation Responses of a Single-Crystal Diamond Produced by Different Crystal Growth Methods

Abstract

Abstract:Responses of two types of single-crystal diamonds, prepared by chemical vapour deposition (CVD) and high pressure high temperature synthesis (HPHT) methods, respectively, to a nanosecond pulsed neodymium-doped yttrium aluminium garnet (Nd:YAG) laser were investigated and compared. It was found that due to the difference in the transmission rate and refractive index, the laser-induced surface/subsurface features of the two types of samples were distinctly different. For the CVD sample, destructive interference takes place on the upper surface, leading to direct ablation of smooth grooves with deposition of graphite. For the HPHT sample, however, laser-induced grooves were formed on the reverse side of the irradiation surface (namely, the lower surface) at certain laser fluences due to the constructive interference phenomenon of the laser and the high refractive index of the material. The reverse-side irradiation resulted in the formation of deep and sharp grooves with rough bottoms and insignificant deposition of graphite on the area surrounding the groove. The machining thresholds for the upper and lower surfaces of both types of diamonds were experimentally obtained and theoretically verified. The findings of this study provide important process criteria for laser machining of different kinds of diamonds. The reverse-side irradiation method enables efficient machining of deep grooves in diamonds using a lower power laser.

High surface quality micro machining of monocrystalline diamond by picosecond pulsed laser

“…When the liner polarized laser beam was used by changing the optical setup, the generating direction of these periodic surface structures was still in parallel direction to laser scanning line regardless of polarization plane, and it appeared only after the generation of groove with a certain depth. Thus, these phenomena were caused by reflection of laser beam on the wall of groove, as reported by using nanosecond pulsed laser [7]. On the other hand, unique processing phenomenon could be observed only at 500 shots and 1000 shots.…”

“…Although diamond has high optical transparency for a laser beam, stable absorption of laser energy can be achieved by high peak power of pulsed operation, which ignites multi-photon ionization and absorption of laser beam at defects in diamond. Diamond is usually removed by the combination of ablation phenomena, graphitization and oxidization [7]. However, graphited or carbide layers remain as heat affected zone after removal process by nanosecond pulsed lasers [8,9].…”

Energy beam-based direct and assisted polishing techniques for diamond: A review

“…Over the recent years, numerous lasers have been used for diamond processing, including pulsed excimer [136], Nd-YAG [137], XeCl [138], and ArF [139] lasers. Short-pulse lasers are especially effective in achieving high-precision and sharp profiles while minimizing heat conduction into the bulk material [140]. Femtosecond pulses and an accelerating beam can be used to achieve curved profiles with micron-sized curvatures.…”

High-quality micro-shape fabrication of monocrystalline diamond by nanosecond pulsed laser and acid cleaning

“…The removal process of monocrystalline diamond by the nanosecond pulsed laser was also discussed, and some researchers reported that there was smooth surface at the bottom of V-shaped micro-grooves [10,11]. However, the smooth area is limited to the tip of the micro-groove, and a flat surface could not be obtained for a wide area.…”