Cutting of Free Standing CVD Diamond Films by Optical Fibre Guided Nd:YAG Laser

Abstract

The performance of the Nd:YAG laser to cut thick (500 µm) free standing CVD diamond films for electronic, optical and mechanical applications, is investigated. A pulsed Nd:YAG laser at a wavelength of 1064 nm was employed. The cutting parameters varied within the following ranges: pulse energy = 0.8-4.6 J; pulse width = 0.3-1.0 ms; cutting speed = 5-10 mm•s -1 ; frequency = 100-500 Hz. The structural and morphological modification of the cutting surface was evaluated by optical and electron microscopy, and micro-Raman spectroscopy. A minimum energy density of 50 kJ•cm -3 is required to get complete cuts. The columnar morphology of the CVD diamond films leads to a high heat dissipation along the normal direction to the diamond surface. This effect allows a limited amorphized area, which allows cutting at high speeds up to 15 mm•s -1 . The best cutting configuration is to impinge the laser on the nucleation side of the freestanding plate, due to the favourable thermal conductivity gradient. The high flexibility of this type of laser, given by the possibility to guide the laser beam by means of an optical fibre allows the automation of the diamond cutting process.