Microstructuring of diamond bulk by IR femtosecond laser pulses

We report the fabrication of graphitic microstructures in the bulk of chemical vapor deposited (CVD) diamond using 120-fs laser pulses at 800-nm wavelength. The nature of the laser-modified region and generation of mechanical stresses in the surrounding diamond is studied with Raman spectroscopy. A spontaneous growth of the laser-modified region from the focal plane towards the laser has been visualized in the process of multipulse irradiation with different pulse energies. The formation of discrete or continuous graphitized structures is revealed depending on the varied local laser intensity. The physical processes governing the appearance of separate graphitic globules and continuous extension of the graphitized region are discussed. Controlling the laser irradiation conditions permits us to fabricate graphitic wires with typical length of 150 mu m and diameter of 1.5 mu m. The longer, 300-ps pulses, as applied to laser microstructuring of the CVD diamond bulk, are found to be inappropriate due to the stronger influence of structural defects on the damage threshold, the noticeable fluctuation of the structure diameter over the length and the pronounced cracking of the surrounding diamond.