UV laser polishing of thick diamond films for IR windows

Diamond has very suitable properties for infrared IR. window applications. The rugged surface of a free-standing 320 mm thick diamond film grown by chemical vapour deposition CVD.is polished with the UV light of an ArF excimer laser ls193 nm.. The angle of incidence is 858 and irradiation is subsequently performed at three planar directions around the perpendicular axis. Scanning electron microscopy SEM.is used to visualise the surface before and after the polishing procedure. With a profilometer tip radius 5 mm.the improvement of the average roughness of the surface is measured. Polishing is analysed in dependence on the size of surface irregularities by means of fast Fourier transformation FFT.of the signal of the profilometer. Surface roughness measurements are also performed on the polished surface with an atomic force microscope AFM.. With IR transmittance measurements the optical quality is analysed over a wavelength range of 2.5 to 25 mm before and after polishing. The oxidative removal of the laser induced graphitic layer is studied with optical spectroscopy techniques. q1999 Elsevier Science B.V. All rights reserved