Abstract
The fabrication of diamond-based optical elements for high-power CO2 lasers is of particular interest because of low optical absorption, high thermal conductivity and weak temperature dependence of the refractive index of diamond [1]. However, the use of high-quality CVD diamond plates in this field is limited by substantial Fresnel-reflection losses (about 30%) and small thickness (up to 1-2 mm) which restricts an aperture of a classical optical element. In [2,3], a technology of diamond film surface antireflective structuring using the selective ablation of the surface of the diamond-like substrate by the excimer UV laser light is discussed. In [4,5], a technology of UV laser ablation has been successfully applied for manufacturing the diffractive lens micro- relief. In [6,7], the manufactured diamond diffractive optical elements (DOEs) to focus the CO2 laser light are studied experimentally and the results are discussed. However, the technology described in [4-7] does not allow the micro- relief to be generated with a feature size less than 10-20 μm2, which certainly decreases the potential fields of the technology application. For instance, it would be difficult or impossible to use such technology for wavelength less than 10.6 microns. In this paper, we look into the possibility of generating a micro-relief on the diamond substrate using ion-chemical and plasma-chemical etching technologies. In [8] we presented first results of ion-chemical etching technology application for diffractive grating formation on the surface of diamond film. Later, in [9] results of diamond micro-lenses and sub-wavelength antireflection structures formation by plasma etching were presented. In the present paper, we continue investigation of grating formation on the diamond surface by plasma and ion etching.