Numerical Aperture-Dependent Spatial Scaling of Plasma Channels in HPHT Diamond

Abstract

The investigation of plasma channels induced by focused ultra-short 1030-nm laser pulses in bulk of synthetic High Pressure High Temperature (HPHT) diamond revealed strong dependence of their spatial parameters on the used numerical aperture of the lens (NA = 0.15–0.45). It was shown that at weak focusing conditions it is possible to significantly increase the length of the plasma channel with a slight increase in pulse power, while tight focusing allows one to obtain more compact structures in the same range of used powers. Such a dependence paves the way to new possibilities in 3D processing of transparent dielectrics, allowing one, for example, to vary the spatial parameters of modified regions without changing the setup, but only by controlling the lens aperture, which seems very promising for industrial applications.