Laser drilling of superdeep micron holes in various materials with a programmable control of laser radiation parameters

The possibilities of enhancing the efficiency of laser drilling of micron holes, increasing their depth, and eliminating their conic shape are studied by using a single-mode loop Nd:YAG laser with self-phase conjugation on the gain gratings and passive Q-switching by a scanned gradiently coloured F₂^-:LiF crystal. Holes of diameters 15 – 150 μm and depth up to 20 mm with the aspect ratio (ratio of the hole depth to its diameter) of 50 – 155 are drilled in various metals and alloys. It is shown that passive Q-switch scanning during drilling provides the increase in the depth and speed of the laser drilling of superdeep holes by a factor of 1.5 – 2.