Frequency doubled Nd:YAG laser with high average power in processing of ceramics, metals and composites

Abstract

This paper describes the use of 532 nm green light generated via frequency doubling or Second Harmonic Generation (SHG) of a continuously pumped and acusto-optically, AO- Q-switched, and a passively Q-switched Nd:YAG laser using KTP and LBO crystals. The resulting pulse energies were lower than at the fundamental wavelength but parameters such as pulse duration and pulse repetition frequency (PRF) remained the same. The better focusability of the green light compensates for the losses during frequency conversion when used for drilling.The SHG laser beam was successfully used for drilling and cutting hard to machine ceramics (e.g. cubic boron nitride) as well as metals and fibre reinforced composites using both percussive and trepanning techniques. The use of SHG Nd:YAG-laser for deep hole drilling may therefore be a possible alternative to Cu vapour lasers. A comparison of hole drilling at the fundamental and second harmonic wavelengths is presented.