Abstract
We applied the femtosecond laser-assisted etching technique, that is, irradiation of focused femtosecond
laser pulses followed by selective chemical etching, to volume removal inside sapphire.
At room temperature, volume etching only slightly advanced while residue remained inside the
volume. By increasing the etching temperature, complete volume etching without residue was
achieved. Complete etching was, however, accompanied by undesirable phenomena of surface pits
or cracks, which are expected to be excluded through further improvement of processing.