Modification lines by local melting inside glass were written by focusing picosecond laser pulses at high repetition rate with temporal modulation of pulse energies. It was found that straight modification lines with homogeneous stress distribution was able to be written by ps laser irradiation with temporal energy modulation, while modification lines written by ps laser irradiation without modulation had curved boundaries and concentrated stress. The threshold of the crack generation was

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... with temporal energy modulation (22 µJ of the average pulse energy) than that without modulation (16.5 µJ of the average pulse energy), which resulted in about 1.3 times larger width of modification line with modulation than that without modulation. In addition, the elongation of a modification line in the laser propagation direction could be suppressed with modulation. The mechanism of the suppression of stress and crack generation with temporal energy modulation will be discussed according to the movement of light absorbed region during laser irradiation.