The dynamics of the ablation process was investigated in bone using two pulses separated by a variable time delay. In one experiment two sub- threshold 7.5 nsec duration pulses at $lambda $EQ 355 nm with pulse separation ranging between 1 ns and 100 msec were used to ablate bone. Crater depths remained approximately constant for pulse separations up to $APEQ 100 nsec, then decreased monotonically in time to zero at 10 msec pulse separation. In another experiment the second pulse was replaced by a 7.5 nsec duration pulse at $lambda $EQ 532 nm. The combination of sub-threshold pulses at two different wavelengths also ablated bone with a cutting quality matching that of the more strongly absorbed $lambda $EQ 355 nm wavelength. Crater depths from dual wavelength ablation increased with increasing fluence in either contributing pulse. Practical consequences of these experiments are discussed.
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