A picosecond laser delivers energy in pulses lasting trillionths of a second. Because the pulse is shorter than the time it takes heat to spread into surrounding tissue, the pigment particle is intended to absorb the energy and shatter mechanically rather than relying primarily on heat.
The fragments are then cleared by the body over the following weeks. Compared with older nanosecond, Q-switched devices, the shorter pulse means less heat deposited into the skin around the target, which matters a great deal on pigmented skin.
That is a real advantage. It is not immunity. Shorter pulses reduce thermal injury; they do not abolish it. Every published series on picosecond lasers in Asian skin still records adverse events, and the literature is consistent that Asian skin carries a higher incidence of laser complications including burns, hyperpigmentation, hypopigmentation and textural change, which is why gentler settings are recommended rather than more powerful ones.