Picosecond Lasers

The first decision is pulse duration. Picosecond pulses fracture pigment mechanically, with less of the thermal component a nanosecond Q-switched pulse carries; both are in active clinical use and both remain on sale, so this is a question of what you treat and what you want to charge rather than of one being obsolete. Nanosecond Q-switched platforms cost appreciably less and remain the standard workhorse for dark ink. Picosecond platforms cost more and are the ones marketed on shorter courses and stubborn multi-colour work.

Wavelength coverage decides which inks you can accept. 1064nm handles black and dark blue and travels deepest; frequency-doubled 532nm addresses red and orange and superficial pigment. Greens, sky blues and purples are the inks that defeat a two-wavelength machine, which is what the 585nm and 650nm dye handpieces exist for. If you intend to advertise multi-colour removal, buy the handpieces up front — retrofitting is rarely cheaper.

Beyond that, look at the beam profile and the arm. A top-hat profile spreads energy flat across the spot instead of peaking in the middle, which is what lets fluence be raised without a hot core in every pulse. A seven-joint articulated arm holds alignment far better than a fibre over a machine's life. Neither appears in the headline specification, and both are what a treatment looks like in year three.