IPL Ultra is in the SHR, or Super Hair Removal, cosmetic systems class. Such medical devices operate via building up heat into the hair follicle while keeping a stable and high output frequency but with a low energy density. Outputting the energy like that, and building up the heat levels slowly, allows for the hair removal procedure to be virtually pain free and without extra risks of burning.
The IPL abbreviation means Intense Pulsed Light, and systems marked as using this tech work via pulsing light shots very rapidly. If the pulse has a square wavelength, then superior levels of uniformity of the energy output can be maintained. The peak energy levels are reached almost instantly and then kept for the entire time the pulse is active, with zero fluctuation of the wave.