The Er:YAG laser emits a monochromatic wavelength of infrared light at 2,940 nm, which closely approximates the major peak absorption of water near 3,000 nm. In the water-rich epidermis, laser energy is immediately absorbed, yielding precise tissue ablation with minimal thermal diffusion.

Erbium lasers may be categorized based on their pulse durations, or the time during which cutaneous tissue is exposed to laser energy. Thermal diffusion and collateral spread of laser energy are directly proportional to longer pulse durations.

The short-pulsed erbium laser was initially approved by the Food and Drug Administration in 1996 for skin resurfacing as an alternative to the carbon dioxide laser, with the benefits of a shorter recovery period and fewer side effects. With pulse intervals in the microsecond range, effective tissue ablation with minimal collateral damage is safely achieved. Quality-switched (or Q-switched) erbium lasers were also developed with ultrashort pulse durations in the nanosecond range. As a downside, little to no thermal coagulation or tissue contraction occurs with either the short or ultrashort pulse durations due to minimal spread of thermal energy. However, variable-pulsed erbium lasers were recently developed with longer pulse durations, in the millisecond range, with thermal diffusion of laser energy falling somewhere between the traditional erbium and CO2 lasers. Longer pulse durations permit a wider spread of thermal energy, resulting in thermal coagulation of collagen and tissue contraction – an advantage when resurfacing beyond the epidermis.