a dermatological treatment method includes directing laser energy having a wavelength of 2 . 79 μm onto skin . according to disclosed methods , the energy can function to ablate a first portion of epidermal tissue , coagulate an underlying second portion of epidermal tissue , and promote collagen formation in tissue of the underlying dermis . tn an exemplary treatment apparatus , a laser using a ysgg gain medium is mounted in a handpiece . the handpiece may include a two - axis scanner to allow for uniform scanning of the energy over the tissue surface .