Efficacy in laser treatment has always necessitated a balance between the increased therapeutic effect associated with the use of higher-energy fluences and the associated increased risk of adverse events, particularly the risk of scarring. The development of fractional photothermolysis technologies has greatly shifted this balance, allowing for efficacy with decreased risks of adverse events.

Rather than treating the entire skin surface in a uniform pattern, fractional photothermolysis utilizes very small microbeams of diameter 100–200 μm to create microscopic thermal wounds, while sparing tissue surrounding these wounds. The microthermal zones are subjected to high-energy fluences, which result in homogenization of the dermis as well as damage to the overlying epidermis, with the formation and extrusion of necrotic epidermal debris. The intervening areas between the microthermal zones are not subjected to this high fluence but are gently heated by the diffusion of energy. This technology allows for the use of high-energy fluences with potentially greater clinical efficacy. As only a portion of the surface is subjected to the high-energy fluences, there is less downtime associated with the treatment as well as a potentially decreased risk of adverse events.

The Affirm laser (Cynosure Inc.) is a new microrejuvenation technology that incorporates the concepts of fractional photothermolysis and Cynosure's new Combined Apex Pulse array (CAP). The Affirm laser is a 1,440-nm Nd:YAG laser coupled with a special lens that incorporates approximately one thousand diffractive elements, called the CAP array. Originally, the Affirm device was developed with a single 1,440-nm-wavelength laser output device.