Laser Power Density: Laser power density refers to the amount of laser power per unit area and is usually measured in watts per square meter (W/m²). It gives an indication of how concentrated the laser energy is on a given surface. High power density can lead to increased heating and potential material damage.

Energy Density: Energy density is a measure of the amount of energy stored in a given volume or mass. In the context of lasers, it might refer to the energy delivered by the laser per unit area, often measured in joules per square centimeter (J/cm²). This is relevant in applications such as laser material processing and medical treatments.