How is fluence expressed in terms of units?

Fluence, which is a measure of the energy per unit area delivered by a laser, is correctly expressed in Joules per square centimeter. This unit reflects the total energy (in Joules) that is concentrated over a specific area (in square centimeters), allowing for a clear understanding of the energy density a treatment may deliver to a targeted area during laser procedures.

Using Joules per square meter or Joules per cubic meter would not accurately represent fluence, as these units either denote energy spread over an area that is too large (square meter) or energy distributed in a volume (cubic meter), both of which do not capture the specific energy application that occurs during laser treatments. Additionally, Joules per liter is a measurement typically reserved for concentrations of substances in a solution and does not apply to the concept of fluence in laser therapy.

Hence, the answer that reflects the appropriate and commonly accepted unit for fluence in the context of laser treatments is Joules over centimeter squared.