Lasers operate based on the principles of quantum theory, specifically through the behavior of electrons within atoms. When energy is applied, electrons can transition between different energy levels, a process known as excitation. This transition is a key aspect of quantum mechanics. As electrons return to their lower energy states, they emit photons, which are the fundamental particles of light. This emission process is what generates the coherent light characteristic of lasers. Understanding these quantum interactions is essential for grasping how lasers function.