What are the states of light involved in stimulated emission?

Stimulated emission is a fundamental process in laser operation where an incoming photon induces an excited electron in an atom or molecule to drop down to a lower energy state, emitting a second photon that is coherent with the first.

The correct answer encompasses all the mentioned states, as each plays a role in the context of stimulated emission:

• In the excited state, electrons have absorbed energy and are temporarily elevated to a higher energy level. This state is crucial for stimulated emission because it is these high-energy electrons that will drop down to lower energy states upon interaction with incoming photons, resulting in the emission of coherent light.

• The ground state represents the lowest energy level of an atom or molecule. Although electrons initially reside here, they must be energized to reach the excited state to participate in stimulated emission. Understanding the ground state is vital as it serves as the reference point for energy transitions.

• Metastable states occur when excited electrons remain in an excited configuration longer than typical excited states. These states are vital for laser action because they increase the likelihood of stimulated emission; electrons in metastable states can accumulate and lead to a population inversion necessary for laser operation.

Each of these states is interrelated in the process of stimulated emission, making the comprehensive answer that includes all of