Which of the following can be an Active Medium in a laser?

Which of the following can be an Active Medium in a laser?

• A. The Electrical Circuit
• B. The Outer Casing
• C. Solid state, a gas, dye, or a semiconductor
• D. The Cooling System

Answer: (C)

In a laser, the active medium is the material where light is amplified by stimulated emission, so it must be something that can be pumped to create population inversion and provide optical gain. The best answer describes the active medium as solid state, a gas, a dye, or a semiconductor, which covers the main families of laser gain media: solid‑state crystals (like Nd:YAG), gas lasers (such as CO2 or HeNe), dye lasers (organic dye solutions), and semiconductor lasers (diode lasers). The other components—an electrical circuit, the outer casing, or a cooling system—support the laser’s operation but do not themselves act as the light-amplifying medium.

In a laser, the active medium is the material where light is amplified by stimulated emission, so it must be something that can be pumped to create population inversion and provide optical gain. The best answer describes the active medium as solid state, a gas, a dye, or a semiconductor, which covers the main families of laser gain media: solid‑state crystals (like Nd:YAG), gas lasers (such as CO2 or HeNe), dye lasers (organic dye solutions), and semiconductor lasers (diode lasers). The other components—an electrical circuit, the outer casing, or a cooling system—support the laser’s operation but do not themselves act as the light-amplifying medium.