What is the source of energy (power supply) that creates excitation of the laser medium?

• A. Power Pumping Station
• B. Optical Cavity
• C. Active Medium
• D. Flashing Lights/Audible Signals

Answer: (A)

Pumping energy is required to create population inversion in the laser medium. The external energy source that does this is the pumping station, which supplies the excitation—electrical power or optical energy from lamps, diodes, or other means—to lift electrons into higher energy levels. Once enough atoms are excited, stimulated emission takes over and the light is amplified as it reflects within the optical cavity. The active medium is the material that provides gain, but it is the pump that supplies the necessary energy; the cavity simply provides feedback. Flashing lights or audible signals can be a way to deliver pulsed pumping in some systems, but the essential source of excitation energy remains the pumping station.