The first step to getting output from a laser is to excite an active medium. What is this process called?

The correct answer is A. Pumping.

Pumping is the process of transferring energy to an active medium in a laser. This energy can be in the form of light, heat, or electricity. The energy is used to excite the atoms or molecules in the active medium, which causes them to emit light.

The other options are incorrect.

• Exciting is not a technical term in laser physics.
• Priming is the process of preparing an active medium for laser action. This is done by removing impurities from the medium and by ensuring that the medium is at the correct temperature and pressure.
• Raising is not a technical term in laser physics.