Question: What is the process responsible for producing photons in a diode laser?
Correct Answer As electrons in semiconductor materials are excited to higher energy levels they leave behind “holes” in the lower energy bands. As the electron relaxes back to its normal energy, the electrons fill the holes, recombine, and a photon may be produced.
Correct Answer The first laser was a solid state laser. Solid state refers to any solid material like a glass rod. Diode lasers are very common because they are used to read compact disks and digital video disks in computers, CD players, and DVD players. Before diode lasers, the most common type of laser may have been the helium-neon laser, in which the active medium is a combination of the two gasses helium and neon.
Question: After the first photons of light are produced, which process is responsible for amplification of the light?
Correct Answer The word “laser” is actually an acronym for light amplification by stimulated electron radiation. Atoms or molecules of the active medium that have been excited to a higher energy level are stimulated by a passing photon to relax to a lower energy level and emit a photon that is indistinguishable from the passing photon, thereby increasing the number of photons like the incident one.
Question: Once the active medium is excited, the first photons of light are produced by which physical process?
Correct Answer Spontaneous emission is what you see with most “glow in the dark” toys. You excite the toy by exposing it to bright light, then the toy glows in the dark by spontaneously emitting photons as the excited atoms relax back down to their normal state.
Question: The first step to getting output from a laser is to excite an active medium. What is this process called?
Correct Answer A collection of atoms or molecules that can be excited to a higher energy state is called an active medium. Before lasing can occur, the active media is “pumped”. The process of raising the atoms in the active media from a lower energy state to a higher state is like pumping water up from a well.