Lasers used to be strictly sci-fi and superhero territory, but they are increasingly becoming ubiquitous in science. Laser started out as an acronym: Light Amplification by Stimulated Emission of Radiation. Despite the impressive title, the physics of lasers are relatively straightforward. Lasers can only be produced artificially, because they require an extremely narrow beam of light in which all the light waves have the same wavelength. As these waves all align with each other, the resulting beam of light is very narrow, very bright, and focuses a large amount of energy on a small area. Let’s read on to learn more about this bright idea!
By analyzing questions, you can see patterns emerge, patterns that will help you answer questions. Qwiz5 is all about those patterns. In each installment of Qwiz5, we take an answer line and look at its five most common clues. Here we explore five clues that will help you answer a tossup on lasers.
Population inversion refers to a redistribution of energy within an atom so that a laser can be created. In a system at equilibrium, more atoms tend to be in a lower energy, or ground state. Population inversion is induced when energy is introduced into the system. This raises more atoms to an excited state, inverting the usual distribution of atoms by energy level.
If a system is in a state of population inversion, stimulated emission can occur. In stimulated emission, excited atoms are stimulated by the same level of energy they would emit naturally. The incoming energy into the system is in phase with the energy the atoms emit as they return to the ground state. With incoming and outgoing energies in phase a coherent stream of photons, AKA a laser, is created.
Q-switching refers to a particular form of laser propagation. Typically, lasers are emitted as a continuous stream of photons. In Q-switching, the laser is pulsed. The repetition of these pulses can be rapidly increased in a technique known as mode locking.
The first laser was created in 1960 by American engineer Theodore Maiman. Maiman formed a ruby crystal into a cylinder and bombarded the cylinder with flashes of white light to create stimulated emission. Ruby crystals are still used as a gain medium to create lasers to this day.
Stimulated emission is necessary to create a laser, but it is not sufficient. Pumping external energy into a medium at first results in simply spontaneous emission. In order for stimulated emission to predominate over spontaneous emission, the beam must be amplified. This amplification is achieved by the optical cavity, several mirrors that bounce the beam of light back and forth through the medium to change it from spontaneous to stimulated emission.
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