2.8 lasers Flashcards
what is stimulated emission
When an incoming photon causes an excited electron to fall to a lower energy level, releasing a second photon that is coherent with the first
What is population inversion?
Population inversion is a process required by laser technology, when there are more electrons in the upper level than the lower level. More electrons need to be in the upper level compared to the lower level because otherwise, the process of absorption will have a higher chance of taking place as opposed to stimulated emission.
what are semiconductor lasers
lasers that are smaller and cheaper to produce. Therefore, they are often used in domestic appliances such as CD and DVD players. Barcode scanners and laser printers will also use semiconductor lasers. In addition to this, semiconductor lasers use much less power (and are more efficient) than other lasers allowing them to be run on low voltage sources - suitable for domestic appliances.
What does LASER stand fo
Light Amplification by Stimulated Emission of Radiation.
What is spontaneous emission?
When an excited electron falls to a lower energy level without external influence, emitting a photon at random direction and phase
How does stimulated emission differ from spontaneous emission?
Stimulated emission produces photons that are in phase, have the same frequency, and travel in the same direction as the incident photon.
What is optical pumping?
The process of supplying energy (e.g. via light or electrical discharge) to excite electrons and achieve population inversion
What role do mirrors play in a laser cavity?
They reflect photons back and forth to increase the chance of stimulated emission; one mirror is partially transparent to allow the beam to exit.
Why don’t 2-level lasers work effectively
Because as soon as an electron drops to the ground state, it increases absorption, making it difficult to achieve population inversion.
What is a 3-level laser system?
A system where electrons are pumped from the ground state to a high-energy state, quickly drop to a meta-stable state, and then emit laser light as they transition to a lower state.
