2.8 Lasers Flashcards
What does LASER stand for?
Light Amplification by Stimulated Emission of Radiation
Photon absorption
The absorbing of a photon, raising an electron to a high energy level
Photon emission
The emitting of a photon, allowing an electron to fall to a lower energy level
Spontaneous emission
Is the spontaneous emission of a photon by an electron on a higher (unstable) energy level, making it fall to a lower energy level
Stimulated emission
Is the emission of a photon from an excited atom, triggered by a passing photon of energy equal to the energy gap between the excited state and a state of lower energy
Population inversion
Is where a higher energy state is more populated with electrons than a lower energy state of the same system
Pumping
Feeding energy into the amplifying medium of a laser to produce a population inversion
Laser light is …
Monochromatic
coherent
parallel beam
polarised
Non laser light is …
Non-monochromatic
different wave lengths
different directions
non coherent
non polarised
Explain the 3 energy level laser system
- Electrons are promoted from ground state to E3
- Electrons drop quickly to the metastable E2
- E2 > E1 for the photons to be emitted in enough quantities to produce light
Explain the 4 energy level laser system
- Electrons are promoted from ground state to E3
- Electrons drop quickly to the metastable E3
- E3 > E2 for the photons to be emitted in enough quantities to produce light
- Another fast drop from E2 to E1, this make E2 empty so population inversion works better
Semiconductor lasers benefits
Cheaper
Smaller
More efficient
Easy to mass produce
Uses for semiconductor lasers
Inside DVD and CD players
Barcode readers
Telecommunications
Image scanning
Laser surgery
