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LASER (Light Amplification by Stimulated Emission of Radiation) - Coggle…
LASER
(Light Amplification by Stimulated Emission of Radiation)
Characteristics
Directional
Emerges in very thin beam with very little diverge
Monochromatic
It contains essentially only one specific wavelength
Coherent
Different parts of laser beam are related to each other in phase - total constructive interference
Formula
Energy
E = hc / λ
E = Energy (J OR eV)
h = Planck's constant = 6.63 x 10^(-34) J.s = 4.14 x 10^(-15) eV.s
λ = Wavelength (m)
1 eV = 1.602 x 10^(-19) J
Thermodynamic Equilibrium
N1/N2 = exp^(- E / kT)
N1/N2 - Predict the distribution of atoms at any given energy level under thermal equilibrium
N1 = Number of atoms at lower energy level
N2 = Number of atoms at higher energy level
E = Energy difference between higher energy level & lower energy level (J OR eV)
k = Boltzmann constant (k) = 1.38 x 10^(-23) J/K = 8.6 x 10^(-5) eV/K
T = Temperature (in Kelvin)
It cannot be used for inversion population
Stimulated emission
Metastable state and population inversion are preconditions for stimulated emission
metastable state
mean lifetime of atoms at it = around 10^(-3) secs to 10^(-5) secs
atoms at metastable state have a longer lifetime than normal energy state/level
population inversion
when the population of atoms accumulated at the upper energy level is higher than the population at a lower energy level
leads to light amplification
difference between Stimulated Emission and Spontaneous Emission
spontaneous emission can have multiple wavelength
stimulated emission made of one single wavelength
spontaneous emission do not require external energy
stimulated emission triggered by external energy to kick start the process
additional atom released with the same energy
How it happens
2) Quantum energy of the incident photon = difference in between the two energy levels. (Main Requirement)
3) The incident photon would then stimulate and transit the atoms from the higher energy level to a lower energy level.
1) The atoms that are excited will encounter an incident photon
4) A second photon with a similar amount of energy is then produced.
Applications
lasik
Laser printing
removal of tattoos
Laser pointer