Two, Three, and Four Level Schemes

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Two, Three, and Four Level Schemes
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Saturation of a two-level system
Steady state
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Maximum gain of 2-level scheme
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Three-level scheme Ruby
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Ruby laser
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Three level laser
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Population Inversion
Inversion condition ?2gt?3
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Simplified case
?2gtgt?3
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Example for Ruby
What is the power actually absorbed by the atoms
at transparency?
Total number of atoms in state 2 NV/2
?21
If we drive the laser to two-times transparency
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Gain coefficient
If we drive the laser at Ppump2Ptran
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Cr 1s22s22p63s23p63d54s1
Ti 1s22s22p63s23p63d24s2
Nd 1s22s22p63s23p63d104s24p64d104f45s25p66d2
Er 1s22s22p63s23p63d104s24p64d104f125s25p66d2
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Rare Earth Doped Lasers
NdYAG, NdGlass, NdYVO4 1060nm
ErYAG, ErGlass,1550nm, 2840nm
YbGlass 1040nm
HoYAG, HoYLF 2100nm
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Four Level Lasers Nd Y3Al5O12
NdYAG Energy Levels
NdYAG -absorption
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Flashlamps Xe and Kr
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Pumping Geometries
NdYAG laser
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Diode pumped NdYAG
diode
Collimating diode
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End pumped laser
Side pumped laser
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Balance Equations
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Steady State Solution
No transparency power
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Numbers for NdYAG
Expected Gain
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High Power Diode Pumped NDYAG Lasers