L14_A
Transitions
Stimulated emission
Stimulated emission <-> Gain
Gain needs pump
Calculating the gain: Einstein A,B coefficients
L14_B
Amplification: gain
Population inversion
Inversion: pumping the gain medium
Different gain media
Rate equations for a two-level system
Two-level system does not give gain
L14_C
Rate equations for a three-level system
Three-level system: gain possible
Rate equations for a four-level system
Four-level system: gain easy
Two-, three-, and four-level systems
L14_D
LASER
What does cavity do?
L14_E
Cavity gives longitudinal modes
Single-mode laser operation
Types of Lasers
Laser spectrum
The Helium-Neon Laser
Ion Lasers
Dye lasers
Titanium:Sapphire (Ti:S)
Diode Lasers
Two major type of LD
Some everyday applications of diode lasers
Fiber lasers
LASIK
Laser micro-machining
