Lecture 5 :
Recombination Rate:
Radiative Recombination:
Recombination on Defects or Traps:
Auger Recombination:
Total Recombination: Trap + Radiative + Auger
Total Carrier Lifetime formula: HW2 Prob 4
Band Diagrams:
1) Normal PN junction:
2) Heterostructure P-I-N junction:
Important: Draw heartbeat when there’s a discontinuity.
Lecture 6:
Semiconductor Quantum Well:
Energy of Quantization:
There’s a lot related to Quantum Wells, refer slides if more info is needed.
Energy conservation/ Momentum Conservation:
Population Inversion occurs -> amplification occurs -> laser works
Condition for population inversion: Fe + Fh > 1
Laser Wall Plug Efficiency:
Non Radiative Recombination:
Stimulated Recombination:
Photon Balance Equation/ Photon Loss/ Optical Loss - Alpha I (αi ):
Optical Loss at Mirrors ( Alpha M ) (αm ):
Rate Equations for carriers below threshold:
Radiative efficieny:
Extraction efficiency:
Rate Equations of Carriers Above Threshold:
Total gain given here, read last line:
Optical energy in the cavity: Energy loss through the mirror:
Optical Power Output through the mirrors:
Lecture 7:
Gain spectrum and temperature performance of a diode semiconductor laser.
MATERIAL GAIN :
Ef :
Optical Gain Spectrum:
Modal Gain:
Threshold condition and Modal gain after Threshold:
Threshold Current and Carrier Rate Equation:
Light Current characteristics and Rate Equations:
Stored optical energy in the cavity:
Energy loss rate through the mirrors:
Output power from the mirrors:
Threshold Gain:
Threshold current:
After threshold carrier rate equation:
After threshold steady state:
Optical confinement:
Output Power:
TEMPERATURE DEPENDENCE OF GAIN AND THRESHOLD CURRENT:
Candidate mechanisms for temperature performance degradation:
The higher threshold current leads to higher active area temperature(positive feedback)
Active area heating/ Thermal resistance
Effect of temperature on the laser performance: