Steady-State Laser Pumping and Population Inversion

Table of Contents:

  1. Four-Level Laser System
  2. Four-Level Pumping Analysis
  3. Fluorescent Quantum Efficiency
  4. Four-Level Population Inversion
  5. Three-Level Laser System

FOUR-LEVEL LASER SYSTEM

In a previous section, we discussed the basics of multi-level systems. Here, we will go more in depth with what is meant by a four-level system. As you might imagine, a four-level system is that you have 4 quantum levels that comprise the scheme of your laser. A gain medium may have other quantum levels (analogous to orbital levels if you are more familiar with chemistry), but a four level laser system means that the absorption, initial decay, and spontaneous and/or stimulated emission all occur within four levels. The diagram below shows how the laser scheme may look like.

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