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lecture34 - 34 Lasers II Four-level systems are the best...

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34. Lasers II Four-level systems are the best for lasers Steady-state conditions: threshold longitudinal modes Some laser examples
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Two-, three-, and four-level systems Two-level system Laser Transition Pump Transition At best, you get equal populations. No lasing. Four level systems are the best for making a laser. Four-level system Lasing is easy! Laser Transition Pump Transition Fast decay Fast decay Three-level system If you hit it hard, you get lasing. Laser Transition Pump Transition Fast decay
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