Source: ResearchGate

Laser Transitions

Understanding Laser Transitions

A laser transition, also known as an amplifier transition, occurs between two electronic levels of a laser-active ion. This transition allows for stimulated emission, leading to optical amplification that is utilized in lasers and optical amplifiers.

Characteristics of Efficient Laser Transitions

In order for an optical transition to serve as an efficient laser transition, certain conditions need to be met:

• The upper level must be effectively populated, often achieved through optical pumping.
• Stimulated emission from the upper level to the lower level should dominate over other transitions, with a longer upper-state lifetime compared to the stimulated emission rate.
• There should be a mechanism to depopulate the lower laser level quickly after stimulated emission to prevent strong reabsorption effects.

Examples of Laser Gain Media

Some laser gain media, like neodymium ions in Nd:YAG, exhibit nearly ideal laser transitions. For instance, Nd:YAG demonstrates a transition from the upper Stark manifold 4F 3/2 to the lower manifold 4I 11/2, enabling stimulated emission at 1064 nm. Efficient pumping is achieved around 808 nm, and rapid depopulation of the lower level occurs via multi-phonon transitions.

On the other hand, there are media with quasi-three-level laser transitions, such as the 1030-nm and 1050-nm transitions in Yb:YAG. These transitions may have reabsorption effects due to the lower level belonging to the ground state manifold, leading to increased threshold pump power requirements.

Exploring Laser Transitions Further

Understanding laser transitions is crucial for optimizing laser designs and achieving efficient laser operation. By studying the characteristics of different laser gain media, researchers can develop advanced laser systems with improved performance.

Source: Fosco Connect
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