Source: ResearchGate

<>

Lasing Without Inversion

Understanding the Concept

Traditionally, lasers operate on the principle of population inversion, where the upper laser level has a higher population than the lower level, enabling stimulated emission and positive net gain. However, in the 1990s, researchers discovered that lasing without inversion is feasible by inducing quantum coherence in the gain medium through an additional optical or microwave field.

This approach involves creating two pathways for atoms to transition from the ground state to the excited state, one direct and the other via a third energy level. By inducing quantum coherence, the probability amplitudes for both pathways cancel out, suppressing reabsorption and allowing for a positive net gain even with a small population in the upper state.

Potential Applications

Lasing without inversion could be beneficial for developing lasers that operate at very short wavelengths, where achieving population inversion is challenging. While this quantum-mechanical effect is intriguing, its practical advantages are still uncertain. As of now, lasing without inversion remains more of a theoretical concept than a widely used technique.

Future Research

Further studies are needed to explore the practical implications and potential applications of lasing without inversion. Researchers continue to investigate this phenomenon to determine if it can be harnessed for practical laser technologies in the future.

Source: IOPscience – Institute of Physics
Feel free to comment your thoughts.