Sample interview questions: Describe the process of stimulated emission and its importance in laser physics.
Sample answer:
Stimulated emission is a fundamental process in laser physics that enables the amplification of light and the generation of coherent, monochromatic beams. Here’s a detailed description of stimulated emission and its importance:
Process of Stimulated Emission:
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Excited State: In a laser medium (e.g., a gain medium), atoms or molecules are first excited to a higher energy level, known as the excited state. This can be achieved through various methods such as optical pumping, collisional excitation, or electrical discharge.
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Stimulated Photon: When a photon of specific energy interacts with an excited atom or molecule, it can trigger the release of a second photon with the same energy, phase, and direction. This process is called stimulated emission.
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Population Inversion: For stimulated emission to dominate over spontaneous emission (random emission of photons), a population inversion must be established. This means that there are more atoms or molecules in the excited state than in the ground state. This condition is achieved through various techniques like pumping and energy transfer mechanisms.
Importance in Laser Physics:
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Light Amplification: Stimulated emission allows for the amplification of light. As photons undergo stimulated emission, they interact with other excited atoms or molecules, causing a cascade of photon releases. This results in the exponential amplification of light intensity, leading to the production of an intense, highly directional beam.<... Read full answer