Physics-II(Optics & Waves)

Lasers operate based on interactions of matter and light, primarily through the mechanisms of absorption, spontaneous emission, and stimulated emission, with stimulated emission being fundamental for laser operation. A critical condition for lasing is population inversion, where more atoms are in an excited state than in the ground state, allowing for amplified light through stimulated emission. Different types of lasers include gas, solid-state, and dye lasers, each having unique properties and applications. Laser beams share distinctive qualities such as monochromaticity, coherence, directionality, and exceptional brightness, leading to a myriad of uses in science, engineering, and medicine.