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Interaction of radiation with atoms and ions (I)

Interaction of radiation with atoms and ions (I). Absorption- Stimulated emission. E 2. W 12 =W 21. E 1. More definitions. Cross section. Absorption coefficient. Gain. Spontaneous emission. Interaction of radiation with atoms and ions (II). Line broadening. Homogeneous (Lorentz)

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Interaction of radiation with atoms and ions (I)

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  1. Interaction of radiation with atoms and ions (I) Absorption- Stimulated emission E2 W12 =W21 E1 More definitions Cross section Absorption coefficient Gain Spontaneous emission

  2. Interaction of radiation with atoms and ions (II) Line broadening Homogeneous (Lorentz) Collisions Spont. emission Inhomogeneous (Gauss) Doppler Local field Phonons Saturation 2 2 1 1 High absorption Reduced absorption

  3. Ray and wave propagation through optical media Matrix- formulation of Geometric Optics Material with index n lens Gaussian Beam ABCD law

  4. Stable resonators Stability condition General case Two-mirror resonator Round trip matrix Gaussian beam solution Single passage matrix Frequencies Spectral width

  5. Continuous Wave Laser Behavior Rate equations cw-laser Threshold Stationary solution

  6. Transient Laser Behavior Q-switching: High losses High population inversion Switching of losses Pulse (ns) Mode-locking Frequency domain: Modes “in phase” Time domain: Pulse train, periodicity: Gaussian Phase velocity Group velocity Group delay Group delay dispersion

  7. Properties of Laser beams Spatial coherence Temporal coherence Measurement: Michelson interferometer Measurement: Young’s double slit interferometer Temporal coherence: monochromaticity Spatial coherence: directionality Laser: good temporal coherence if monomode Laser: good spatial coherence if one transverse mode Thermal light: Brightness: Laser and thermal light have different statistical properties different high-order coherence For a Gaussian beam (high brightness)

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