Lecture 8: Laser amplifiers

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Optical transitions Optical absorption and emission occur through the interaction of optical radiation with electrons in a material system that defines the energy levels of the electrons. Depending on the properties of a given material, electrons that interact with optical radiation can be either those bound to individual atoms or those residing in the energyband structures of a material such as a semiconductor. The absorption or emission of a photon by an electron is associated with a resonant transition of the electron between a lower energy level |1> of energy E 1 and an upper energy level |2> of energy E 2 . 4
Photon-matter interaction processes There are three fundamental processes electrons make transitions between two energy levels upon a photon of energy. E = h 12 = E 2 – E 1 • A two-level system is a model system that only contains two energy levels with which the photon interacts. 5
Page 1 and 2: Lecture 8: Laser amplifiers Opt
Page 3: Optical transitions 3
Page 7 and 8: Three basic photon-matter interacti
Page 9 and 10: Probability per second of a spontan
Page 11 and 12: Spectral lineshape The spectra
Page 13 and 14: Homogeneous broadening If all o
Page 15 and 16: Inhomogeneous broadening Howeve
Page 17 and 18: Transition rates The transiti
Page 19 and 20: Transition rates For the upward tr
Page 21 and 22: Transition rates The total induce
Page 23 and 24: Blackbody radiation A system und
Page 25 and 26: Planck’s law of blackbody radiati
Page 27 and 28: Transition rates In thermal equili
Page 29 and 30: Boltzmann distribution Energy E E 2
Page 31 and 32: Transition rates Therefore, the s
Page 33 and 34: Transition cross section For the
Page 35 and 36: Optical absorption and amplificatio
Page 37 and 38: Optical absorption and amplificatio
Page 39 and 40: Resonant optical susceptibility Fo
Page 41 and 42: Resonant optical susceptibility Th
Page 43 and 44: Population inversion 43
Page 45 and 46: Population inversion A nonequilibr
Page 47 and 48: Rate equations The net rate of chan
Page 49 and 50: Population inversion Population in
Page 51 and 52: Two-level systems No matter how a
Page 53 and 54: Two-level systems Take the upward
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Two-level systems Intuitively, th
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Quasi-two-level systems By pumpi
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Population inversion in three-level
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Three-level systems The parameter
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Four-level systems pump h p Nonradi
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Neodymium-doped glass Nd 3+ :glass
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Coherent optical amplifiers Gain, n
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Coherent light amplification As
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Population inversion Light tran
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Real coherent amplifiers Real
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Gain and bandwidth The wave is am
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Gain coefficient As the incident
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Gain coefficient The coefficient
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Gain bandwidth The dependence
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Phase‐shift coefficient The las
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Rate equations 2 R 2 1/ 21 = 1/ sp
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Rate equations in the absence of am
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Rate equations in the presence of a
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Four-level pumping Pump R Laser W i
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Four-level pumping In most four-le
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Four-level pumping Under these c
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Three-level pumping Rapid decay S
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Three-level pumping The population
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Three-level pumping The dependence
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Saturated gain in homogeneously bro
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Gain coefficients This represents t
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Amplified spontaneous emission T
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Amplifier noise The ASE of a la
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Lecture 8: Laser amplifiers

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