Lecture 8: Laser amplifiers

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Gain coefficients The gain coefficient is a decreasing function of the photonflux density . When equals its saturation value s () = s , the gain coefficient is reduced to half its unsaturated value. ) 1 0.5 0 0.01 0.1 1 10 s () 106 106
Amplified spontaneous emission The resonant medium that provides amplification via stimulated emission also generates spontaneous emission. The light arising from the spontaneous emission, which is independent of the input to the amplifier, represents a fundamental source of laser amplifier noise. Whereas the amplified signal has a specific frequency, direction, and polarization, the noise associated with amplified spontaneous emission (ASE) is broadband, multidirectional, and unpolarized. => it is possible to filter out some of this noise by following the amplifier with a narrowband optical filter, a collection aperture, and a polarizer. 107
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Lecture 8: Laser amplifiers Opt
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Optical transitions 3
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Photon-matter interaction processes
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Three basic photon-matter interacti
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Probability per second of a spontan
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Spectral lineshape The spectra
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Homogeneous broadening If all o
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Inhomogeneous broadening Howeve
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Transition rates The transiti
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Transition rates For the upward tr
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Transition rates The total induce
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Blackbody radiation A system und
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Planck’s law of blackbody radiati
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Transition rates In thermal equili
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Boltzmann distribution Energy E E 2
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Transition rates Therefore, the s
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Transition cross section For the
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Optical absorption and amplificatio
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Optical absorption and amplificatio
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Resonant optical susceptibility Fo
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Resonant optical susceptibility Th
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Population inversion 43
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Population inversion A nonequilibr
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Rate equations The net rate of chan
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Population inversion Population in
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Two-level systems No matter how a
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Two-level systems Take the upward
Page 55 and 56: Two-level systems Intuitively, th
Page 57 and 58: Quasi-two-level systems By pumpi
Page 59 and 60: Population inversion in three-level
Page 61 and 62: Three-level systems The parameter
Page 63 and 64: Four-level systems pump h p Nonradi
Page 65 and 66: Neodymium-doped glass Nd 3+ :glass
Page 67 and 68: Coherent optical amplifiers Gain, n
Page 69 and 70: Coherent light amplification As
Page 71 and 72: Population inversion Light tran
Page 73 and 74: Real coherent amplifiers Real
Page 75 and 76: Gain and bandwidth The wave is am
Page 77 and 78: Gain coefficient As the incident
Page 79 and 80: Gain coefficient The coefficient
Page 81 and 82: Gain bandwidth The dependence
Page 83 and 84: Phase‐shift coefficient The las
Page 85 and 86: Rate equations 2 R 2 1/ 21 = 1/ sp
Page 87 and 88: Rate equations in the absence of am
Page 89 and 90: Rate equations in the presence of a
Page 91 and 92: Four-level pumping Pump R Laser W i
Page 93 and 94: Four-level pumping In most four-le
Page 95 and 96: Four-level pumping Under these c
Page 97 and 98: Three-level pumping Rapid decay S
Page 99 and 100: Three-level pumping The population
Page 101 and 102: Three-level pumping The dependence
Page 103 and 104: Saturated gain in homogeneously bro
Page 105: Gain coefficients This represents t
Page 109: Amplifier noise The ASE of a la
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Lecture 8: Laser amplifiers

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