Lecture 8: Laser amplifiers

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Erbium-doped silica fibers Er 3+ :silica fiber amplifier is a three-level system. 3 32 pump 2 1.55 m • Pumping at 980 nm using InGaAs laser diodes; a mixture of homogeneous/inhomogeneous broadening; ~ 5.3 THz 1 • The laser transition can also be directly pumped at 1.48 m by light from InGaAsP laser diodes – like a quasi-two-level scheme 62 62
Four-level systems pump h p Nonradiative relaxation Nonradiative relaxation h |3> |2> |1> |0> A four-level system is more efficient than a three-level system. The lower laser level |1> lies sufficiently high above the ground level |0>, with E 10 >> k B T. Thus, in thermal equilibrium, the population in |1> is negligibly small compared with that in |0>. Pumping takes place from level |0> to level |3>. 63
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Lecture 8: Laser amplifiers Opt
Page 3 and 4:
Optical transitions 3
Page 5 and 6:
Photon-matter interaction processes
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
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: Three-level systems The parameter
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 and 106: Gain coefficients This represents t
Page 107 and 108: Amplified spontaneous emission T
Page 109: Amplifier noise The ASE of a la
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Lecture 8: Laser amplifiers

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