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Ch4_StimulatedEmissionDevicesLASERS

Ch4_StimulatedEmissionDevicesLASERS - Stimulated Emission...

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1 901 37500 光電導論 Stimulated Emission Devices: LASERS Kasap Chapter 4 2 901 37500 光電導論 Contents 4.1 Stimulated Emission and Photon Amplification 4.2 Stimulated Emission Rate and Einstein Coefficients 4.3 Optical Fiber Amplifiers 4.4 Gas Laser 4.5 The Output Spectrum of Gas Laser 4.6 Laser Oscillation Conditions 4.7 Principle of the Laser Diode 4.8 Heterostructure Laser Diodes 4.9 Elementary Laser Diode Characteristics 4.10 Steady State Semiconductor Rate Equation 4.11. Light Emitters for Optical Fiber Communications 4.12 Single Frequency Solid State Lasers 4.13 Quantum Well Devices 4.14 Vertical Cavity Surface Emitting Lasers (VCSELs) 4.15 Optical Laser Amplifiers 4.16 Holography 3 901 37500 光電導論 4.1 Simulated Emission and Photon Amplification 4 901 37500 光電導論 E 1 E 2 h υ (a) Absorption h υ (b) Spontaneous emission h υ (c) Stimulated emission In h υ Out h υ E 2 E 2 E 1 E 1 Absorption, spontaneous (random photon) emission and stimulated emission. Spontaneous emission: random direction E 1 is empty As if e - is oscillating in freq. v Stimulated emission: induced Two photons are in phase, same direction same polarization, same energy Incoming e - couples to the e - in E 2 Basis for photon amplification Re-absorbed? => population inversion not in two level systems Fig. 4.1 (in steady state: R 12 = R 21 ) Optical Cavity feedback high optical intensity
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