Ch6Sec1 - Joseph C. Palais 6.1 6 The released energy takes...

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THE FIBER FORUM Fiber Optic Communications JOSEPH C. PALAIS PRESENTED BY
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Joseph C. Palais 6.1 2 Chapter 6 Optical Sources and Amplifiers
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Joseph C. Palais 6.1 3 Section 6.1 Light-Emitting Diodes An LED is a pn junction semiconductor. It emits light in the infrared or visible spectrum when forward biased. p n LED i V + -
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Joseph C. Palais 6.1 4 LIGHT EMITTING DIODES p n Energy Level Diagram for V = 0 (zero bias) W g Conduction Band Valence Band - - - - - - - + + + + + + Hole Energy Electron Energy
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Joseph C. Palais 6.1 5 P N Energy Level Diagram for V > 0 (forward bias) W g Conduction Band Valence Band - - - - - - - - - - - - - - - - - - - - - - - + + + + + + + + + + + + Hole Energy hf = W g Electron Energy W g = bandgap energy Its value depends on the semiconductor used. LIGHT EMITTING DIODES
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Unformatted text preview: Joseph C. Palais 6.1 6 The released energy takes the form of a photon.-19-34 1 1.6 10 , 6.626 10 eV J h J s = = (6.1) hf W g 2245 g W c h = c h W g = LIGHT EMITTING DIODES Now W g is in joules and is in meters Joseph C. Palais 6.1 7 Suppose W g is given in eV. Compute the output wavelength. 1.24 g W = (6.2) with W g in eV and in m. LIGHT EMITTING DIODES 34 8 19 6.626 10 (3 10 ) ( ) 1.6 10 g g hc W W eV --= = 6 1.24 10 ( ) g m W eV-= Joseph C. Palais 6.1 8 Material ( m) W g (eV) GaAs 0.9 1.4 AlGaAs 0.8 - 0.9 1.4 - 1.55 InGaAs 1.0 - 1.3 0.95 - 1.24 InGaAsP 0.9 - 1.7 0.73 - 1.35 GaInP 0.64 - 0.68 1.82 - 1.94 Common Characteristics LIGHT EMITTING DIODES...
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Ch6Sec1 - Joseph C. Palais 6.1 6 The released energy takes...

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