Lecture 18 Review Spr 2010

Lecture 18 Review Spr 2010 - Review Spring 2010 Mat 288S...

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Spring 2010 Mat 288S Optoelectronic Measurements 1 Review
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The Geometrical Extent Spring 2010 2 Mat 288S Optoelectronic Measurements
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Power Throughput Source Spectral Radiance L (W-m -2 -sr -1 -nm -1 ) Aperture A (m 2 ) Solid angle Ω (sr) = π• NA 2 Transmittance T Geometrical Extent G = A Ω Flux across element Φ = TGL Spring 2010 3 Mat 288S Optoelectronic Measurements
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Gaussian Beam Distribution = ) ( 2 exp ) ( 2 2 0 z r I r I ω = 2 2 2 exp 1 ) ( ) ( r P r P Power enclosed within circle of radius r: Spring 2010 4 Mat 288S Optoelectronic Measurements
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Beam Waist and Divergence + = 2 2 0 1 ) ( z z z R λ πω 2 / 1 2 2 0 0 1 ) ( + = ω z z 0 θ = = z 0 ) ( z z z z R ) ( For large z : Spring 2010 5 Mat 288S Optoelectronic Measurements
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Beam Focusing Spot diameter NA f lens λ ππ ω 2 2 2 0 = Example f=10 mm, 2 ω lens =5 mm, λ =1.55 μ m, spot diameter=3.9 μ m Spring 2010 6 Mat 288S Optoelectronic Measurements
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Time Domain – Frequency Domain Bandwidth 35 . time Rise = Spring 2010 7 Mat 288S Optoelectronic Measurements
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Responsivity and Quantum Efficiency R( λ ) = Amps / Incident Watt Q( λ ) = e - / Incident Photon Q h q R υ = Spring 2010 8 Mat 288S Optoelectronic Measurements
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Photodiode Biasing Reverse bias improves time response and linearity Reverse bias induces “dark” current, which then leads to excess shot noise Unbiased operation requires small load resistance for linearity, but then requires amplification for adequate signal amplitude In practice, transimpedance amplifiers are used: 10 3 –10 8 for low level detection 10 2 -10 3 for high speed operation Spring 2010 9 Mat 288S Optoelectronic Measurements
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Photovoltaic Operation I p P 0 P 1 P 2 P 3 V I Small R L Large R L Spring 2010 10 Mat 288S Optoelectronic Measurements
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Photoconductive Operation P 0 P 1 P 2 P 3 V I Small R L Large R L I p + - Spring 2010 11 Mat 288S Optoelectronic Measurements
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This note was uploaded on 02/02/2011 for the course ECE 227A taught by Professor Coldren during the Spring '08 term at UCSB.

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Lecture 18 Review Spr 2010 - Review Spring 2010 Mat 288S...

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