lect23-24

lect23-24 - Electro-Optic Modulators and Effects EO...

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Electro-Optic Modulators and Effects EO Amplitude Modulator EO Phase Modulator
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EO Amplitude Modulator EO Phase Modulator Industry Standards: ThorLabs “Applying an electric field to the crystal induces a change in the indices of refraction (both ordinary and extraordinary) giving rise to an electric field dependent birefringence which leads to a change in the polarization state of the optical beam.” - ThorLabs “The input beam is linearly polarized along the vertical direction which is the Z-axis of the crystal. A voltage at the RF input is applied across the Z-axis electrodes inducing a change in the crystal's extraordinary index of refraction thereby causing a phase shift in the optical signal.” - ThorLabs
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Electro Optic Effect • EO Effect: change in the optical properties of a material in response to a slow-varying electric field E – Refractive index n change • EO Effects: n E linear electro-optic effect / Pockels effect n E 2 quadratic electro-optic effect / Kerr effect (gases, liquids – centrosymmetric)
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Electro Optic Effect Lens of controllable focal length Prism with controllable beam-bending capability (optical scanning device) Optical phase modulator: Transparent plate of controllable refractive index Retarder of controllable retardation: Anisotropic crystal with changeable refractive indexes Optical intensity modulator Optical switch
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Electro Optic Modulators • EO Modulator: Optical device in which a signal- controlled element displaying an EO Effect is used to modulate a beam of light – Frequency – Amplitude –Phase – State of Polarization (SOP) – Propagation Direction
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Review of Polarization (Special Cases) Uniform plane wave propagating in the +z direction: E = a x E x cos( ω t + φ x ) + a y E y cos( ω t + φ y ) State of Polarization (SOP): evolution of the electric field vectors in t For linearly polarized waves (LP) , φ x = φ y = φ E = ( a x E x + a y E y ) cos( ω t + φ ) E vector traces a straight line
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lect23-24 - Electro-Optic Modulators and Effects EO...

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