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Amplitude Modulators

Amplitude Modulators
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New Focusՙ amplitude modulators arespecifically designed for high performance at modulation frequencies of up to 200 MHz.The Model 4102/4 broadband amplitude modu-lator can be operated from DC to 200MHz. TheModel 4101/3 is a resonant device that can be built to operate at any frequency from 0.01to 200MHz.The crystals in these modulators are mounted at45so that your input polarization can be either vertical or horizontal. To minimize thermalbirefringence, we use two matched crystalsarrangedin series. This results in amplitudemodulators that exhibit less than 1mrad/аC of temperature-dependent polarization rotation.Since our modulators dont include externalpolarizers, they can be used as electronically variable wave plates. Touse the device as an amplitude modulator,apolarizer is needed at the output. (See page 75 for our polarizers.)The Model 4101/3 can be driven with a low-voltage function generator or the Model 3363 resonant-modulator drivers(page 72). The Model 4102/4 can be driven using our Model3211 broadband-modulator drivers (page 70) with a function generator. Call us or visit the support section of our website for driver recommendations. > Attenuating a laser beam with a Model 4104 amplitude modulator. The beampasses through the modulator followed by a polarizer (page 75). A Model 3211 broadband-modulator driver is used to drive the modulator. Extinction Ratio > The extinction ratio of an amplitude modulator is the ratio between the optical power at maximum and minimum transmission. A high extinction ratio indicates a good modulator. For our Model 410X modulators, the extinction ratio is limited by refrac- tive-index distortions in the electro-optic crystalsthat impart wavefront distortion to the optical beam. For these devices, the on:offextinction ratio is typically 50:1 for a 0.5-mm-diameter beam. Higher values can be achieved by focusing your beam. TechnicalNote

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