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7 March 2014 A novel acousto-optic modulation-deflection mechanism using refractive index grating as graded index beam router
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Proceedings Volume 8982, Optical Components and Materials XI; 89821T (2014)
Event: SPIE OPTO, 2014, San Francisco, California, United States
A novel acousto-optic modulation mechanism will be addressed in this paper. Focused Gaussian beam passing through acousto-optic media experiences different refractive index regions arising from acoustic waves generated by ultrasonic source. In this way according to the snell’s law of refraction the beam propagation path will be altered when these periodic traveling waves reach the incoming radiation where a typical p-n junction photodiode located inside the rising or falling lobe of the undiffracted Gaussian beam senses these small lateral deflections. Due to small variations of the refractive index the magnitude of deflection will be up to tens of micron outside the modulator. Hence, sharp intensity gradient is required for detecting such small beam movements by appropriate lens configuration to focus the Gaussian profile on the detector junction area. In the other words intensity profile of zero order beam oscillates proportional to the time dependent amplitude of the acoustic waves versus previous methods that intensity of diffracted beam changes with applied ultrasonic intensity. The extracted signal properties depend on the beam collimation, quality of beam profile and depth of focus inside the modulator. The first experimental approach was proceeded using a collimated 532 nm diode laser source (TEM00), distilled water as interaction media and 10 MHz transducer as ultrasonic generator where a cylindrical glass column with input-output flat windows was used for liquid support. The present method has advantages over common acoustooptical techniques as low cost, simplicity of operation, direct modulation of the signal and minimum alignment requirement.
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Alireza Jangjoo, Mohammad Reza Baezzat, and Ahmad Razavizadeh "A novel acousto-optic modulation-deflection mechanism using refractive index grating as graded index beam router", Proc. SPIE 8982, Optical Components and Materials XI, 89821T (7 March 2014);

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