Acousto-Optical Effects (Ultrasonic Experiment Set 8).

Identifying interactions between a mechanical wave and light, also known as acousto-optic effects (AOM, acousto-optic modulation)

This set was put together for some challenging experiments dealing with the interactions between a mechanical wave and light (the acousto-optic effects: AOM, acousto-optic modulation).The experiments promote knowledge and understanding of the propagation properties of both mechanical and electromagnetic waves. It is shown that the density changes caused by the compression and dilation of an ultrasonic wave cause a change in the refractive index of the medium. The resulting grating causes the diffraction of laser light. In addition, the intensity modulation and the wavelength change of laser light are demonstrated. In various experiments, the diffraction properties of light on standing and traveling ultrasonic waves are investigated and measured. The speed of sound in various liquids is determined by varying the interference maxima of the laser light at different ultrasonic frequencies (resonance cell).Using a photodiode, the amplitude modulation and phase shift of laser light on a standing wave can be displayed and recorded with an oscilloscope. The change in frequency of the sound wave influences the amplitude modulation and allows the speed of sound in the medium to be calculated. The difference between the diffraction of standing and moving waves is demonstrated using an absorber mat, which prevents the formation of standing ultrasonic waves in the sample tank. A frequency shift of the laser light caused by the Doppler effect can be measured on the moving ultrasonic wave. By using beam splitters and mirrors, differently diffracted light components are caused to interfere. The resulting beats are displayed and measured using the oscilloscope.
This experiment set is suitable both for demonstrating acousto-optical effects and their application in technology, and for carrying out interesting experiments in student internships for advanced students in all scientific and technical disciplines.

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