Experiment on acousto-optic modulation effect with red laser

The proposed experiments are pedagogically rich as they allow not only to study the different physical phenomena involved in acousto-optic interaction but also to provide an overview of potential applications in both intensity modulation and deflection.

Acousto-optic systems are or have been used in many fields: laser printer, scanner, projection, pulsed laser, tunable filters, etc ...

An equivalent product is presented in the chapter dedicated to waves: it involves an interaction between an optical wave and an acoustic network generated by ultrasonics in a liquid.

Topics covered:
- Bragg cell / Determination of Bragg diffraction angle
- Study of diffracted beams as a function of the acoustic wave frequency
- Evaluation of the speed of the acoustic wave in the material
- Measurement of diffraction intensity as a function of the acoustic wave power
- Calculation of diffraction efficiency and medium absorption
- Study of acousto-optic modulation and application to audio signal recording and transport on an optical carrier
- Study of acousto-optic deflection and application to projection and optical addressing

Principles and objectives:
The acousto-optic effect involves the interaction between an ultrasonic wave and an optical wave in a solid or liquid medium. The acoustic wave causes the propagation of a deformation and consequently a variation in the refractive index in the medium. The acoustic wave is generated, for example, by a piezoelectric transducer. The refractive index variation has spatial and temporal periodicity. The index network moves parallel to itself at the speed of the acoustic wave. Since this speed is much lower than that of light, the acoustic wave can be considered as stationary and the network fixed with respect to the incident light beam. The refractive index network formed by acousto-optic interaction is then used to cause the diffraction of an optical wave.

Composition:
▪ 1 prismatic bench of 1 m with adjustable feet set (ref.202519)
▪ 2 standard prismatic riders (ref.202234)
▪ 1 prismatic rider with angular adjustment (ref.202514)
▪ 1 optical foot (ref.203212)
▪ 1 red laser diode (ref.202721)
▪ 1 polarizer in graduated mount (ref.202374)
▪ 1 acousto-optic modulator/deflector (Bragg cell)
▪ 1 control power supply for acousto-optic cell
▪ 1 object-holding plate with horizontal adjustment
▪ 1 amplified detector with adjustable gain (ref.204888)
▪ 1 white and gridded metal screen 20x20 cm (ref.202368)
▪ 1 digital CCD/CMOS sensor + OD1, OD3 filters, polarizer + software (ref.204354)
▪ 1 multimedia kit (radio + speakers + all necessary connections for proper functioning)
▪ 1 experiments manual