When ultrasound waves travel in a medium, the medium is subject to elastic strain with periodic changes in both time and space, causing a similar periodical change in the refractive index of the medium. As a result, when a ray of light passes through a medium in the presence of ultrasound waves in the medium, it is diffracted by the medium acting as a phase grating. This is the basic theory of acousto-optic effect.
Acousto-optic effect is classified into normal acousto-optic effect and anomalous acousto-optic effect. In an isotropic medium, the plane of polarization of the incident light is not changed by the acousto-optic interaction (called normal acousto-optic effect); in an anisotropic medium, the plane of polarization of the incident light is altered by the acousto-optic interaction (called anomalous acousto-optic effect). Anomalous acousto-optic effect provides the key foundation for the fabrication of advanced acousto-optic deflectors and tunable acousto-optic filters. Unlike normal acousto-optic effect, anomalous acousto-optic effect cannot be explained by Raman-Nath diffraction. However, by using parametric interaction concepts such as momentum matching and mismatching in nonlinear optics, a unified theory of acousto-optic interaction can be established to explain both normal and anomalous acousto-optic effects. The experiments in this system only cover normal acousto-optic effect in isotropic media.
Experiment Examples 1. Observe Bragg diffraction and measure Bragg diffraction angle 2. Display acousto-optic modulation waveform 3. Observe acousto-optic deflection phenomenon 4. Measure acousto-optic diffraction efficiency and bandwidth 5. Measure the traveling velocity of ultrasound waves in a medium 6. Simulate optical communication using acousto-optic modulation technique Specifications|
Description |
Specifications |
| He-Ne Laser Output | <1.5mW@632.8nm |
| LiNbO3 Crystal | Electrode: X surface gold plated electrode flatness <λ/8@633nmTransmittance range: 420-520nm |
| Polarizer | Optical aperture Φ16mm /Wavelength range 400-700nmPolarizing degree 99.98%Transmissivity 30% (paraxQllel); 0.0045% (vertical) |
| Detector | PIN photocell |
| Power Box | Output sine wave modulation amplitude: 0-300V continuous tunableOutput DC bias voltage: 0-600V continuous adjustable output frequency: 1kHz |
| Optical Rail | 1m, Aluminum |