piezooptic

The term piezooptic refers to the piezo-optic (stress-optic) effect, which is the change in a material’s optical properties, especially its refractive indices and birefringence, produced by mechanical stress. When transparent solids are stressed, their optical response alters in a way that depends on the material and the direction of light. The effect is commonly described by the stress-optic law, which relates changes in the refractive index to applied stress through piezo-optic coefficients: Δ(1/n^2) = p_ijkl σ_jk. In isotropic materials this reduces to a simpler scalar relation between Δn and the applied stress. The coefficients are material- and orientation-dependent, and they determine how light polarization is affected.

In practice, the piezo-optic effect is often driven by the piezoelectric response of a material. An electric field in a piezoelectric crystal generates mechanical strain, which induces birefringence via the elasto-optic mechanism. This combination enables piezo-optic modulators, where an electrical signal controls the optical retardation or polarization state of light by producing controlled stress in a crystal.

Materials commonly used to exploit the piezooptic effect include quartz, lithium niobate, and lithium tantalate, among others. These materials can be fashioned into devices that modulate light or serve in polarization control, sensing, or imaging systems. The broader field of photoelasticity uses the piezooptic effect to analyze and measure internal stresses by observing polarization changes in light passed through stressed samples. While the strength of the effect varies, the piezooptic phenomenon provides a versatile means to link mechanical and optical properties in transparent solids.