kvartbølgeplate

A kvartbølgeplate, also known as a quarter-wave plate, is an optical component that alters the polarization state of light. It is a type of wave plate or retarder that introduces a phase difference between the two orthogonal components of polarized light. Specifically, a kvartbølgeplate is designed to induce a phase shift of π/2 radians (or 90 degrees) between the extraordinary and ordinary rays.

This phase shift is achieved by utilizing birefringent materials, which have different refractive indices for light polarized parallel to different axes. The thickness of the kvartbølgeplate is precisely controlled so that the difference in optical path length for the two polarization components, when light travels through it, results in the desired π/2 phase difference. When linearly polarized light with its polarization direction at an angle of 45 degrees to the optical axes of the kvartbølgeplate enters the plate, it is converted into circularly polarized light. If the incident light is already circularly polarized, it will emerge as linearly polarized light.

Kvartbølgeplater find numerous applications in optics. They are commonly used in polarimetry to measure the polarization of light, in optical isolators to prevent back reflections, in displays to control polarization for liquid crystal devices, and in various scientific instruments for manipulating and analyzing polarized light. Their ability to transform polarization states makes them essential components in many optical systems.