Kvartvågslager

A kvartvågslager, often translated as quarter-wave plate or quarter-wave retarder, is an optical element that splits a linearly polarized light beam into two circularly polarized beams. It achieves this by introducing a phase difference of 90 degrees, or one-quarter of a wavelength, between the two components of the polarized light. This phase difference is created by using a birefringent material that has different refractive indices for light polarized parallel and perpendicular to its optical axis.

The thickness of the kvartvågslager is carefully chosen to correspond to a quarter of the wavelength of the light it is designed to operate with. When linearly polarized light enters the kvartvågslager at a 45-degree angle to its optical axis, it can be decomposed into two equal components, one parallel and one perpendicular to the axis. As these components travel through the birefringent material, their speeds differ, leading to a phase shift. Upon exiting the kvartvågslager, these components recombine to form either left- or right-circularly polarized light, depending on the orientation of the input polarization and the optical axis.

Kvartvågslager find applications in various optical systems. They are used in polarimetry to measure the polarization state of light, in optical isolators to prevent unwanted reflections, and in displays and imaging systems where manipulation of polarization is required. They are also crucial components in some types of lasers and for creating specific optical effects. The specific material and dimensions of a kvartvågslager are tailored to the wavelength range of operation.

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