A waveplate controls the polarization of light by causing a phase shift in polarized light. A quarter wave plate transforms linearly polarized light into circularly polarized light and is used in imaging, laser, semiconductor, and aerospace applications. Quartz is often used as a retardant material, and other materials like mica, magnesium fluoride, and sapphire can also be used. Quarter wave plates are used to control the power level of lasers, add optical isolation, and analyze body fluids. Different types of retarders can be used to meet application requirements.
A waveplate is a device used to control the polarization of light. When light is polarized, it is directed in two axes; the angle between the axes, one designated fast axis and the other slow axis, is 45°. A quarter wave plate transforms linearly polarized light into circularly polarized light and does the reverse as well. Waveplates in general work by causing a phase shift in polarized light, so that the refractive index is different on each axis. Various materials are used to make a quarter wave plate, which is typically used in imaging, laser, semiconductor and aerospace applications.
When a quarter wave plate is used, it is positioned so that fast and slow light waves are equally manipulated. A polarized light wave is oriented at a 45° angle to one of the wave’s axes. The quarter wave plate is physically designed to produce a phase difference of one quarter wavelength. Multiples of this increment can also be accommodated by multiple order waveplates.
The wavelength of light in the application and the size of the waveplate are important in choosing the right device. A quarter wave plate operates on the concept of retardation and quartz is often used as a retardant material. Quartz components are tough enough to be used with lasers and are usually coated with an anti-reflection material to transmit the most light. They are also manufactured to specific thicknesses and other characteristics by polishing. Other materials sometimes used are mica, magnesium fluoride and sapphire.
Quarter wave plates are used to control the power level of lasers and to add optical isolation. They are also used in medical laboratory equipment to help analyze body fluids. Generally used wherever polarized light needs to be controlled, waveplates are also often found in astronomical and aerospace equipment. A variety of materials may comprise a quarter wave plate and the use of crystalline or polymeric materials depends on the application.
Application requirements can be met by using different types of retarders in a quarter wave plate. Quartz retardants, for example, are selected based on bandwidth and desired thermal performance. There are various multiple order retarders and zero order retarders depending on these needs. A quarter wave achromatic plate has materials that have a better field of view and are more accurate in terms of their wavelength range. Selecting a corrugated plate requires knowing the best specification for the application; an understanding of optics is also beneficial.
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