Quarter Waveplate

What is quarter waveplate?

A quarter-wave plate is an optical phase retarde, It is typically made of quartz. Its core function is to cause a π/2 (i.e., 90° or 1/4 wavelength) phase difference between two polarized light beams passing through it, where the vibration directions of the light are perpendicular to each other (ordinary light o-light and extraordinary light e-light).This property enables the quarter-wave plate to change the polarization state of light, for example, converting linearly polarized light to circularly polarized light or elliptically polarized light, and vice versa. When the vibration direction of the incident linearly polarized light forms an angle of ±45° with the fast axis (or slow axis) of the wave plate, circularly polarized light can be obtained.

Specifications

By taking advantage of the properties of the quarter-wave plate, it can be combined with other polarizing optical components to achieve various functions.

Circular Polarizer

A quarter-wave plate can convert linearly polarized light into circularly polarized light. A circular polarizer can be constructed by using a linear polarizer and a quarter-wave plate.

Optical Attenuator

A quarter-wave plate can be used to change the polarization direction of polarized light, so a combination of a polarizer and a quarter-wave plate can be used to build an optical attenuator

Optical Isolator

Principle Explanation: The laser beam emitted by the laser source is incident vertically onto a polarization beam splitter cube, exiting as linearly polarized light in the vertical polarization direction (P-polarized light). This P-polarized light then enters a quarter-wave plate, where it is converted into left-handed circularly polarized light (or right-handed circularly polarized light). The right-handed circularly polarized light (left-handed circularly polarized light) reflected back in the optical path enters the quarter-wave plate again and is converted into linearly polarized light in the horizontal polarization direction (S-polarized light). The S-polarized light is then reflected by the polarization beam splitter cube towards another direction.

Polarization Generator

The laser beam is emitted by the laser source. The laser is incident perpendicularly onto the polarizer. The polarizer can modulate the incident light into linearly polarized light. The modulated linearly polarized light is then incident onto the half-wave plate. The polarization direction is deflected. The light emerging from the half-wave plate is then incident onto the quarter-wave plate. When the quarter-wave plate has the same polarization direction as the linearly polarized light incident on it, the emergent light is linearly polarized. At this time, the half-wave plate can be used to adjust the polarization direction. When the fast axis direction is not consistent with the polarization direction, the emergent light is elliptically polarized or circularly polarized. At this time, the quarter-wave plate can be used to adjust the ellipticity and rotation direction. By using this combination, any polarization state can be output.