Waveplates (also known as retarders) are  optical components used to transmit light, changing the polarization without deviating, attenuating or displacement of the beam. Waveplates are made of birefringent crystal such as quartz, calcite or mica with precise thickness. The optical axis is parallel to the crystal surface, it can abtain the corresponding phase retardance by selecting different thicknesses of crystal.
When the linear polarized light passes through the half-wave plate, the transmitted light is still linear polarizing light,  the vibration direction of the transmitted light will rotate  2θfrom the original orientation ( θ is the angle between the incident light and the crystal optical axis ), When the linear polarized light passes through 1/4 waveplate at a 45°, the transmitted light will change from linear polarized to circularly polarized light.

• MaterialQuartz Crystal
• Parallelism＜1 arcsec
• Diameter Tolerance+0/-0.1mm
• Surface Quality20/10
• Retardance Toleranceλ/500
• Wavefront Aberrationλ/8@633nm
• Clear Aperture CA (mm)Center90%
• AR CoatingR＜0.2%@Designed Wavelength