Multiple-Order Quartz Wave Plates

Our multiple-order wave plates are crystal quartz optics designed to differentially retard the phase of a polarized beam. With the proper phase shift, the half waveplate can rotate the direction of polarization. For half waveplates, the amount of polarization rotation is twice the amount of waveplate rotation. We offer dual wavelength multiple-order wave plates in addition to our standard single wavelength versions.

Quarter-wave plates are used to turn plane-polarized light into circularly polarized light and vice versa. To do this, we must orient the wave plate so that equal amounts of fast and slow waves are excited. We may do this by orienting an incident plane-polarized wave at 45° to the fast (or slow) axis, as shown.

When using multiple-order wave plates, several items should be considered. A wave plate of practical thickness produces a multiple of λ/4 or λ/2 retardation (e.g. 15 1/2 λ for a ~1mm thick optic). Higher orders cause retardation to vary dramatically with change in wavelength.

Wave plates are sensitive to temperature changes. A typical multiple-order wave plate has a temperature coefficient of 0.0015λ/°C, compared to 0.0001λ/°C for a zero-order wave plate, so tighter temperature control will be required.

Quartz is an example of a uniaxial crystal, or crystal in which one axis has a different refractive index than the other two axes. The index associated with the unique axis is called the extraordinary index, the ordinary refractive index is associated with the remaining two axes. A waveplate is a polished slice of a uniaxial crystal, in which the extraordinary axis lies within the plane of the optic. Light with polarization vector components oriented along the ordinary axis will undergo a phase delay relative to the perpendicular component oriented along the extraordinary axis. Change in polarization state will depend on the input state, and the physical orientation of the waveplate.