A zero-order achromatic wave plate can be built by aligning the fast axis of a multi-order crystalline quartz wave plate with the slow axis of a magnesium fluoride wave plate, where the optical path length difference between the two wave plates is either λ/4 or λ/2. The use of crystalline quartz and magnesium fluoride allows the dispersive effects to be minimized so that a nominally flat spectral response is achieved over the operating range of the achromatic wave plate. The achromatic wave plates are constructed by placing an etched stainless steel spacing ring between the two multi-order wave plates and epoxying these three pieces together; then the achromatic wave plate assembly is placed into a threaded Ø1" anodized aluminum housing and held in place using an O-ring. It should be noted that the epoxy is only applied outside of the clear aperture in order to prevent the damage threshold from decreasing. The wave plate housing is engraved with a line indicating the orientation of the fast axis of the wave plate and engraving that identifies the spectral operating range of the wave plate as well as whether it is a λ/4 or λ/2 wave plate. For further information on using and selecting a wave plate, please see our Selection Guide Tab. In addition, Thorlabs also offers Zero-Order Wave Plates, Telecom Zero-Order Wave Plates, Monochromatic Multi-Order Wave Plates, Dual Wavelength Multi-Order Wave Plates, and a complete line of Polarization Optics.