Achromatic waveplates are similar to zero-order except that the two plates are made from different materials, such as crystal quartz and magnesium fluoride. Since the dispersion of the birefringence can be difference for the two materials, it is possible to specify the retardation value at a wavelength range. Hence, the retardation of the resulting waveplate can be made to low sensitivity to wavelength change.
Based on the contact methods of the two plates, achromatic waveplates are classified into two types: air-spaced and cemented.
| ATTRIBUTE | SPECIFICATIONS |
| material | Crystal quartz and MgF2 |
| DIAMETER TOLERANCE | +0.0, -0.1mm |
| wavefront distortion | λ/4@632.8mm |
| retardation tolerance | λ/100 |
| wavelength range | VIS: 465-610nm, NIR: 700-1000nm, IR: 1200-1650nm |
| parallelism | < 10 arc second |
| SURFACE FIGURE: IRREGULARITY(N) | <0.5 fringe |
| SURFACE QUALITY | 20/10 scratch and dig |
| COATING | With AR coating on outside surfaces |
