Optical Contacted Zero Order Waveplates, a quarter-or half-wave retarder made from two plates of quartz with their fast axes crossed; the difference in thickness between the two plates determines the retardance. Zero-order retarders provide accurate retardance over a broad range of wavelengths and dance over a broad range of wavelengths and are more durable than single-element retarders. Because it is optical contacted, the damage threshold should be as good as single plate (about 10MW/cm2).
| ATTRIBUTE | SPECIFICATIONS |
| material | Crystal Quartz |
| wavefront distortion | +0.0, -0.1mm |
| PARALLEL FOCAL LENGTH TOLERANCE | λ/4@632.8mm |
| retardation tolerance | λ/500 |
| wavelength range | 400-2100nm |
| parallelism | < 1 arc second |
| SURFACE FIGURE: IRREGULARITY(N) | <0.5 fringe |
| SURFACE QUALITY | 20/10 scratch and dig |
| COATING | With AR coating on outside surfaces |
