Cemented plates can delaminate. Contacted plates drift. Air spacing removes both failure modes — and improves alignment accuracy.
For 10 mm to 50.8 mm clear apertures at laser wavelengths from 237 nm to 2021 nm, an air-spaced zero-order plate is the default we recommend to laser and telecom customers. If your power level or wavelength is unusual, send us the numbers — laser damage testing is available.
What you gain
Higher thermal stability — retardation barely moves with temperature
Both change the polarization of light. Only one stays accurate when your lab warms up. Here is the difference in plain terms.
Tunable laser or wide spectrum? A single material can't hold retardation across hundreds of nanometers. Two materials can.
An uncoated glass surface eats 4% of your beam. Coatings decide what happens to the rest — and how much power they can survive.
