Air spaced etalons reduce the temperature dependence problem by
using air as the etalon medium, to greatly reduce the change in
refractive index with temperature. The mirror spacing is now determined
by spacers that may still be made from Fused Silica or by even more stable materials
such as ULE or Zerodur. Air spaced etalons are significantly more complex
since there are now three components involved, two end mirrors and the spacer.
The outside surfaces of the end mirrors also need to be wedged and AR coated to
avoid reflections from these surfaces causing additional unwanted etalon
effects.
Item
Specifications
Material
Schott Zerodur, Corning ULE or Fused Silica
Dimension
~5×5×6mm（Specified by customer）
Dimension tolerance
±0.1mm
Parallelism
＜1″
Clear aperture
90%
Surface quality
MIL 20-10
Surface flatness
λ/20 ＠632.8nm
FSR
25,50,100,200 GHZ
FSR tolerance
土0.01G for 50-100GHZ/土0.02G for 100-200GHZ or specified by customer