Structure

Tetragonal, P4₁2₁2

Melting Point

730ºC

Density

5.99 g/cm³

Mohs Hardness

4.5

Photo-elastic Coefficient at 632.8nm

P₁₁ =0.074、P₁₃ =0.340
P₃₁ =0.091、P₃₃ =0.241

Figure of Merit

793 x10^-18S³/g

Transmittivity

>70 % at 632.8nm

Refractive Index at 632.8nm

n_o=2.55、n_e =2.142

Gradient of Refractive Index

≤5 x10^-5/cm

Phase Velocity (Transverse Wave[110]-Propagation)

616 m/s

Wavefront distortion

less than l/8 @ 633nm

Dimension tolerance

(W ± 0.1mm) x (H ± 0.1mm) x (L + 0.2mm/-0.1mm)

Clear aperture

> 90% central area

Flatness

l/8 @ 633nm

Scratch/Dig

10/5 to MIL-O-13830A

Parallelism

better than 20 arc seconds

Perpendicularity

5 arc minutes

Angle tolerance

qD < ± 0.5°, fD < ±0.5°