© 2011 Thorlabs
153Appendix
One surface of these reflective type ND Filters is metallized to obtain the 20 dB and
40 dB loss, respectively. The rear side of this fused silica substrate needs to be anti
reflective coated to prevent interference effects due to multiple reflections. Therefore,
the quality of this AR coating is important for a good image quality.
The displayed curve shows the remaining reflectivity of the AR coating supplied on
the fused silica substrate. Between 220 nm and 340 nm is below 0.25 %.