GOLD provides transmittance filters with these features:
- Peak wavelength can be selected at wavelengths of 120 nm and longer.
- Bandwidth can be selected with FWHM of ~ 10 nm and wider
- Long-wavelength rejection can be selected up to the range of ~ 10-6.
The filters are made with multilayers of Al/MgF2 or Al/AlF3.
The transmittance at the peak wavelength is very dependent on the long-wavelength rejection and on the bandwidth. A larger rejection of the long wavelengths results in a smaller peak transmittance. A narrower band often results in a smaller peak transmittance, but also in a larger long-wavelength rejection.
Here are two examples of filters with a strong rejection of the visible.
Filter peaked at 132 nm with a FWHM of 15.2 nm
Filter peaked at 155 nm with a FWHM of 17.6 nm