Ultrasteep edge filters are used, among others, for Raman applications in the range from 442 nm to 1064 nm. Depending on the wavelength range, transitions below 3 nm can be achieved. The blocking lies at OD6 and the transmittance is above 90%.

These edge filters are available as short-pass filters and long-pass filters.
As short-pass filters, for example, laser light with wavelengths above 532 nm is reduced by a factor of millions while at the same time at least 90% of the light from 350 nm to 529 nm are allowed to pass through.
The long-pass version has the opposite effect: wavelengths below 532 nm are attenuated millions of times. At the same time, the edge filter allows at least 90% of the light from 535 nm to 1200 nm to pass.

This allows spectroscopic instruments to distinguish and effectively separate the excitation wavelengths from the emitted wavelengths without negatively affecting the desired wavelengths.