Interference Filters in Refl ection

22 Mar 2018

Interference filters are widely used in a transmissive configuration, whereby light passes

through the filter to cause some effect, be that band-pass, short-pass or long-pass etc. By

nature, interference filters do not generally absorb in the visible-NIR, but instead light is

either transmitted or reflected. The makes transmissive interference filters ideal for applications

within this spectral range.

Things become more difficult however when high transmission is required in either the UV

or IR, where the intrinsic properties of materials cause them to absorb certain wavelengths.

For such situations it is possible to use a number of interference filters in reflection to isolate

the desired wavelengths by taking advantage of high reflectivity without the absorption

associated with transmissive filters.

A variety of configurations are available which can either maintain the optical axis or steer

the beam in a chosen direction. Another area in which this method excels is creating

narrow notch rejection filters. A narrow notch filter in transmission is notoriously difficult

to produce, particularly when a high OD is required in the rejection band. LASER COMPONENTS‘

partners Omega Optical can now use their industry leading high transmission

narrow bandpass filters in refl ection to create very narrow notches.