April 13, 2016 -
Sophisticated monitor and deposition methods enable multi-cavity narrowband filters that push the envelope of performance.
Hard coated ultra-narrowband optical filters made using modern plasma processes offer much improved transmission, temperature stability and out of band blocking as compared to legacy soft coatings. These filters are used in optical systems as diverse as LIDAR (light detection and ranging), Doppler shift detection of plasma velocity, laser cleanup, chemical and gas sensing, as well as for cutting-edge astronomy and instrumentation applications.
Ultra-narrowband filters exhibiting square passbands for the NIR were pioneered during the telecom industry in the 1990’s but, until recently, have not been viable in large format sizes. Larger filters can be demanding to manufacture due to uniformity constraints, but are highly sought after for instrumentation purposes. Narrowband filters with compulsory operation in the Visible and UV present an added challenge due to loss and scatter; the deposition control system must be adept to deal with lower levels of light used for optical monitoring.