An atomic line filter (ALF) is an advanced optical band-pass filter used for the filtering of electromagnetic radiation with precision, accuracy, and minimal signal strength loss. Atomic line filters work via the absorption or resonance line of atomic vapors and so may also be designated an atomic resonance filter (ARF). This paper will bring out the role of atomic line filters in the filtering of electromagnetic radiation in three context, absorption-re-emission (ALFs), faraday filters and voigt filters with their principles. Also in this paper we will look at how atomic line filters are most often used in LIDAR and other exercises in laser tracking and communication. With the superior filtering system of an ALF, a non-intensified CCD may be used with a continuous wave laser more efficiently. Atomic line filters with pass-bands of about 0.001 nm have been developed to improve the background rejection of conventionally filtered laser receivers.
