This is an interesting subject. Lead Sulphide, according to: http://antonirogalski.com/wp-content/uploads/2012/12/History-of-infrared-detectors.pdf http://anto

This is an interesting subject. Lead Sulphide, according to: http://antonirogalski.com/wp-content/uploads/2012/12/History-of-infrared-detectors.pdf http://antonirogalski.com/wp-content/uploads/2012/12/History...