Site-selective occupancy of Cr3+ enabling tunable emission from near infrared I to II in fluoride LiInF4:Cr3+

A new broadband NIR II emission fluoride LiInF 4 :Cr 3+ peaking at 1000 nm with a FWHM of 220 nm is demonstrated using a site-occupancy control strategy. The NIR II emission is originated from the Cr 3+ at seven coordinated crystal field environments.