Ultrahigh sensitivity upconversion low temperature sensorsviamanipulating the non-thermally coupled levels of Er3+ions

The GC material produces excellent blue UC emission under 980 nm or 1550 nm excitation, where the blue emission level ( 2 H 9/2 ) could form a novel NTCL ( 2 H 11/2 – 2 H 9/2 ) with other energy levels, realizing ultrahigh sensitivity low temperature sensing.