Near-infrared (NIR) to red and green up-conversion emission from silica sol-gel thin films made with La0.45Yb0.50Er0.05F3 nanoparticles, hetero-looping-enhanced energy transfer (Hetero-LEET):: A new up-conversion process

Bright green and red luminescence has been generated with a 980 nm diode laser from silica sol-gel thin films made with La0.45Yb0.50Er0.05F3 nanoparticles through a newly described hetero-looping-enhanced energy-transfer (hetero-LEET) up-conversion process, which exhibits a power dependence similar to that of a photon avalanche (PA). The hetero-LEET mechanism is potentially more efficient than PA, ground-state absorption/excited-state absorption (GSA/ESA), and energy-transfer (ETU) mechanisms because it combines resonant ground-state absorption with a looping or feedback process.