Illustration from Scientific Research

c) ESA@1060 nm and energy looping through cross-relaxation (CR) processes lead to 800 nmphoton-avalanching phenomenon, i.e., very steep relationship between luminescence intensityILat 800 nm (inset) under 1060 nm photoexcitation pump intensityIPabove the pump threshold (ITH). d) The pump-power-dependent energy looping leads to slow population buildup time of the looping (n2) and emitting (n3) levels (pulse width Δ = 200 ms), these two levels show slow luminescence decays under pulsed excitation. e) The oddment population of level 2 is responsible for significant paired-pulsed facilitation (PPF) index (pulse width Δ = 0.2 ms, time gapδ= 2 ms) as compared to individual, displaced pulses (δ= 20 ms); data in (d,e) were simulated forIP= 10 kW cm−2. The colors in (b–e) correspond to each other.

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