The photon avalanche: A new phenomenon in Pr3+-based infrared quantum counters

Studies of laser-pumped Pr3+ infrared quantum counters have led to the discovery of a new photon avalanche region, occurring when pump flux exceeds a certain critical value. Infrared output near 4.5 μm is associated with the large visible output, and pump power is strongly absorbed. Critical pump power density is in the range 1.2–12.2 W/cm2.