Sensitivity of cw and pulsed laser-pumped Pr infrared quantum counters

Abstract
The characteristics of LaBr3 : Pr and LaCl3 : Pr infrared quantum counters used for detection near 4.5 μm have been investigated in detail. Quantum efficiency for infrared‐to‐visible upconversion is in agreement with our estimates based on the spectroscopic properties of these materials. Highest sensitivity was obtained with pulse laser pumping in LaCl3 : Pr at 82 °K. Maximum crystal quantum efficiency and detectivity under these conditions were Q=1.2×10−3 and D*=1.4×109 cm Hz1/2/W. The detectivity is the highest reported for any IRQC device. Pump‐induced fluorescence measured without ir signal proved to be the limiting source of noise for both cw and pulsed pumping.