Optical gain due to the Eu transition in the alloy of Ca1-xEuxGa2S4 Original Research Article

Room temperature photoluminescence quantum efficiency of the alloy of Ca1−xEuxGa2S4 was measured as a function of x, and was found to be nearly unity under excitation at peak wavelength of excitation spectrum (510 nm) in the x range of 0.01≤x≤0.2. At larger x values, it tends to decrease, but still as high as 30% for stoichiometric compound EuGa2S4. Taking these backgrounds into account, pump-probe experiments were done with Ca1−xEuxGa2S4 for searching optical gain at x=0.2. The optical gain of nearly 30 cm−1 was confirmed to exist, though the pumping induced transient absorption which seems to limit the higher gain was found.