Optical property of Ce3+-doped lutetium lithium fluoride for the short-wavelength device application

Abstract We report on the optical properties of Ce:LLF excited by the 61-nm wavelength emission of the SPring-8 compact self amplification of spontaneous emission source (SCSS) test accelerator, which is a prototype self-amplified stimulated emission (SASE)-type free electron laser (FEL) that emits extreme ultraviolet (EUV) radiation. Ce:LLF fluorescence at 308 nm and 322 nm wavelength was observed using a streak camera. The temporal profile exhibited a 62.1-ns fast decay component and 8.63-ns slow decay component. This double exponential behavior is observed with EUV-FEL excitation and is due to the de-excitation process involving several relaxation steps because of the energetically long distance and intricate band structure between the excitation and emission states. The double exponential nature of fluorescence decay is not observable with low-energy excitation sources; hence, our results show the importance of novel light sources, such as the FEL, for the development and characterization of new materials.