“…It * minami@bk.tsukuba.ac.jp † Present address: Institute for Solid State Physics, University of Tokyo, Kashiwa, Chiba 277-8581, Japan; ksato1014@icloud.com ‡ Present address: Wide Bandgap Materials Group, Optical and Electronic Materials Unit, Environment and Energy Materials Division, National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan; YAMAMOTO.Takashi@nims.go.jp involves covering the sample with a thin polymer film containing rare-earth complexes, exciting the complexes with ultraviolet (UV) light, and measuring their resulting T -dependent photoluminescence (PL). By applying this technique to thin films of YBCO and the high-T c superconductor Bi 2 Sr 2 CaCu 2 O 8+δ (Bi2212), the photoluminescence of the covering polymer film provided detailed maps of the hot spot T (r) in the superconducting film without any scanning distortions, because this technique allows for a direct measurement of T (r) [9][10][11][12]. However, even such measurements can include T (r) distortions caused by multiple light reflections from parallel regions of the polymer film surface and variable fluorescence efficiencies arising from regions of nonuniform polymer film thickness, especially at the sample's corners and edges [9].…”