The harmonic generation effect, a distinct nonlinear optical phenomenon , exhibits unique properties and has critical applications across multiple fields. However, harmonic generation during optical measurements can introduce significant interference or experimental errors. Here, we investigated the photoluminescence (PL) characteristics of Dy 3+ doped CaWO 4 phosphors under near-infrared (NIR) irradiation. Both characteristic yellow and blue emissions of Dy 3+ and a series of NIR-induced harmonic generation were observed. The study demonstrated that Dy 3+ emissions were excited by harmonic generation originating from the dual-grating configuration of a spectrophotometer. Leveraging the divergent temperature-dependent intensity evolution between Dy 3+ emissions and 1.5th harmonic generation, we proposed a novel ratiometric thermometric strategy based on the luminescence intensity ratio (LIR). This new thermometry achieved optimal temperature sensitivity, with a maximum absolute sensitivity of 74.57 × 10 −4 K −1 and relative sensitivity of 2.21 % K −1 , surpassing conventional ratiometric thermometry relying on thermally coupled energy levels. These findings not only clarified the origin of multiplex harmonic generation and its impact on spectral measurement but also harness harmonic generation for innovative applications in optical thermometry.
Element substitution of BaTiO 3 -based compounds has been demonstrated as a powerful way for designing novel electronic materials (such as polar metals and multiferroics). To trigger magnetism into ferroelectric BaTiO 3 , general substituted elements are magnetic transition metals (such as Mn, Fe, and Co). The doping effect of rare-earth elements (such as Dy) in BaTiO 3 -based compounds was barely investigated. Here, we report the coexistence of magnetism and electric polarization in epitaxial Dy 0.5 Ba 0.5 TiO 3 films. The single-crystalline films were synthesized by high-pressure magnetron sputtering. The crystal and electronic structures were characterized by high-resolution x-ray diffraction, x-ray photoemission spectroscopy, and resonant soft x-ray absorption spectroscopy. Room-temperature electric polarization was demonstrated by optical second-harmonic generation. Temperature-dependent magnetic hysteresis loops were measured to reveal the revolution of magnetism on temperature. Surprisingly, it is uncovered that the Curie temperature of electric-polarized Dy 0.5 Ba 0.5 TiO 3 films is around 100 K, far above the critical temperature of non-polarized DyTiO 3 (near 60 K). Our work provides another view to understand the magnetoelectric materials.
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