Thermal Relaxation Spectra for Evaluating Luminescence Quantum Efficiency of CASN:Eu2+ Measured by Balanced-Detection Sagnac-Interferometer Photothermal Deflection Spectroscopy

Abstract

Highly sensitive broadband photothermal spectroscopy with a white-light lamp as the excitation source was developed by combining a Sagnac interferometer and balanced detection with a photothermal deflection method. A probe beam was split by a birefringent crystal CaCO3 into signal and reference beams with a balanced intensity. This balanced detection enabled the measurement of photoexcited thermal relaxation spectra of materials in the air over the whole visible range in the weak excitation limit 50 µW/cm2. The photothermal excitation spectrum of Eu2+-doped CaAlSiN3 phosphors (CASN:Eu2+) with a high luminescent quantum efficiency was measured to be distinctly different from the photoluminescence excitation spectrum which reflects the absorption spectrum, revealing the thermal relaxation mechanism of the phosphor. Assuming a typical non-radiative relaxation from the higher excited states to the lowest excited state and successively to the ground state, it is demonstrated that the photoluminescence efficiency of the phosphors is readily evaluated simply by comparing the photothermal and photoluminescence excitation spectra.

Enhancing luminous flux and color rendering of laser-excited YAG:Ce3+ single crystal phosphor plate via surface roughening and low-temperature sintering a CaAlSiN3:Eu2+ phosphor-in-borate glass

“…For SCP-PiBG, the measured CRIs in both I-model and E-model were 70 and 76, respectively. However, the CASN: Eu 2+ PiBG layer decreased the luminous efficacy as the low conversion efficacy of CASN: Eu 2+ phosphor and the low spectral luminous efficacy of red light emission [35,36]. Compared with SCP sample with R a = 0.035 μm, the luminous flux and CRI of SCP-PiBG-I sample increased by 31.48% and 117.14%, respectively.…”

Diffracted Beams from Metasurfaces: High Chiral Detectivity by Photothermal Deflection Technique

“…[28] it was applied in photothermal threshold quantum yield measurements of CdSe/CdS quantum dots, while in ref. [29] it was combined with a Sagnac interferometer to study the photothermal excitation spectrum of a highly luminescent phosphor. Finally, although PDT was applied to study plasmon-enhanced Si thin films for solar cell applications, [30] it has never been applied to study plasmonic metasurfaces and their chiral properties.…”

Characterization of Chirality in Diffractive Metasurfaces by Photothermal Deflection Technique

“…PDT is usually used for scattering-free and non-destructive characterization of different solid materials [27][28][29][30]. It was not until recently that scientist realized the new possibilities of using PDT to study thermal effects at the nanoscale, e.g., for plasmonenhanced solar cells [31], photon quantum yield in quantum dots [32], and phosphor with high photoluminescence efficiency [33]. We recently proposed a PDT setup as a cheaper and simpler alternative to diffraction spectroscopy: we measured chirality-dependent diffraction orders in asymmetric metasurfaces [34].…”