Nonlinear Photo‐Thermal Incandescence‐Like Emission in Ln₂Hf₂O₇ (Ln = Er³⁺, Nd³⁺, Sm³⁺) Phosphors

Abstract Ultrabroadband continuous emission spanning the visible to infrared spectrum can be generated through continuous laser irradiation of optically active materials, which is of great significance for precision spectroscopy, sensors, and detection applications. In this study, the generation of incandescence‐like continuous white light emission (CWL) is reported from rare‐earth (RE) hafnates Ln₂Hf₂O₇ (Ln = Er³⁺, Nd³⁺, Sm³⁺) under continuous wave laser excitation. With the increase in excitation power density, the emission spectra evolve from characteristic narrow‐band upconversion (UC) emission to the continuous broadband spectra in different RE hafnates. The dependence of emission intensity on excitation power exhibits a distinct threshold, beyond which the brightness increases sharply. Using an infrared thermal camera, it is observed that the rise in emission intensity above this threshold is accompanied by a rapid increase in sample temperature induced by laser irradiation. This thermal origin of the CWL emission contributes to a clear nonlinear dependence on sample temperature, while the difference in the CWL intensity for the examined RE hafnates can be rationalized by considering their difference in high temperature spectral emissivity. This method for producing strong and broadband CWL emission can facilitate the development of efficient continuum broadband light sources for emerging applications from imaging to spectroscopy.