Broadband anti-Stokes white emission of Sr₂CeO₄ nanocrystals induced by laser irradiation

Abstract

The laser induced white emission (LIWE) from SrCeO nanocrystals upon irradiation with a focused IR laser beam was investigated. It was observed to be a threshold phenomenon with its intensity increasing exponentially with the excitation power density. This process was investigated under double laser beam simultaneous excitation in the UV range leading to Stokes emission in the visible range and in the IR range leading to anti-Stokes LIWE. With increasing LIWE intensity, the Stokes emission intensity strongly decreased. The LIWE is accompanied by efficient photocurrent generation depending on laser excitation density followed by multiphoton absorption and ionization processes. Photoimpedance measurements showed a sharp increase of the dielectric constant by several orders of magnitude in the SrCeO nanocrystals during the LIWE process demonstrating a metallic-like behaviour. The mechanisms of LIWE include multiphoton absorption and ionization that lead to the creation of a coupled pair of Ce and Ce ions that allow for the intervalence charge transfer (IVCT) emission transitions in the white light range. A strong decrease of absorption band intensity of SrCeO with increasing LIWE intensity confirms the creation of (Ce, Ce) pairs.

Laser induced white lighting of graphene foam

“…This emission was characterized by relatively low temperature of the emitting sample, threshold behavior of the intensity increasing exponentially with the excitation power and high energy efficiency. Since then, the white emission has been observed in rare earth doped nanocrystalline powders, ceramic, glasses and bulk crystals, as investigated by several groups1011121314151617181920. The bright white emission was also reported for undoped nanocrystalline powders by the Di Bartollo group212223.…”

Understanding Near Infrared Laser Driven Continuum White Light Emission by Graphene and Its Mixture with an Oxide Phosphor

“…Especially, white light emission from single/few‐layered graphene as well as graphene powders shows similar white light spectra under both ultrafast pulse or CW NIR laser excitation, which has been generally understood by a thermal emission mechanism . In comparison, nonthermal processes have been often considered to account for the while light generation in inorganic phosphors as well as metalorganic compounds . Despite that the suggested mechanisms differ from material to material, these observations imply that this continuum white light generation is not limited to RE/TM doped phosphors, but rather a general process as long as the NIR laser can be efficiently absorbed by the materials.…”

Study of structural, electrical, and photoluminescent properties of SrCeO3 and Sr2CeO4

“…Tuneable luminescence of Sr 2 CeO 4 :M 2+ (M = Ca, Mg, Ba, Zn) and Sr 2 CeO 4 :Ln 3+ (Ln = Eu, Dy, Tm) nanophosphors have been studied [22]. Recently studies about anti-Stokes white light generated from undoped [24], Nd 3+ [25], and Eu 3+ -doped [26] Sr 2 CeO 4 under near infrared excitation were published. It is reported that emission colour of Eu 3+ doped Sr 2 CeO 4 nanophosphors depends on temperatures which make them useful for nanothermometry technology.…”