Nonlinear Diffuse fs-Pulse Reflectometry of Harmonic Upconversion Nanoparticles

Abstract

Nonlinear diffuse femtosecond-pulse reflectometry is introduced as a powerful experimental tool for the unambiguous characterization of polar and non-polar point symmetry groups of harmonic upconversion nanoparticles. Using intense ultrashort 40 femtosecond laser pulses and an appropriate figure of merit (FOM), second and third harmonic emission serve for the structural characterization of polar Yb-doped lithium niobate and non-polar titanium dioxide nanoparticles. The tool is capable of differentiating these two samples by FOM values that differ by up to 13 orders of magnitude. The general applicability to harmonic upconversion nanoparticles over a broad range of intensities and wavelength spectrum, is discussed.

Absorption and Remission Characterization of Pure, Dielectric (Nano-)Powders Using Diffuse Reflectance Spectroscopy: An End-To-End Instruction

“…DR) against the photon energy hν, the band gap energy E g can be extracted by a linear fit at its rise as shown in Figure 12. The crossing point between fit and abscissa will then immediately yield E g [41,[111][112][113]. This procedure is also known as Tauc plot and is a powerful tool in the field of quantitative determination of band gaps and absorption centers.…”

“…An alternative method captivates by a comparably simple setup and easy preparation routine [41]. Especially for a low amount of samples to be reproducibly prepared, this may be a valid choice to the before-presented powder press.…”

Combining photoinduced linkage isomerism and nonlinear optical properties in ruthenium nitrosyl complexes

“…Single crystals of trans-[RuNO(NH 3 ) 4 F]SiF 6 were ground in a mortar and pressed into a powder pellet as described by Kijatkin et al (2017). For comparison, the same procedure was performed using magnesium-doped lithium niobate (LiNbO 3 :Mg) nanoparticles (mean particle size d ' 90 nm).…”

“…Simultaneously, the TH signal of trans-[RuNO(NH 3 ) 4 F]SiF 6 is up to an order of magnitude weaker than for LN, which can be explained by an absorption band in the range of 400-550 nm. As a result, the harmonic ratio f R , describing the polarity of the material and providing an accessible quantity for the characterization of second-order nonlinearities (Kijatkin et al, 2017;Athmani et al, 2019), is considerably higher for the ruthenium complex compared with LN.…”

“…Third-harmonic (TH) generation, by contrast, is present in any space group and medium. Therefore, the ratio of the emission intensities of SH and TH can be exploited to gauge the NLO properties of new materials with respect to a standard (Kijatkin et al, 2017). Furthermore, a strong molecular dipole moment enhances the polarization effect and leads to even higher SH and TH intensities.…”