The complex trans‐[RuNO(NH3)4F]SiF6 was synthesized in quantitative yield and the structure was characterized by X‐ray diffraction and spectroscopic methods. The complex crystallizes in the non‐centrosymmetric space group Pn. Hirshfeld surface analysis revealed that the dominant intermolecular interactions are of types H…F and F…O, which are likely to be responsible for the packing of the molecules in a non‐centrosymmetric structure. Irradiation with blue light leads to the formation of Ru–ON (metastable state MS1) and Ru–η2‐(NO) (metastable state MS2) bond isomers, as shown by IR and UV–Vis spectroscopy. The structural features of the MS1 isomer were elucidated by photocrystallography. The complex exhibits exceptionally good thermal stability of the metastable state MS1, such that it can be populated by light at 290–300 K, which is important for potential applications. The second harmonic (SH) emission can be generated by femtosecond‐pulsed irradiation of the complex. The generated SH is rather efficient and stable under long‐term exposure. Finally, since both metastable states and harmonic generation can be generated at room temperature, an attempt to drive the SH response by photoisomerization of the nitrosyl ligand was made and is discussed.

This paper addresses the challenging task of optical characterization of pure, dielectric (nano-)powders with the aim to provide an end-to-end instruction from appropriate sample preparation up to the determination of material remission and absorption spectra. We succeeded in establishing an innovative preparation procedure to reproducibly obtain powder pellet samples with an ideal Lambertian scattering behavior. As a result, a procedure based on diffuse reflectance spectroscopy was developed that allows for (i) performing reproducible and artifact-free, high-quality measurements as well as (ii) a thorough optical analysis using Monte Carlo and Mie scattering simulations yielding the absorption spectrum in the visible spectral range. The procedure is valid for the particular case of powders that can be compressed into thick, non-translucent pellets and neither requires embedding of the dielectric (nano-)powders within an appropriate host matrix for measurements nor the use of integrating spheres. The reduced spectroscopic procedure minimizes the large number of sources for errors, enables an in-depth understanding of non-avoidable artifacts and is of particular advantage in the field of material sciences, i.e., for getting first insights to the optical features of a newly synthesized, pure dielectric powder, but also as an inline inspection tool for massively parallelised material characterization.

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.

In vivo tracking of harmonic nanoparticles (HNPs) in living animals is a technique not yet exploited, despite the great potential offered by these markers, due to a lack of an appropriate tool. The main drawback is the necessity to excite nonlinear effects in the millimeter area in a widefield mode with a sufficient signal to noise ratio. Our approach to this problem consists in a redesign of the laser space parameters in a region of high energy per pulse and low repetition rate in the kHz regime, in counter-trend with the actual microscope research technology. We realise this by means of a regeneratively amplified fs-laser system, creating an easy alignable and reproducible Tunable hIGh EneRgy (TIGER) widefield microscope. This one is successfully applied for HNPs tracking in the blood flow of the heart system of a Drosophila larvae, a powerful platform to study socially relevant diseases, such as congenital heart defects in human beings. It is possible to follow nonlinear emitting marker in a remarkable field-of-view of up to 1.5 × 1.5 mm2 at 70 frame per seconds. The impact of the energy per pulse, the pulse repetition rate as well as of the photon energy on the SNR is determined and the optimum setup conditions are deduced. At the same time, wavelengths of fundamental and harmonic pulses are carefully considered and tailored to match the transmission fingerprint of the Drosophila larvae. Our findings clearly demonstrate the large impact of precise pulse parameter management in the view of the optical features of the sample, the optical setup and the photosensitivity of the detector. A step-by-step instruction for more general use of the technique is described, opening the path for addressing biological research questions that require far-field imaging at high frame rates with exceedingly high spatial and temporal precision.

The structural and nonlinear optical properties of a new anilinium hybrid crystal of chemical formula (C6H7NCl+·NO3−)3 have been investigated. The crystal structure was determined from single‐crystal X‐ray diffraction measurements performed at a temperature of 100 K which show that the compound crystallizes in a noncentrosymmetric space group (Pna21). The structural analysis was coupled with Hirshfeld surface analysis to evaluate the contribution of the different intermolecular interactions to the formation of supramolecular assemblies in the solid state that exhibit nonlinear optical features. This analysis reveals that the studied compound is characterized by a three‐dimensional network of hydrogen bonds and the main contributions are provided by the O…H, C…H, H…H and Cl…H interactions, which alone represent ∼85% of the total contributions to the Hirshfeld surfaces. It is noteworthy that the halogen…H contributions are quite comparable with those of the H…H contacts. The nonlinear optical properties were investigated by nonlinear diffuse femtosecond‐pulse reflectometry and the obtained results were compared with those of the reference material LiNbO3. The hybrid crystals exhibit notable second (SHG) and third (THG) harmonic generation which confirms its polarity is generated by the different intermolecular interactions. These measurements also highlight that the THG signal of the new anilinium compound normalized to its SHG counterpart is more pronounced than for LiNbO3.

Nanocrystals of alkaline niobates are currently being discussed for various applications because of their diverse and remarkable properties. Although the growth of bulk niobate crystals is well established, little is known about respective nanocrystals and the optical properties of niobates below 100 nm. A systematic view of the hydrothermal synthesis of potassium niobate with respect to the precursor species reveals the sensitive dependence of the resulting crystalline phases and sizes on the educt modifications. With a variation of stoichiometry of the procedure, the product modification and crystallite size can be changed. By means of second harmonic generation, nanocrystalline potassium niobate offers the possibility for use as an optical marker in high resolution nonlinear microscopy. Redispersed particles show a significant second harmonic generation signal throughout the visible spectral range.

The usability of the alkali niobates with their ferroelectric and photorefractive properties could be expanded if the development of synthesis methods would allow to obtain small, preferably monodispersed, crystals in...

Thin micropatterned lithium niobate (LiNbO3) layers may be used for photonic components, actuators, and data storage devices because LiNbO3 exhibits nonlinear optical properties as well as anisotropic polarizability and ferroelectric behavior. Commonly, thin micropatterned LiNbO3 layers are integrated into device architectures by complex manufacturing algorithms including direct wafer bonding, mechanochemical wafer thinning or mechanical cleavage of thin LiNbO3 layers from bulk LiNbO3 crystals, as well as lithographic pattering of and/or pattern transfer into the thin LiNbO3 layers. The high‐throughput generation of thin microstructured LiNbO3 layers by parallel additive capillary stamping of environmentally friendly aqueous LiNbO3 precursor solutions with topographically patterned porous polymer stamps is reported. The precursor solutions contain the cheap, commercially available compounds lithium acetate and niobium oxalate hydrate, which are simply dissolved in water as received. In this way, rough surfaces not suitable for layer transfer methods involving direct wafer bonding, such as the surfaces of indium tin oxide (ITO) substrates, are functionalized with microstructured LiNbO3 layers. Microstructured holey 100 nm‐thick LiNbO3 films showing uniform second‐harmonic generation (SHG) except at the positions of the holes are obtained. Orthogonal substrate formation is demonstrated by electrodeposition of gold into the holes, which increases the SHG output 5.4 times.