Tailored Magnetic Linear Birefringence in Wedge-Shaped Co Nanocluster Assemblies

The purpose of this paper is to present an experimental method to induce strong magnetic linear birefringence in two-dimensional assemblies of Co nanoclusters grown on glass plates. Additionally, we have also correlated the magnitude and characteristics of that nonlinear magneto-optical effect with the thickness and profile of those disordered nanostructures. For those aims, we have grown Co nanocluster assemblies on amorphous substrates, by means of pulsed laser ablation in off-axis geometry. This approach enabled us to obtain magnetic media with an intended and pronounced thickness profile, i.e., wedge-shaped assembly, to investigate the orientation and behavior of surface magnetization regarding both the thickness gradient direction and in-plane magnetic field. That study was accomplished by measuring the magneto-optical effects in reflection and transmission configurations, unveiling an out-of-plane magnetization whose magnitude depends closely on the thickness gradient direction. That component, arising from a graded magnetic anisotropy along the wedged nanostructure, adds a reversal mechanism to the surface magnetization, thus being responsible for the magnetic linear birefringence in our ultrathin Co assemblies.

Temporal dynamics of change of polycrystalline component of bioctisses and blood of death from poisoning by alcohol and carbon with different time since death

The article contains the results of a study of the effectiveness of forensic medical determination of the prescription of death by the method of differential Müller-matrix polarization-phase tomography, which is implemented by multichannel probing of rhizopolarization with laser beams of histological sections of the brain, myocardium, adrenal glands, liver and blood of the deceased and multichannel polarization filtration series images with algorithmic reproduction (reconstruction) of coordinate distributions (tomograms) of the average linear birefringence (LD) of polycrystalline networks. Aim of the work. Efficiency study by the method of differential Müller-matrix polarization-phase tomography for determining the duration of death. Materials and methods. The object of the study was the histology of samples of human internal organs (brain, myocardium, adrenal glands, and liver) with different duration of damage from 6 hours to 48 hours (we used BT samples from those who died from alcohol poisoning and carbon monoxide poisoning). For control, we used BT samples from those who died from ischemic heart disease with different duration of damage from 6 hours to 48 hours. The studies were carried out using the method of differential Muller-matrix polarization-phase tomography. Results. The range of linear change in the magnitude of the higher-order statistical moments, and accordingly the analytical determination of the DNS, lies in the range from 20 hours to 48 hours. The accuracy of determining the DNS is also significantly improved and amounts to 0.5 hours. Conclusion. The high efficiency of Muller matrix algorithmic reproduction of maps of average values of birefringence of the optically anisotropic component of biological preparations of the deceased was revealed.

Investigation of polar crystalline materials containing hydrochlorothiazide: electron density distribution and optical properties

The polar hydrochlorothiazide polymorph (I) (systematic name: 6-chloro-1,1-dioxo-3,4-dihydro-2H-1,2,4-benzothiadiazine-7-sulfonamide, C7H8ClN3O4S2) and, recently designed by us, the polar 2-aminopyridine hydrochlorothiazide water <1/1/1> (C7H8ClN3O4S2·C5H6N2·H2O), (II), have been investigated. The crystal structures of both materials were determined using the single-crystal X-ray diffraction technique. The intermolecular interactions in (I) and (II) were studied in detail via topological electron-density analysis. The obtained results showed hydrogen bonds with a character intermediate between closed-shell and shared-shell in both crystal structures. The most important hydrogen bonds in (I) are formed between sulfonamide groups, whereas in (II), water molecules play a crucial role as they interconnect 2-aminopyridine and hydrochlorothiazide molecules. Calculations of the optical properties revealed that both materials exhibit large linear birefringence, twice that of calcite. The theoretically predicted second harmonic generation efficiency is four times and five times larger than that of KH2PO4 for (I) and (II), respectively. The information gathered on intermolecular interactions and structure–property correlations was used to identify the best strategies for the future design of new functional materials of this kind.

Forensic differential diagnosis of ethanol and carbon monoxide poisoning by diffused tomography of polarization images of polycrystalline blood films

This work is devoted to the study of the possibilities of applying the method of differential polarimetric microscopy with algorithmic reproduction of fluctuations of linear and circular birefringence of polycrystalline component of human blood films in forensic practice for differential diagnosis of alcohol and carbon monoxide poisoning. Aim of the work. Development of a set of forensic objective criteria for the possibility of differential diagnosis of ethanol and CO poisoning by diffuse tomography of polarization images of polycrystalline films of human blood. Materials and methods. The object of the study were polycrystalline blood films obtained from 98 corpses of both sexes aged 18 to 70 years. The cause of death was acute ethanol poisoning (n=36), acute CO poisoning (n=32) and biological tissue samples from those who died of coronary heart disease (n=30) were used for control. The studies were performed by diffuse tomography of linear and circular birefringence of fluctuations of the polycrystalline structure of human blood films. Results. The results of statistical analysis of data of algorithmic polarization reproduction of coordinate distributions of linear birefringence of fluctuation of albumin-globulin polycrystalline networks and circular birefringence of optically active chiral molecules, revealed a high level (statistical reliability p1; p2; p1;2<0,05) of diagnostic efficiency of forensic digital differentiation of blood films samples from people died of coronary heart disease, ethanol and carbon monoxide poisoning based on the calculation of a set of statistical moments of the 1-4-th orders. Conclusions. The possibility of statistically significant (p1; p2<0,05) differentiation of cases of ethanol and CO poisoning by diffuse tomography of linear and circular birefringence of fluctuations of the polycrystalline component of the blood films has been established. The operational characteristics of the diagnostic power of the method corresponding to the excellent (92 % and 97 %) level are determined.

Spin Laser Local Oscillators for Homodyne Detection in Coherent Optical Communications

We numerically investigate spin-controlled vertical-cavity surface-emitting lasers (spin-VCSELs) for local oscillators, which are based on an injection locking technique used in coherent optical communications. Under the spin polarization modulation of an injection-locked spin-VCSEL, frequency-shifted and phase-correlated optical sidebands are generated with an orthogonal polarization against the injection light, and one of the sidebands is resonantly enhanced due to the linear birefringence in the spin-VCSEL. We determine that the peak strength and peak frequency in the spin polarization modulation sensitivity of the injection-locked spin-VCSEL depend on detuning frequency and injection ratio conditions. As a proof of concept, 25-Gbaud and 16-ary quadrature amplitude modulation optical data signals and a pilot tone are generated, and the pilot tone is used for the injection locking of a spin-VCSEL. An orthogonally-polarized modulation sideband generated from the injection-locked spin-VCSEL is used as a frequency-shifted local oscillator (LO). We verify that the frequency-shifted LO can be used for the homodyne detection of optical data signals with no degradation. Our findings suggest a novel application of spin-VCSELs for coherent optical communications.

CD Imaging at High Spatial Resolution at Diamond B23 Beamline: Evolution and Applications

Circular Dichroism imaging in the 190–650 nm spectral region pionered at Diamond Light Source B23 beamline, has been made possible by the highly collimated microbeam generated at the beamline and has been used to study the homogeneity of the supramolecular structures of thin films of chiral materials deposited on fused quartz substrates. This facility has been expanded with the installation of a Mueller Matrix Polarimeter, MMP, coupled to the beamlight, of which a preliminary data will be discussed. In the solid state, the measurement of CD related to the supramolecular structure is hampered by the presence of circular birefringence, linear dichroism, and linear birefringence that can only be evaluated using the MMP technique. The ability to characterize the chiroptical property of thin chiral films prepared under a variety of conditions and protocols such as drop cast, spin coating, spray at different temperatures and concentrations will enable the determination of the critical parameters for reproducible, uniform and homogeneous specimen preparation, which is the sine qua non for any commercial application. This is of particular importance for optoelectronic materials, but it can also be extended to a broad variety of materials with applications from biosensors to biological tissues.