Synthesis, DFT calculations and optical nonlinear properties of two derived Schiff base compounds from ethyl-4-amino benzoate

Two Schiff base compounds viz., Ethyl (E)-4-((3-ethoxy-2-hydroxybenzylidene)amino)benzoate(EHB) and Ethyl (E)-4-(((2-hydroxynaphthalen-1-yl)methylene)amino)benzoate(ENB) are synthesized by condensation of ethyl-4-amino benzoate with 2-hydroxy-3-ethoxy benzaldehyde and 2-hydroxy-1-naphthaldehyde. The two compounds are studied and identified by FT-IR, UV-visible, Mass, 1H-NMR and 13C-NMR spectroscopies. The nonlinear refractive index (NRI) of the two compounds are determined, for ENB compound via the diffraction ring patterns (DRPs) and the Z-scan and via Z-scan for the EHB compound, using continuous wave (cw) low power laser beam, and founds of the order of 10-7 cm2/W due to the first technique and 10-8 cm2/W due to the second technique. The optical limiting (OLg) property of both compounds is studied too with OLg thresholds of 16.5 mW and 11 mW for the compounds EHB and ENB respectively, which makes these two compounds as candidates to be used as an optical limiter (OLr). The DRPs are numerically simulated based on the theory of Fresnel-Kirchhoff with reasonable agreement compare to the experimental findings.

Design and calculation of photoelectric properties of type-II superlattice photodetectors with diffraction ring structure

The photoelectric properties of type-II superlattices (T2SLs) infrared detectors with diffraction ring resonance structure are calculated and studied in this paper. In order to improve the quantum efficiency (QE), diffraction rings are designed on the top surface of T2SLs detectors to control the incident light inside. The maximum QE of ordinary detector is about 30%, while the detector with square diffraction rings is about 80%, and the detector with circular diffraction rings is about 60%. It shows that the structures with diffraction ring can significantly improve the QE of photodetectors. In addition, the size and shape of the resonator are studied. it is obvious that the optimization effect of the square diffraction ring is better than that of the circular diffraction ring, and the square diffraction ring is insensitive to the size change, so it is suitable for the manufacture of practical photodetectors. At the same time, the dark current mechanism of the detector is analyzed and the corresponding specific detectivity is calculated.

Standardization of Cosα Method for X-Ray Stress Measurement

Performing X-ray stress measurement by a new method called the cosα method is spreading in Japan. The cosα method is characterized in that the entire diffraction ring is used and analysed. As a result, the measurement speed is fast, and the device can be downsized. On the other hand, the conventional sin2ψ method requires precise measurement of diffracted X-rays at several X-ray incident angles, which increases the measurement time and the size of the device. In addition, since only a small part of the diffraction ring generated during the X-ray irradiation is used, some of the information on the diffraction ring cannot be used so it is a wasteful method. In 2012, cosα method equipment was released in Japan. Since then, cosα method X-ray stress measurements have been performed at more than 300 facilities. In response to this situation, the Japan Society for Nondestructive Inspection (JSNDI) together with public and private institutions established a study group on the cosα method in 2014, and examined the cosα method and its appropriate use. In this paper, we report the results of this study group.

Preparation, characterization, and study of the nonlinear optical properties of a new prepared nanoparticles copolymer

The nonlinear optical properties of a nanoparticle polyaniline/polyacrylonitrile (PAn/PANr) copolymer newly prepared via experimental and theoretical findings are reported. Diffraction ring patterns result in the far field when a CW, visible, 473 nm, low power laser beam traverses the solution of PAn/PANr in the solvent ethanol. The diffraction ring patterns are usually used to estimate the nonlinear refractive index while the Z-scan is used to measure both nonlinear refractive index and its sign and nonlinear absorption coefficient. The experimentally observed ring patterns are numerically reproduced via the use of the Fresnel–Kirchhoff procedure. Good agreement between experimental findings and the numerical ones are obtained. The obtained diffraction ring patterns suffer modification in the vertical direction due to convection current as a result of local heating of the sample and the presence of gravity.

Evaluation of Railway Rails Suffered from Rolling Contact Fatigue Using X-Ray Generalized cosα Method

In this study, the diffraction rings were measured point by point all over the head of rail sample which was used in service, and shearing stresses with respect to the depth direction were determined using the generalized cosα method. The full width at half maximum was also estimated from the diffraction ring.