Search

Solar cells are unable to absorb photons with energies lower than the constituent material's band-gap, which eliminates a significant part of the spectrum. The efficiency of the process may be increased by converting low-energy photon pairs, via nonlinear optical effects, into photons optimal for the solar cell. The converter structures consist of GaN/AlGaN super lattice series perturbed by asymmetric quantum wells which form the Bragg confined structures (BSCs). BCSs support additional bound electron states in the super lattice minigaps, including states above the barrier. Parameters of the structure are optimized for each photon pair, by using the genetic algorithm, to obtain a continual converter.

The nonlinear optical (NLO) performance of rhenium containing azo-based iminopyridine complexes is studied. For this scope, the proven methods of Maker fringe and Z-scan are used. The second and third harmonic generation (SHG and THG) measurements in produced guest-host polymeric films are performed and the corresponding high order susceptibilities are obtained. The Z-scan measurements in solutions are employed for the investigation of nonlinear refraction and nonlinear absorption properties of studied complexes. The enhanced NLO parameters of the Re-containing azo-based iminopyridine complexes comparing to their corresponding ligands confirm the positive role of metal complexation. Moreover, the polarity of connected lateral group has a considerable influence on NLO response of entire complex, in particular, on its NLO refraction behavior. This study promotes the better understanding of the structure-property relationship with possible prediction of NLO properties in such complexes as the design of such type of metal-organic systems has an essential impact on their NLO performance. [ABSTRACT FROM AUTHOR]

Vibrational sum frequency generation (VSFG) spectroscopy is a widely used probe of interfaces and, having ideal surface sensitivity and selectivity, is particularly powerful when applied to wet and soft interfaces. Although VSFG spectroscopy can sensitively detect molecular details of interfaces, interpretation of observed spectra has, until recently, been challenging and often ambiguous. The situation has been greatly improved by remarkable advances in computational VSFG analysis on the basis of molecular modeling and molecular dynamics simulation. This article reviews the basic idea of computational VSFG analysis and recent applications to both aqueous and organic interfaces. [ABSTRACT FROM AUTHOR]

The renormalized coupling constants g that enter the equation of state and determine nonlinear susceptibilities of the system have universal values g at the Curie point. We use the pseudo- ε-expansion approach to calculate them together with the ratios R = g / g for the three-dimensional scalar λ ϕ field theory. We derive pseudo- ε-expansions for g , g , R , and R in the five-loop approximation and present numerical estimates for R and R . The higher-order coefficients of the pseudo- ε-expansions for g and R are so small that simple Padé approximants turn out to suffice for very good numerical results. Using them gives R = 1.650, while the recent lattice calculation gave R = 1.649(2). The pseudo- ε-expansions of g and R are less favorable from the numerical standpoint. Nevertheless, Padé-Borel summation of the series for R gives the estimate R = 0.890, differing only slightly from the values R = 0.871 and R = 0.857 extracted from the results of lattice and field theory calculations. [ABSTRACT FROM AUTHOR]

Two difluoroboradiazaindacene (BODIPY) scaffolds with attached dimethylaminostyryl substituents were synthesized. Guest-host polymeric films were produced by incorporating these chromophores into polymethylmethacrylate matrices. The second and third nonlinear optical properties of the resulting polymer composites were studied by means of the Maker fringe technique using a laser generating at 1064 nm with a 30 ps pulse duration. The macroscopic and microscopic nonlinearities were found to be comparatively high and dependent on the number of dimethylaminostyryl substituents attached to BODIPY core. The development of integrated optics makes such nonlinear films of particular interest, since they can be used in the creation of efficient nonlinear devices. [ABSTRACT FROM AUTHOR]

In this work, we report the experimental study of a Q-switched optical fiber laser based on graphene oxide quantum dots (GOQDs) as saturable absorber (SA). GOQDs are fabricated by carbonization and exfoliation electrospun polyacrylonitrile (PAN) fibers. The results of Fourier Transform Infrared Spectroscopy (FTIR) showed bands caused by the CHs and C[bond, double bond]O groups associated with the GOQDs. The Raman spectrum showed the typical G and D bands of GOQDs. The size of the GOQDs, calculated by Transmission Electron Microscopy (TEM) was 6 nm; additionally, by high resolution TEM (HRTEM), an interplanar distance of 0.19 nm corresponding to the (002) direction of the graphene oxide was calculated. The SA was achieved using the photodeposition technique of the GOQDs onto the core of a single-mode optical fiber. The nonlinear characterization (NLC) of the GOQDs was carried out using the P-scan technique with a high-gain erbium-doped fiber amplifier (EDFA) at a wavelength of 1550 nm. The obtained results showed a saturable absorption behavior with a value of β = - 1.178 x 10 - 6 ( m / W ) and a non-linear susceptibility of I m ( χ ( 3 ) ) ≈ - 1.573 x 10 - 7 ( e s u ) . The experimental results of the SA, based on GOQDs as a switching device in a fiber laser, showed a typical behavior of a Q-switched laser by generating a pulsed emission at a wavelength of 1599 nm, a frequency from 2 to 16 kHz, and a maximum average output power of 1.3 mW., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2023 The Authors.)

[Display omitted] • Cr3+ doped La 2 (WO 4) 3 nanoparticles are synthesized by soft chemical method. • The optical limiting properties of La 2 (WO 4) 3 nanostructures using CW laser at 785 nm was reported for the first time. • All sample possess RSA which is caused by two-photon absorption. • The presence of polarizable Cr3+ ions, results enhanced OL behaviour for 0.7 % Cr3+ doped La 2 (WO 4) 3 nanoparticles. In this article, we discuss the nonlinear optical limiting characteristics of pure and Cr3+ doped La 2 (WO 4) 3 nanoparticles using soft chemical method. We studied the third-order nonlinear optical properties of nanoparticle using a continuous-wave (CW) laser system pumped by a diode laser at 785 nm. The results reveal that the materials possess reverse saturable absorption (RSA) and self-defocusing in nature. Due to the presence of near-resonant excitation state, the material exhibits sequential two-photon absorption (excited state induced thermally) process. We observe a higher non-linear absorption coefficient (β) and nonlinear refractive index (n 2) for 0.7 % Cr3+ doped La 2 (WO 4) 3 systems which is higher than that of pure La 2 (WO 4) 3 nanoparticles. The transmittance decreases with increased input fluence for both pure and Cr3+ doped La 2 (WO 4) 3 samples exposing the optical limiting behavior of the prepared sample. The presence of larger concentrations of more polarizable Cr3+ ions, increased density of states, and higher oxygen defects resulted in enhanced OL behaviour for 0.7 % Cr3+ doped La 2 (WO 4) 3 sample. It is found that two photon absorption (β) is increased from 0.41 to 1.16 × 10-3 and third order nonlinear susceptibility (χ(3)) enhances from 3.909 x10-6 to 6.696 × 10-6 esu on Cr doping. The optical limiting threshold of pure and Cr x La 1-x WO 4 nanoparticles was also studied and found to be in the range of 91.2 to 86.2 W/cm2. As a consequence of the obtained results Cr3+ doped La 2 (WO 4) 3 is likely to be an appropriate candidate for CW low-power optical limiting (OL) applications. [ABSTRACT FROM AUTHOR]

A new organic nonlinear optical single crystal, isonicotinamide bis-paminobenzoic acid (INBAB), is grown from methanol solution using a slow evaporation solution technique. INBAB belongs to a monoclinic system with the space group P21/n. Its relative optical transmittance and optical band gap are found to be 58% and 3.4 eV, respectively. INBAB is thermally stable up to 147°C. The laser-induced surface damage threshold for our crystal is equal to 1.2 GW/cm2 for the 1064 nm Nd:YAG laser radiation. The nonlinear refractive index, the absorption coefficient and the third-order nonlinear susceptibility of our crystal are determined using a Z-scan technique. The material demonstrates optical-limiting behaviour up to the input irradiance of around 5.63 mW. [ABSTRACT FROM AUTHOR]