Journal of Nonlinear Optical Physics & Materials

The development of crystal growth and measurement methods opens new possibilities for studying materials with remarkable nonlinear optical features. The development of bulk crystals is a constant concern to be beneficial for device applications. This study focuses on the development of nonlinear optical crystals of L-histidine complexes, characterization approaches, and prospective applications. The solution growth approach, a straightforward, inexpensive, and low-temperature growth technique, was adopted broadly. Recent studies show that L-histidine derivatives have potential optical, SHG, thermal, dielectric, and mechanical properties, making them an excellent choice for nonlinear optical devices. In this work, structural, spectroscopic, chemical composition, linear and nonlinear optical analyses, thermal, and dielectric characterizations of L-histidine derivatives were conducted. Most of the L-histidine complexes were found to be crystallized in orthorhombic and monoclinic crystal systems with P2₁2₁2₁ and P2₁ space groups. The crystalline perfections of the samples were analyzed by the HR-XRD method. The energy-dispersive X-ray (EDX) spectroscopic technique was applied to evaluate the chemical content of the compounds. FT-IR and FT-Raman techniques were used to recognize the molecular vibrations and functional groups of the L-histidine derivatives. The UV-visible and photoconductivity studies were done to examine the optical behaviors of the developed crystals. Most of the crystals were found to have excellent optical transparency and wide bandgaps. It has been observed that L-histidine hydro-fluoride dehydrate and L-histidine tetrafluoroborate are found to have the highest second harmonic generation (SHG) efficiencies. The dielectric analyses were utilized to study the dielectric constant and dielectric loss variations with the applied frequency. According to the thermal analyses, most of the crystals were found to have substantial thermal stabilities suitable for device applications.

In this paper, we have studied the process of monochromatic pump light in linearly chirped Periodically Poled ${\text{KTiOPO}}_4$ (PPKTP) nonlinear crystal to generate single-cycle biphotons under Quasi-Phase-Matching (QPM) conditions through a Spontaneous Parametric Down-Conversion (SPDC). A detailed analysis of the phase mismatching function reveals that in PPKTP crystals, for the proper frequency range, the phase mismatching $\mathrm{\Delta }k$ is stable and relatively close to 0 due to the relatively stable refractive index, and therefore has a good phase matching effect. Even when the chirp rate becomes small, it is able to produce single-cycle biphotons due to the near-perfect phase matching. Of course, as the chirp rate increases, the frequency response range becomes wider, the temporal width is narrower, and the number of cycles is smaller.

By using the slow evaporation solution growth technique, the 2-amino 6-methyl pyridinium 4-methyl benzoate (2A6MP4MB) is crystallized in a single, high-quality crystal. Single crystal X-ray diffraction (SXRD) was used to determine the crystal structure. The different functional groups of the substances were identified using Fourier Transform Infrared Spectroscopy (FTIR) analysis. The 2A6MP4MB crystal exhibits a significant optical transmittance throughout the complete visible spectrum and a lowered UV cutoff wavelength, according to studies conducted using UV-Vis spectrometers. The optical band gap energy (Eg) of a single crystal of 2A6MP4MB is 4.768eV. The compound’s photoluminescence (PL) spectrum in the title illustrates the green emission technique. We analyze the produced single crystal’s dielectric tensorial behavior at various frequencies. The produced 2A6MP4MB crystal’s third-order susceptibility, nonlinear refraction, and nonlinear absorption coefficient were evaluated using the $Z$-scan technique. A Vickers hardness tester was used to assess the created crystal’s mechanical stability.

A theoretical model for determine the optimal focusing parameter for second harmonic generation (SHG) process in a polycrystalline nonlinear medium has been constructed. Theoretical calculations were confirmed by an experiment to obtain SHG at a wavelength of 968nm in a zinc selenide polycrystal using a thulium laser.

This work investigates the polarization modes i.e., Extraordinary (E-mode) and Ordinary (O-mode) on self-focusing of higher-order mode of elegant Hermite-cosh-Gaussian (EHChG) laser beams within collisionless magnetized plasma medium. In this study, the authors have taken transverse electromagnetic (TEM) mode with mode indices (0, 4) and explored. The ponderomotive force is primarily responsible for the dielectric constant’s nonlinearity in this context. Also, WKB and paraxial approximations via the parabolic wave equation approach are used to establish the general form of differential equations for beam-width parameters in both transverse dimensions of the beam. In this paper, the authors have theoretically investigated the dominance of polarization modes and absorption coefficient on self-focusing. The final results show good enhancement of laser propagation through collisionless plasma medium.

The primary aim of this investigation is to uncover novel optical soliton solutions (OSSs) and conduct a comprehensive stability analysis of a particular model. The extraction of OSSs is facilitated through two potent techniques: the advanced auxiliary equation and the $(w/g)$-expansion approaches, both proven to be highly effective in revealing soliton solutions in various nonlinear evolution equations. In this paper, we provide an in-depth exposition of the obtained solutions, elucidating them both graphically and in their physical context. Furthermore, we investigate the influence of diverse parameters on these results by presenting several graphical representations. Additionally, we delve into the stability of equilibria and conduct a thorough phase-plane analysis of the model. To provide a broader context, we also offer a comparative discussion of our solutions in relation to previous works in the field. Considering the significance of the stochastic chiral nonlinear Schrödinger equation in soliton theory, the solutions obtained here hold the potential to illustrate intricate physical phenomena and find applications across diverse fields in the realm of communication systems.

In this paper, the general theory of generating fast light and slow light in erbium-doped fiber by hybrid pump cascade structure based on coherent population oscillation effect is given. Through numerical simulation, the effects of pump optical power ratio ($M$) on gain, group-induced refractive index $n_g$, time delay and fractional delay of pumping structure (1480 and 980nm) and pumping structure (980 and 1480nm) are studied and analyzed. The effects of pumping structure and pumping direction on time delay, fractional delay and fast/slow light conversion are discussed. In addition, the effects of different pump optical power ratios ($M$) on time delay and fractional delay are also discussed. Compared with previous methods such as changing the interaction length and doping ion density, a more suitable optical transmission speed can be obtained by adjusting pump composition, pump direction and pump ratio ($M$). This may lead to the optimization of optical communication systems.

Within the density functional theory, the Hartree–Fock/Kohn–Sham-coupled perturbation method using the basis of localized orbitals, the gradient PBE functional with dispersion correction D3(BJ) and hybrid PBE0 and B3LYP functionals, the structural, dielectric, and piezoelectric properties of hexagonal alkali fluorocarbonates ABCO₃F (A: K, Rb, Cs; B: alkaline earth (Mg, Ca, Sr) and $d^{10}$ (Zn, Cd, Pb)) were evaluated. In the series of crystals, fluorocarbonates with lead have the highest values of the calculated components of the dielectric constant tensor, piezoelectric constants, and nonlinear optical (NLO) coefficients.