Journal of Nonlinear Optical Physics & Materials

In this work, I present a novel method for measuring the pulse duration of few-cycle pulses using spectral phase interferometry for direct electric-field reconstruction (SPIDER) with high accuracy. These few-cycle pulses were generated due to nonlinear self-phase modulation (SPM) in nonlinear medium (neon gas) using a one meter hollow-fiber. The observed reconstructed pulse intensity autocorrelation function was varied from 5.35fs to almost 13fs. Moreover, the applied method allows for direct controlling of the output pulse duration through variation of the pulse-width of input pulses at different pressure of neon gas. The observed results indicate that the SPM was enhanced for high neon pressure (2.5atm.) and short input pluses (32fs) without chirping. The obtained results may give an opportunity to monitor and control ultrafast transit interaction in femtosecond chemistry.

This paper analyzes a highly efficient broadband second-harmonic generator in the mid infrared region using an isotropic reverse tapered semiconductor slab configuration, using fractional total internal reflection quasi-phase matching technique. A computer aided simulation has been performed using ZnTe as the nonlinear material which provides an extremely high conversion efficiency of 22.94% with a 3dB bandwidth of 200nm. Effect of varying the slab dimensions on the performance parameters has also been analyzed. Finally, the catastrophic effect caused by destructive interference due to nonlinear law of reflection has also been incorporated in the analysis thereby giving more accurate results.

This paper addresses solitons in optical metamaterials. The semi-inverse variational principle (SVP) is utilized to secure bright soliton solutions to the governing model. There are five forms of nonlinearity that are studied in this paper. They are Kerr law, power law, parabolic law, dual-power law and finally the log law nonlinearity. In particular for Kerr law nonlinearity, there are two additional forms of soliton solutions obtained. They are cosh-Gaussian pulses and bright-dark combo solitons and these are collectively being referred to as exotic solitons. There are several constraint conditions that naturally emerge for these solitons to exist.

Nonstoichiometry could cause many point defects and limit the application of KTP crystal. Nonstoichiometry in KTP and Nb:KTP crystals by high-temperature solution method were studied by laser-ablation inductively coupled plasma mass spectometry (LA-ICP-MS) and X-ray photoelectron spectroscopy (XPS). The formation of high potassium and Ti${}^{3+}$ centers in KTP and Nb:KTP crystals was analyzed. The effect of niobium on nonstoichiometry in Nb:KTP crystal was discussed. The results showed that high potassium, low phosphate, and low oxygen existed in KTP and Nb:KTP crystal samples. Low phosphate and low oxygen in crystal samples resulted from phosphate volatilization, which could be inhibited by the increase of niobium content. Meanwhile, Ti${}^{3+}$ centers in crystal samples were original and formed during crystal growth, and were generated with high potassium simultaneously.

In this paper, we analyze the influence of positive and negative third order dispersion (TOD) on soliton interaction. The peculiar nature of soliton as massive particle results in interaction of in-phase soliton, which has resulted in perfect collision in 160Gbps system at the interaction point, $I_{\mathrm{\text{p}}}=2202.6$Km within one collision period of $L_{\mathrm{\text{coll}}}=4405.2$Km. The TOD normally helps in soliton shift from its initial position. We demonstrate how this shifting of TOD helps in preventing the interaction at 2202.6Km with an initial relative spacing and pulse width of in-phase soliton $q_{\mathrm{\text{o}}}=5.28$ and 1.77ps, respectively. As the TOD has its influence near zero dispersion point of fiber, we choose the dispersion parameter of fiber as ${\beta }_2=0.22$ps²/Km. On considering the positive and negative TOD, the interaction was prevented at $I_{\mathrm{\text{p}}}$, which is characterized in terms of Q-value in a single channel telecommunication system. It is seen that for positive TOD with the values of ${\beta }_3=0.05$ and 0.07ps³/Km, the system yielded the Q-value of 88.33 and 54.81, respectively, while for negative TOD with the values of ${\beta }_3=-0.05$ and $\beta -0.07$ps³/Km, the Q was 84.47 and 38.25, respectively.

Guanidinium trichloroacetate (GTCA), a novel organic single crystal was grown by a slow evaporation technique. The single crystal X-ray diffraction study revealed that the GTCA crystal belongs to tetragonal crystal system with the space group P4₁. From the linear optical studies, the lower cut-off wavelength of grown crystal was found at 257nm. The luminescent study showed that the GTCA crystal has high degree of luminescence. The single shot laser damage threshold of grown crystal is found to be 2.6GW/cm². The nonlinear refractive index, absorption coefficient and third-order susceptibility were estimated by Z-scan technique. The two independent tensor coefficients ${\epsilon }_{11},{\epsilon }_{22}$ of the dielectric permittivity were calculated.

Two-photon absorption and optical limiting of two fluorenyl-based derivatives, 9,9-dimethyl-2,7-bis((E)-4-nitrostyryl)-9H-fluorene and 9,9-dimethyl-2,7-bis((E)-4-((E)-4-nitrostyryl)styryl)-9H-fluorene, in gas phase and solvent with nanosecond laser pulse have been theoretically investigated by solving the coupled rate equations and the field intensity equation employing an iterative predictor–corrector finite-difference time-domain (FDTD) method. The results show that both optical limiting properties and two-photon absorption cross-section strongly depend on the length of these molecules and the solvent. Moreover, the dynamical two-photon absorption behavior is affected by the thickness of samples and the pulse duration. These discoveries demonstrate that these fluorenyl-based derivatives possess highly promising characteristics and have potential applications for optical limiting devices.

We have studied the electronic structure and optical responses of both molecular and bulk phases of 3-nitroaniline (m-NA) using density functional theory (DFT). We have developed our calculations within the framework of band structure theory for both phases. The results of current simulation are also useful for comparison between solids and vapors. Findings show that the crystalline m-NA has an indirect bandgap which is smaller than its molecular counterpart. Due to the weak intermolecular interactions, the crystalline band structure shows very low dispersions and hence the crystalline spectra are very similar to those of molecules, especially at lower energies. This resemblance is extended to lower wavelengths in linear regime, but limited to higher wavelengths in nonlinear one. This study shows that the substituent groups play major roles in the band structure and charge transfer excitations. The optical spectra show higher intensity and more splitting, especially in nonlinear regime, when we go from molecular phase to bulk phase. Findings show that the electron energy loss structures in vapor phase are very close to ${\epsilon }_2$, hence energy loss spectroscopy is a direct way for measuring dielectric function of vapors. According to our results, the crystalline phase exhibits plasmon resonances at much higher energies compared to those of vapor phase. For example, the energy loss spectrum of m-NA molecule shows plasmon peak around 17eV which is about 10eV lower than the crystalline counterpart. The comparison between nonlinear spectra and the linear spectra (as functions of both $\omega$ and 2$\omega$) reveals the significant resemblance between linear and nonlinear structures in both phases. This study shows that the molecular-based models for investigating optical properties of organic crystals are only suitable for low energy regions. Finally, our simulation reproduces the experimental results very well.

Squeezed state of light can present a promising world of quantum communication breaking the quantum limit of noise. We report an all-optical NAND logic operation by dibit representation of squeezed light for a highly noise reduced communication.

This work studies the optical solitons in the physical model that describes the propagation of optical solitons in a medium with competing weakly nonlocal nonlinearity and parabolic law nonlinearity via the $(G^{\prime }/G)$-expansion scheme, exact dark and singular one-soliton solutions, along with the constraint conditions, are reported.

In this paper, ZnO nanorods were grown by wet chemical method on p-Si (100) substrate to form n-ZnO nanorods/p-Si (100) heterojunction. The optical, electrical, structural properties of n-ZnO nanorods/p-Si(100) heterojunction were analyzed by the photoluminescence (PL) spectroscopy, $I$–$V$ measurement, X-ray diffraction (XRD) and scanning electron microscope (SEM), respectively. The room temperature PL spectra reveal the good optical property of the heterojunction with strong UV peak at 385nm. The ZnO nanorods were vertically well-aligned on p-Si (100) and had an average height of about 1.6$\mu$m. The n-ZnO nanorods/p-Si (100) heterojunction also exhibits diode-like-rectifying-behavior.

A highly birefringent photonic crystal fiber (PCF) with large nonlinearity, low dispersion and low confinement loss is designed by introducing a solid elliptical core structure with spiral lattice of circular air holes as a cladding. The dependence of different geometrical parameters, such as pitch size, diameter of air holes and arrangement of air holes are investigated. By optimizing the available parameters, the designed elliptical–spiral PCF offers high birefringence up to 0.005264, high nonlinearity up to 8683.59W${}^{-1}$km${}^{-1}$, low chromatic dispersion of $-9072.62$ps/nm/km, and low confinement loss of 0.00305dB/km within a wide wavelength range of 1000–2000nm.

Vanadium and nitrogen co-doped TiO₂(TiO₂:(V, N)) thin films were fabricated by sol–gel method. Crystal structure, surface morphology, chemical composition and absorption edge of the thin films were characterized by using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS) and UV-Vis spectroscopy techniques, respectively. Photocatalytic activity of all thin films were evaluated by measuring decomposition rate of methylene blue solution under visible light irradiation. The water contact angle analyzer was used to measure water contact angle on the film. The results indicate that absorption edge of TiO₂:(V, N) thin films shifts to visible region. All co-doped TiO₂ samples show higher visible light photocatalytic activity than undoped TiO₂ and single-element-doped TiO₂ counterparts. The best TiO₂:(V, N) thin film can decompose about 90% MB solution and gets super wet state after 150min under compact light irradiation.

In this paper, a novel technique to completely eliminate FWM has been introduced. Alternative circular polarizer have been used to change the polarization of incoming pulses into left-hand and right-hand polarizations before multiplexing in UDWDM optical network with centralized light source. System’s performance have been calculated on the bases of Q factor, optical signal to noise ratio, received power and bit error rate. All simulation has been performed in OptiSystem.