Journal of Nonlinear Optical Physics & Materials

This paper reports on the fabrication and characterization of polymer optical waveguide. The polymer films were used by dip coating technique. Various waveguide parameters such as refractive index, optical losses, thickness of guide has been reported. Polycyanurate synthesized as planar optical waveguide exhibits low optical loss (< 2 dB/cm) having refractive index 1.592 and excellent absorption spectra in the wavelength range (1540–1560 nm) which makes this polymer promising for integrated optical devices.

In this paper, we consider the pulse propagation through the birefringent fiber with linear coupling effects. Using the Stokes parameter formalism and conserved densities, we construct the undamped Duffing oscillator equation from integro-differential equations. We also discuss the variation of potential well for different choices of physical parameters. From the linear stability analysis and numerical methods, we also discuss the stability, instability and bifurcation phenomenon in the birefringent fiber through Duffing oscillator type equation.

The dynamics of optical solitons with dispersion-management propagating through optical fibers with damping and amplification is studied. A multiple-scale perturbation expansion method is used to analyze the nonlinear Schrödinger's equation that governs the propagation of such solitons. In this paper we have considered both polarization preserving as well as birefringent fibers. Finally, the case of dense wavelength-division-multiplexed soliton system is also considered.

We report on the investigation of a series of polyaniline based conducting polymers with rather different backbone structure and energy gap in order to explore the effect of their molecular architecture on nonlinear optical properties. In particular, we report on the dispersion of x⁽³⁾(-ω;ω, -ω, ω) in the spectral range covering the rising slope of the optical absorption as well as in off resonance conditions.

The soliton perturbation theory is employed to study chirped solitons that propagate through optical couplers and is governed by the dispersion-managed nonlinear Schrödinger's equation. Here, in this paper, we have considered both kinds of couplers namely twin-core as well as the multiple-core type. In either case, both Gaussian and super-Gaussian solitons are taken into account.

Two-photon absorption spectrum of aniline is recorded using thermal lens effect with optical parametric oscillator as the pump source. Studies show that the two-photon absorption spectrum observed corresponds to ¹A₁ → ¹B₂ transition of aniline.

We describe a modified Z-scan technique for the case when nonlinear refraction is accompanied by nonlinear absorption to separately evaluate the nonlinear refraction and the nonlinear absorption by performing straightforward measurements with the aperture removed. We divide the closed aperture (S < 1) normalized Z-scan by a scan with an open aperture (S = 1). With nanosecond scale at a 532 nm wavelength, we first measured the nonlinear optical absorption and refraction coefficients of a solution of Ni(Ac)₂[N-(8-quinolyl) pyridine-2-carboxamide] · 4H₂O by using the modified Z-scan technique. The nonlinear absorption originates from the near resonant two-photon absorption while the mechanism of the nonlinear refraction is the near resonant two-photon absorption transition enhancement. The linear increasing dependences of the optical nonlinearities on the incident irradiance arise from the population redistribution due to the near resonant two-photon absorption.

The photobleaching of Methylene blue embedded in the solid matrix PMMA (poly(methylmethacrylate)), PVA (poly(vinyl alcohol)) and gelatin has been investigated using a photoacoustic technique. Photoacoustic signals were measured as a function of time, chopping frequency, and the beam power. Experimental results indicate that the photobleaching rate is proportional to the incident laser power (260–300 mW) and decreased with increasing the concentration of dopant molecules. Methylene blue embedded in PVA shows the highest photobleaching rate then followed by gelatin and PMMA. The increase of photobleaching rate in PVA is also noticed when the beam power is increased. The thermal diffusivity values obtained for bleached PMMA, PVA and gelatin are 1.46 × 10^-3cm²/s, 0.83 × 10^-3,cm²/s and 1.10 × 10^-3cm²/s respectively. Spectrophotometer and Raman spectroscopy were used to confirm the photoacoustic results.

In this paper we investigate the propagation characteristics of an end fired Gaussian optical beam through a planar nonlinear waveguide. Using variational formalism we have derived three coupled second order dynamical equations for the beam widths and centre of gravity of the propagating optical beam. Using these equations, we have investigated numerically the beam deflection, displacement and their possible control by nonlinearity. We have shown that intensity dependent control is possible only when the waveguide core possesses nonlinearity and the substrate is linear. In addition, we have demonstrated that such control is not possible in bulk media. We have further established that setting an appropriate length of the waveguide one can achieve maximum displacement with minimum deflection or minimum displacement with maximum deflection. Possible application of our investigation in optical communication and signal processing are highlighted.

The crystals of a new molecular complex, i.e. p-nitroaniline with L-tartaric acid were obtained by slow evaporation of an aqueous solution at room temperature. Room temperature powder infrared measurements were carried out. Tentative assignment for most bands was done. Very strong and broad absorption in the region of 3200–1800 cm^-1 of infrared spectrum is observed. This notable vibrational effect suggests the presence of intense hydrogen-bonded network in the crystal structure of the complex. Second harmonic generation (SHG) efficiency d_eff = 3.85 d_eff(KDP). Some spectral features of this new crystal are referred to corresponding one for two other crystals comprising p-nitroaniline molecule i.e. p-nitroanilinium perchlorate and p-nitroanilinium-p-toluene-sulphonate.