Journal of Nonlinear Optical Physics & Materials

This paper presents the use of a nonlinear microring resonator device known as a modified add-drop filter for small scale conjugate mirror, which is a basic device for 3D image construction and reconstruction system. It can also be useful for real time 3D image display applications. By using the modified add-drop filter, the 3D image can be constructed and reconstructed within the microring circuit. In this circuit, the object and reference beams can be formed by the reflected signals from through and drop ports of the add-drop filter respectively, where the conjugate mirror concept is obtained by the nonlinear coupling effects via the two nonlinear side rings, in which the four-wave mixing of those signals can be introduced. Finally, the interference of those two beams can be constructed and seen by the whispering gallery mode (WGM) at the center ring, while the interference signals can be seen by the add port output. The WGMs of waves are simulated and discussed, where the 3D image construction and reconstruction can be seen by using the microring circuit as the conjugate mirror, in which the use of large volume display using a new type of conjugate mirror can be realized.

Light propagation in a finite nonlinear one-dimensional photonic crystal coated with a metal film is theoretically investigated through the nonlinear transfer matrix method and the finite-difference time-domain (FDTD) method. It is found that the layered structure exhibits both pronounced unidirectionality and high transmission. This leads to all-optical diode actions. Compared with other similar studies, the designed structure has some advantages. First, the structure only with seven periods is much simpler than presented similar structures; second, the structure has both high transmittance and large transmission contrast; third, the perfect performance of AOD is robust to the metal loss.

In this paper, the propagation of Gaussian beam in strong nonlocal logarithmic medium is studied, and the evolution equations for the parameters are obtained. The initial condition of forming spatial optical soliton in this kind of medium, which requires the initial beam on-waist incident and its width equaling to the critical beam width, is different from that in strong nonlocal Kerr medium. The reason of the difference is also analyzed. Moreover, the result shows that the beam width will oscillate periodically when the initial condition is dissatisfied. In addition, we discuss the influence of the initial beam width on oscillating range.

We review recent achievements of high-order harmonic generation in the plasma plumes produced during laser ablation of various materials. These studies have demonstrated the attractiveness of a new approach in coherent extreme ultraviolet radiation generation. We also present the general ideas of potential goals of plasma harmonic studies and perspectives of the development of this relatively new field of nonlinear optics.

In this paper, we continue the theoretical study of changes in optical characteristics of superlattices as a consequence of some specific behavior of excitons. Based on the particular dispersion law and the spectral distribution of excitons, we have formulated and calculated the refractive indices of these structures and defined how refractive indices change with external electromagnetic field. It was determined that among wide variety of parameters governing calculus, only two parameters have a significant effect on exciton energy spectra and calculated optical quantities: (a) the number of film layers which constitute superlattice; (b) ratio of the exciton energy transfer between the layers of one film and on the boundary between two different films.

In this paper we have investigated the dynamics of two cavities each with a two-level atom, coupled together with photon hopping. The coupled cavity system is studied in single excitation subspace and the evolution of the atom (field) states probabilities are obtained analytically. The probability amplitude of states executes oscillations with different modes and amplitudes, determined by the coupling strengths. The evolution is examined in detail for different atom field coupling strength, g and field–field hopping strength, A. It is noticed that the exact atomic probability amplitude transfer occurs when g ≪ A with minimal field excitation probability and the period of probability transfer is calculated. In the limit g ≫ A there exists periodic exchange of probability between atom and field inside each cavity and also between cavity 1 and cavity 2. Periodicity of each exchange in this limit also obtained.

In the present paper, the effect of self-focusing on stimulated Raman scattering (SRS) process by a Gaussian laser beam in collisional plasma is investigated. Due to non-uniform heating, collisional nonlinearity arises, which leads to redistribution of carriers. As a result of which, background plasma density profile in a direction transverse to pump beam axis is modified. This modification affects the incident laser beam, electron plasma wave and back-scattered beam. Nonlinear differential equations for the beam width parameters of the main beam, electron plasma wave, back-scattered wave have been set up by taking full nonlinear part of the dielectric constant of collisional plasma with the help of moment theory approach and are solved numerically by Runge–Kutta method. It is observed from the analysis that focusing of waves greatly enhances the SRS reflectivity.

Potassium iodide doped L-threonine (LTPI) single crystal with improved second harmonic generation efficiency, thermal stability and optical transmission was grown by low temperature solution growth method from aqueous solution. The grown crystal has 1.22 times second harmonic generation efficiency compared to the standard potassium dihydrogen phosphate. LTPI has a high optical transparency over a wide spectral range 245–1083 nm and lower cut-off at around 219 nm. LTPI crystallizes in the orthorhombic crystal structure with space group P2₁2₁2₁. It is thermally stable up to 238°C. In this paper, the photoluminescence study, FT-IR spectroscopic study and elemental analysis have been presented.

We investigate waveguides induced by dark photovoltaic solitons without background beam theoretically and experimentally in LiNbO₃ crystal. Based on sole charge carrier band-transport model, we numerically simulate the transmission equation with shooting method, and find it single mode. Furthermore, we utilize two probe beams detecting the waveguide in experiments: one is continuous with wavelength of 632.8 nm; the other is femtosecond pulse of 800 nm. Comparing the two set of results, we conclude that the waveguides have basic mode only, while the femto-second pulse is more stable. Due to aforementioned stability of waveguide for femto-second pulse, it indicates the possibility of low power continuous beam controlling the high power laser pulse.

In this work, parametric interaction is investigated with the account for phase change of interacting pump, signal and idler waves in the materials of infrared (IR) range of spectrum in case of Zn_1-xMg_xSe crystal. We give an analysis of the threshold intensity of pumping for Zn_0.75Mg_0.25Se crystal under conditions of the existing experiment, as well as the analytical expression for obtaining the optimum value of phase mismatch Δ_opt, at which maximum of signal wave reinforcement is reached. The values of refractive indices, angle of phase matching and angular dispersion coefficient of the first-order for Zn_0.52Mg_0.48Se have been calculated.

Four Wave Mixing (FWM) is a nonlinear process which greatly degrades the performance of the multi-wavelength optical communication systems. This paper describes the analysis of FWM under different all optical modulation formats in two cases of networks such as high nonlinear regime of a 4-Channels, 40 Gb/s WDM network and a normal 32 channel, 40 Gb/s DWDM network. Performance parameters like suppressed FWM side band power, Q-factor and BER are analyzed. Although duobinary, DPSK and DQPSK modulation formats perform better in the latter case, the first case proves that only the DQPSK modulation format performs exceptionally well even in high nonlinear conditions of even DWDM networks.

This paper studies the dynamics of optical solitons in multi-dimensions with spatio-temporal dispersion and non-Kerr law nonlinearity. The integrability aspect is the main focus of this paper. Five different forms of nonlinearity are considered — Kerr law, power law, parabolic law, dual-power law and log law nonlinearity. The traveling wave hypothesis, ansatz approach and the semi-inverse variational principle are the integration tools that are adopted to retrieve the soliton solutions to the governing equation. As a result, several constraint conditions arise out of the integration process and represent necessary conditions for the existence of solitons.

In this paper, the optical phase shift introduced by the fiber Bragg grating is investigated analytically using coupled mode theory. A simple expression for intensity dependent transmittivity as well as optical phase shift has been obtained by incorporating the Kerr effect in nonlinear coupled equations. The behavior is studied as a function of the incident intensity at various detuning wavelengths. It has been found that the nonlinear phase shift increases stepwise with increasing input intensity and such phase modulation of the beam distorts the transmittivity of the grating.

In this paper, we report the fabrication and characterization of an ultraviolet sensing by using Al-doped ZnO films coated on quartz slide and silica fiber optic. Undoped ZnO, 0.5, 1, 2 and 3 at.% of Al were prepared by sol–gel method with annealing temperature of 400°C for 1 h. The presence of spherical shaped nanoparticles and hexagonal (wurtzite) structure were detected for Al doped ZnO by using FESEM and XRD. The band gap values increased by adding Al due to the increment of carrier concentration. I–V curves reveal an ohmic line and improvement in electrical conductivity when the samples are illuminated by ultraviolet (UV) light with a wavelength of 365 nm. At 1 at.% of Al, the film have a larger increment in photocurrent response when illuminated with UV light compared to undoped ZnO and higher concentration (2 at.% and 3 at.%) of Al. For coated fiber optic, the fiber operates under leaky mode and the refractive index of ZnO is decreasing under UV radiation. There is a small drop in output intensity and increased abruptly which depends on the changes of ZnO refractive index. The thin films have a longer recovery time than response time.