Journal of Nonlinear Optical Physics & Materials

We propose a narrow-dual-band metamaterial perfect absorber (MPA) made of metal-insulator-metal multilayer composite based on the coupling of two resonators. The absorptance of dual resonant peak all exceeding 95% at ${\mathit{\text{l}}}_1=270$nm and 98% at ${\mathit{\text{l}}}_1=290$nm (${\mathit{\text{l}}}_1$ is the length of ‘left’–‘right’ pair), respectively, where the full absorption width at half-maximum is about 3% (low frequency) and 5% (high frequency). The narrow distance of dual resonant peak is 31.4THz together with 43.6THz when ${\mathit{\text{l}}}_1=270$nm and 290nm, respectively. In addition, we demonstrate that the MPA can work as a sensitive sensor for refractive index sensing. The figure of merit FOM* reaches 197.7 (low frequency) and 274.8 (high frequency) when ${\mathit{\text{l}}}_1=290$nm. The narrow-dual-band peak position can be controlled by changing ${\mathit{\text{l}}}_1$ as well.

We report on a wavelength-tunable large-normal-dispersion erbium-doped mode-locking fiber oscillator. By using a grating as spectral filter, the intra-cavity mode-locking spectrum can be tuned continuously. The laser produces 250fs pulses with average power of 130mW and a tunable center wavelength range from 1528nm to 1570nm.

We report efficient second harmonic generation (SHG) of femtosecond (fs) pulses using ZnO nanorods grown by chemical bath deposition (CBD) method with drop-casted seed layer. The SHG behavior of the nanorods are tested using an amplified Ti:sapphire fs laser of pulse duration of 100fs at 800nm. The SHG signal from the ZnO nanorods is found to be of very high intensity as detected by a low cost, compact spectrometer. In a comparative study, the SHG signal from ZnO nanorods grown over seed layer is found to be 12 times higher than the SHG signal observed from the ZnO nanorods grown on substrate without any seed layer. The efficient SHG in former case is due to the growth of high density, well oriented nanorods whereas the lower signal in the later case is due to growth of low density, randomly oriented nanorods. The polarization dependence behavior of the SHG signal is studied both experimentally and theoretically.

The linear and nonlinear optical properties of a defective one-dimensional (1D) graded thickness nonlinear structure are investigated using the well-known transfer matrix method. It is shown that the structure can support a perfect transmission resonance (defect mode) in its forbidden band gap. The frequency of such a defect mode is independent from the value of the thickness modulation parameter. However, its Q-factor decreases and the spatial asymmetry of the structure increases by increasing the thickness modulation parameter. Due to the large spatial asymmetry of the structure, the nonlinear properties of the structure are sensitive to the direction of the impinging light and the structure acts as an optical.

The transmission and reflection properties of a pulse through a slab doped with quantum dots near a plasmonic nanostructure are investigated theoretically. It is found that by adjusting the distance between plasmonic nanostructure and dual quantum dots which is varied from 8.8 nanometer (nm) to 14.4 nanometer (nm) the transmission and reflection spectra for incident pulse through the slab can be modified. Furthermore, it is found that in the presence of plasmonic nanostructure, the reflected and transmitted pulses are completely phase dependent. Therefore, the group velocity of the reflected and transmitted pulses can be switched from slow to fast light by changing the phase difference of two laser fields.

A broadband and polarization-insensitive optical metamaterial absorber (MA) based on the refractory metal chromium (Cr) closed-ring resonator is theoretically investigated. The semiconducting silicon dioxide (SiO${}_2)$ thin film is introduced as the space layer in this sandwiched structure. Utilizing the symmetrical geometry of the proposed MA structure, polarization insensitivity of the broadband absorption is gained. The simulation results show that the absorber with Cr closed-ring array obtains an average absorption of 99.25% from 400nm to 900nm, covering the total visible wavelength range. This compact design may have potential applications in solar energy harvesting, thermal imaging, and emissivity control.

We employ the similarity reductions in two steps to obtain a family of bright and dark similaritons for the variable coefficient cubic–quintic nonlinear Schrödinger equation. Also, parameter domains are delineated in which kink and double-kink similaritons exist for this model. This methodology introduces a free parameter through cubic nonlinearity coefficient which gives us freedom to tune the amplitude and the propagation distance of similaritons in a tapered graded-index waveguide. Furthermore, we observe rapid beam compression of these similaritons for varying detuning parameter and the coefficient of cubic nonlinearity.

A switchable soliton mode-locked and multi-wavelength operation in thulium-doped fiber laser (TDFL) is demonstrated based on nonlinear polarization rotation (NPR) technique. The TDFL produces a soliton pulse operating at 1917.66nm using a 5m long thulium-doped fiber (TDF) as a gain medium as well as nonlinear medium. The solitonic behavior is further identified with two orders of Kelly sidebands in the output spectrum. The mode-locked emission is obtained from threshold pump power of 522–1052mW with consistent pulse repetition rate of 14.7MHz. Maximum pulse energy is calculated as 0.89nJ at pump power of 1052mW, whereas the maximum pulse width is estimated to be approximately 1.36ps corresponding to sech2 pulse profile. By shifting the polarization orientation, the cavity can change to multi-wavelength operation with signal-to-noise ratio (SNR) higher than 53dB. At pump power of 1037mW, three stable peak wavelengths are generated with a power fluctuation and constant spacing of $\pm 1$ dB and 7.4nm, respectively.

In this study, we explore the optical bistability (OB) and multistability (OM) features of probe light propagating in a multiple quantum well (MQW) nanostructure embedded in a dielectric medium. It is realized that via light hole (LH) transition between valance bands and conduction band of MQWs with different electron states, the electron spin coherence can be created which can be used to controlling the OB and OM properties. It is realized that the thickness of dielectric slab can lead to adjusting the threshold of OB in different intensities of input field. Moreover, it is found that the transition from OB to OM or vice versa can be possible by selection of suitable quantity of slab thickness. In addition, the role of relative phase of applied fields on OB and OM manners is discussed in different quantities of thickness. Our results may be suitable for developing nanoscale devices in quantum information science and technologies for future applications.

Using the concept of deformed supersymmetry, we obtain exact localized solutions of nonlinear Schrödinger equation (NLSE) with a number of ${𝒫}{𝒯}$ symmetric potentials and $k$th power-law nonlinearity. Linear stability of these solutions for focusing as well as de-focusing nonlinearity has been examined for various values of the nonlinearity parameter $k$.

Organic nonlinear optical (NLO) single crystal of L-tartaric acid–nicotinamide (LTN) has been grown by slow evaporation solution technique at a constant temperature of 40${}^{\circ }$C. The grown crystals were subjected to various characterization techniques in order to examine their suitability for various applications. Powder X-ray diffraction (PXRD) analysis revealed that the compound is formed without any impurities. Functional groups and formation of the title compound were confirmed using FTIR analysis. Optical behavior of the material was examined using UV–Vis NIR spectrum analysis and the lower cut-off wavelength and optical band gap energy were calculated. Microhardness, dielectric and piezoelectric studies have been carried out at ambient conditions. Electronic properties such as valence electron plasma energy, Penn gap, Fermi energy and electronic polarizability were calculated by Clausius–Mossotti relation. Photoluminescence analysis was carried out to study the luminescence nature of the crystal and its defect states. In addition photoconductivity, etching studies and powder Kurtz and Perry second harmonic generation (SHG) test were carried out.

Soliton solutions are investigated employing the nonlinear Schrödinger equation (NLSE) with an additional term corresponding to an external periodic field. In particular, we use this equation to describe the behavior of solitons in fiber optics in the case of anomalous dispersion. Employing the framework of variational analysis and analytical approximations, single peaked soliton solutions are derived, which exhibit variations of the solitonic parameters due to the effect of the periodic potential and a harmonic oscillator motion of the soliton center, when the frequency of the external field is small, whereas high values of the frequency of the external field produce static solitons. Finally, a variational-numerical analysis was developed and compared with a purely numerical model.

Third-order nonlinear optical properties of tetra-phenyl porphyrin (H${}_{\mathrm{\text{2}}}$TPP) derivatives viz., H${}_{\mathrm{\text{2}}}$TPP(OH)${}_{\mathrm{\text{4}}}$ and Zn(II)TPP doped in boric acid glass thin films were measured using single beam Z-scan and forward degenerate four-wave mixing (DFWM) techniques. Excited state lifetimes and absorption cross-sections were estimated from these experiments. Thickness of the porphyrin doped sandwich glass films were determined using DFWM technique for the first time. The values of nonlinear refractive index ($n_2$) obtained for these systems are are found to be sensitive to the nature of substituents in porphyrin molecule. These results are interpreted in terms of delocalized $\pi$ electrons contributing to the third-order optical nonlinearity.

In this paper, we use semiclassical model to discusse the kinetic electron energy distribution in the single tunnel ionization process of an atom with respect on the pulse duration and the spatial–temporal laser beam distribution. Our theoretical study show that the pulse duration is an important parameter in the ionization process, as well as beam shape.