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A one-dimensional photonic crystal structure with a nonlinear metal-dielectric nanocomposite defect layer is proposed to control the optical bistability (OB) of the transmitted wave by tuning the externally applied dc electric field. Using the transfer matrix method for dielectric layers and solving the Helmholtz nonlinear equation in the nonlinear composite layer, the linear transmittance spectrum and the nonlinear transmission curve are illustrated graphically for different applied fields. A field-dependent defect mode is observed in the linear transmittance spectrum. Consequently, the OB switch-up and -down thresholds can be manipulated via the applied field intensity. Due to the field dependence of composite layer refractive index, the physical response of the observation is the dynamical shifting of the defect mode. Moreover, it is shown that the volume fraction, shape, and type of the embedded nanoparticles as well as the kind of the dielectric host have large influences on the OB threshold. The proposed structure has significant potential applications in optical integrated devices. [ABSTRACT FROM AUTHOR]

Low field response function calculations have been performed on a two-dimensional electron gas with well-defined electron-surface roughness scattering. The Lindhard model was employed to compute the response function. In particular, detailed investigations were made on the system searching for an interplay between surface roughness with well-defined correlation function, (characterizes by asperity height and correlation length) spatial confinement and the dielectric function. We analyze to what extent the normal behavior and functionality of dielectric function of two-dimensional devices are modified by random scattering events caused by the contribution from the surface roughness. Results of the current work indicate that contribution of the surface roughness on scattering and absorption process could not be considered as an underestimating effect. We find, however, that functionality of the dielectric function seems to be quite independent of the particular roughness features. [ABSTRACT FROM AUTHOR]

The effect of substrate induced spin-orbit (SO) interaction on the transverse dielectric function of a single plane of graphene has been investigated. The Lindhard model approach was then employed to obtain the transverse dielectric function. The dependence of dielectric function on the SO coupling of the graphene sheet with the substrate was theoretically studied. Numerical results show that increasing the Rashba coupling strength results in a blue shift of the van Hove singularities in the linear dielectric response function. Controllable blue shift opens up ways for a variety of device applications. [ABSTRACT FROM AUTHOR]

The dielectric function of graphene based quantum dot under uniaxial pressure has been studied using the density functional theory (DFT) with local-density approximated (LDA) exchange-correlation functionals. The frequency dependent dielectric function has been obtained and the linear optical properties have been studied. It has been shown that stress results in red shift in which the absorption rate depends on the direction of the polarization and the value of the stress. It has also been shown that the uniaxial stress can remove or decrease the band gap obtained due to the geometrical isolation of the quantum dot. [ABSTRACT FROM AUTHOR]

1D photonic crystal structure contains 16 layers, 8 common dielectric layers and 8 layers with nonlinear medium, with an arrangement similar to the 5th generation, Thue-Morse multilayer is presented. The properties of photonics band gap, field distribution and optical multistability are investigated. On the band gap, 5 resonant modes is observed. On the behavior of output intensity versus input intensity around resonant frequencies, the multistability response observed. When the frequency of incident field is close to the resonant frequency, the threshold intensity of multistability is decreased. [ABSTRACT FROM AUTHOR]

In this paper, transmission spectrum and output intensity profile of a 1D photonic crystal micro-cavity is studied by using the transfer matrix method. It is shown that the transmission spectrum characteristics of the structure irradiated by a Gaussian beam are noticeably different from the plane-wave irradiation transmission spectrum. A ring-shape output intensity profile is observed under irradiation of a common Gaussian beam profile. The various characteristics of output intensity profile are investigated. [ABSTRACT FROM AUTHOR]

The photonic band-gap of the two kinds of 1D photonic crystal structure which is composed of the form of (AB)C(BA), one with a metamaterial defect layer (MDL) and the other one with a dielectric defect layer (DDL) are studied. Our results show that in both cases, where there is only one defect layer, m=1, no defect mode exists, but for two defect layers ( m=2) there is a single defect mode which is centered in the middle of the band-gap. The width of the defect mode in DDL is narrower than that in MDL. For a number of defects of more than two ( m>2) and even, in both of the MDL and DDL structures, there is only one defect mode. For m>2 and odd, the defect mode in the MDL vanishes, but for DDL there is two defect-mode symmetrically centered in the middle of the band-gap. The effects of the defect layers refractive index value, the periodicity number of the structures and the incident angle on the properties of the defect modes and the transmittance spectrum are discussed. [ABSTRACT FROM AUTHOR]

In this work, 40 μm biaxially oriented polypropylene (BOPP) polymer substrate is coated in a roll coater system. The single- and double-coated aluminium thin layers are analyzed by XRD, SEM, TEM, AFM and optical light microscopy. The size and density of pinholes are investigated by using TEM, the size of the pinholes are in the range of 0.8–8 μm, it is shown that with increasing sample thickness, the dimension of pinholes decreases. SEM and AFM are applied to study the surface morphology. The results show that the surface roughness of double-coated film is better than the single-coated one and the size of pinholes is smaller. The transmittance through the samples is measured on the UV–Vis range. The results show that double-coated film has significantly low transmittance (almost zero transmittance) in UV–Vis region. [ABSTRACT FROM AUTHOR]

In this paper, the nonlinear responses and optical properties modification in SK3 glass sample are investigated. The nonlinear responses measurements were performed by using of nonlinear transmission monitoring of 200 fs at 800 nm laser pulses. The optical power limiting threshold of the sample is measured to be about 40 mJ/cm2. The decrease of transmitted intensity is about 63% compared to the theoretical linear transmission at 270 mJ/cm2 incident pulse energy. For prediction of the experimental nonlinear behavior results, a theoretical model based on three-photon absorption and absorption of free carriers is presented. By fitting of experimental data with theoretical model, three-photon absorption coefficient and free-carrier absorption cross-section are reported. The photo-induced optical properties modification of the SK3 sample is investigated also. The modifications that appear as darkening are observed below breakdown threshold intensity. To analyses of modified region sizes, the laser pulse energy accumulation model is applied. [ABSTRACT FROM AUTHOR]

A one dimensional plasma photonic crystal (1DPPC) structure was proposed to design a tunable compressing/broadening multi-channel optical filter with external controllability. The 1DPPC with arrangement of (AP)nD(PA)n, where A and D are the dielectric materials, P is a magnetized plasma layer and n is the number of the periodicity, was proposed. The well-known transfer matrix method was employed for analysis. In linear transmittance spectrum, n1 defect modes were appeared inside the photonic band gap. The results were shown that by increasing the applied magnetic field intensity and its direction, a red-shift and blue-shift were, respectively, observed in defect mode frequencies. On the other hand, the modes were compressed and broadened with increasing the intensity and the direction of the applied magnetic field, respectively. Externally controllable defect modes can be useful in designing a multichannel tunable optical filter. [ABSTRACT FROM AUTHOR]

The effect of linear absorptions on conversion efficiency of the fundamental radiation to the second harmonic wave in a layered structure is investigated under intensity constant approximation. Behaviour of the conversion efficiency after each layer, up to third layer, is graphically illustrated. [ABSTRACT FROM AUTHOR]

In this paper, the effect of a subwavelength thin layer on all-optical diode action in a one-dimensional photonic crystal is investigated. The photonic multilayer structure is considered as (BA)6(AB)6C(AABB)6, where layers A and B are nonlinear and linear materials respectively, and C is a thin layer with positive or negative-index material. The results are shown that by introducing a thin layer with different optical properties the all-optical diode efficiency is controllable. In our numerical results, the transmission contrast of the structure, without the thin layer is obtained as 0.63, with a positive index material layer nearly zero and with a negative index material thin layer about 0.75. [ABSTRACT FROM AUTHOR]

In this paper, the photochromic oxide glass sample under interaction of 200 fs laser pulses at 800 nm wavelength is studied. Two types of laser-induced modifications, bleaching and darkening, are observed. The induced darkening is observed inside the bleached volume. The effect of incident laser shot number and pulse energy on the bleached and darkened area are investigated. The pulse energy accumulation model is applied to investigation of both bleached and darkened area sizes. The bleaching and darkening modification fluence threshold are determined for single and multi-shot laser pulses. [ABSTRACT FROM AUTHOR]

In this paper, the electric susceptibility of a two-dimensional electron gas (2DEG) system in the presence of the Rashba spin–orbit interaction (RSOI) is calculated by using the quantum Liouville’s density matrix method. A controllable blue-shift with increasing RSOI strength at the resonance frequency of the real and imaginary parts of the susceptibility is obtained. We relate this blue-shift to the broadening of the electron energy levels due to the increasing of the RSOI. Increase of the amplitudes and broadening of the real and imaginary parts of the curves with temperature and loss are also demonstrated respectively. [ABSTRACT FROM AUTHOR]

The interaction of the near IR femtosecond laser pulses with photochromic glass sample is investigated. Two different types of microstructures due to the optical properties modification of the sample are observed at the irradiated regions with single laser pulses. Laser fluence and shot number dependency of the structures are investigated. The optical transmission of irradiated areas is analyzed spectroscopically. [ABSTRACT FROM PUBLISHER]