Bleaching and Darkening Effect in Photochromic Glasses under Irradiation with Femtosecond Laser Pulses

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

Nonlinear Responses and Optical Properties Modification οf SK3 under Irradiation of Femtosecond Laser Pulses

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/$cm^{2}$. The decrease of transmitted intensity is about 63% compared to the theoretical linear transmission at 270 mJ/$cm^{2}$ 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

IR femtosecond laser microstructuring of photochromic glasses

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

Effect of Linear Absorption on Efficiency of SHG in Layered Structure

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

Enhancement of Photonic Crystal All-Optical Diode Efficiency with a Subwavelength Layer

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 $\text{(BA)}^6$ $\text{(AB)}^6$ $\text{C(AABB)}^6$, 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

Erratum to: Dielectric function of graphene based quantum dot under the uniaxial stress

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

Comparison of photonic crystal narrow filters with metamaterials and dielectric defects

The photonic band-gap of the two kinds of 1D photonic crystal structure which is composed of the form of (AB)N1Cm(BA)N2, 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