International Journal of Optics and Photonics
Year:2019 | Volume:13 | Issue:2|Papers Count:16

In this study, a sol-gel peroxotungstic acid sol was employed to deposit tungsten oxide (WO3) films by the spin-coating technique. In view of smart window applications, electrochromic windows were then designed and fabricated using a thin tungsten oxide film. For this purpose, Glass/ FTO/ WO3/ electrolyte/ FTO/Glass could be of use due to its special structure that consists of an electrochromic layer (WO3) on a transparent conductor (FTO), an electrolyte containing Li+ cations, and a transparent conductor layer. A voltage was applied on the fabricated sample, which was later assesed for its transmission, switching speed, and coloration efficiency. An increase in the coloration efficiency from 87 cm2/C-1 to 99. 1 cm2/C-1 was found associated with an increase in the deposition speed. Moreover, the increase in the deposition speed led to a decrease in the coloration and bleaching time duration from 11. 4 s to 6. 2 s and from 12. 8 s to 5. 2 s respectively. The results obtained on the thin film WO3 can be useful for electrochromic applications.

The active substrates in surface enhanced Raman scattering (SERS) spectroscopy were prepared through selfassembly of nanoparticles on functionalized glasses. Colloidal silver nanoparticles (Ag NPs) were prepared chemically in two different sizes by reduction of AgNO3 using trisodium citrate and sodium borohydride. Gold– silver core– shell nanoparticles were also prepared to compare between the optical behaviors of their silver shell and Ag NPs. Absorption spectra of nanoparticles were measured by ultraviolet– visible (UV– Vis. ) spectroscopy, and their approximate sizes were determined by dynamic light scattering (DLS). The core– shell nanoparticles were approximately the same size as the largest Ag NPs (35 nm) and had the same maximum absorption wavelength. The potential of these substrates for detection applications was investigated with 1 M and 0. 1 mM solutions of Raman-active molecule of crystal violet (CV) dye. The Raman enhancement signal was recorded for 0. 1 mM solution with 532 nm laser wavelength, and the obtained spectra enhancement factor (EF) was calculated. EF values indicated that although the silver and gold– silver core– shell nanoparticles had the same surface plasmon resonance, the substrate with smaller Ag NPs had the highest enhancement factor compared to other substrates, which was 9. 5 103, and the core– shell substrate even had a slightly lower enhancement factor in compare with the large Ag NPs.

Compared to the long history of plasmonic gratings, there are only a few studies regarding the bandgap in the propagation of plasmonic surface waves. Considering the previous studies on interpretation of plasmonic bandgap formation, we discuss this phenomenon using the effect of both surface plasmon polariton (SPP) and localized surface plasmon (LSP) for our fabricated onedimensional metallic-polymeric grating. This structure is composed of metallic grating on the surface of PDMS with different concentration of embedded gold nanoparticles. By sweeping the incident angles, we have seen that the SPP, LSP and their coupling cause two gaps in reflection regime which are originated from SPP supported by thin film gold film and LSP supported by gold nanoparticles. The first gap is attributed to the patterned metallic film because it vanishes by increasing the nanoparticles which may destroy the pattern while the second gap can be formed by embedded nanoparticles because it becomes more considerable by raising the incubation time. Therefore, the drowning time of patterned samples (e. g. 24h, 48h, and 72h) in HAuCl4 plays the key role in adjustability of plasmonic bandgap. Notably, the interaction between SPP and LSP can be the origin of the shift in gap center from 300 to 550. To best of over knowledge, this study is the first study on the plasmonic band gap as a function of both SPP and LSP.

In recent decades, fiber Bragg gratings (FBGs) have been very much considered for their many applications in optical communication systems, as well as due to their bistability and multi stability properties. In this paper, the formation of ternary stability (TS) in nonlinear chalcogenide fiber Bragg gratings (NCFBGs) is investigated via numerical simulations. Effective parameters on TS such as the FBG length, input wavelength and nonlinear property (or nonlinearity) on TS formation are introduced and studied. It is found that there exists a minimum length for each third order nonlinear coefficient that TS phenomena can be observed. Also, the threshold intensity for TS formation is calculated with respect to the length, input wavelength and third order nonlinearity. In addition, the relevance between the minimum length for TS formation and the third order nonlinearity in the range of chalcogenide nonlinearities are looked into. It is numerically confirmed that increasing the input wavelength (in a valid FBG input wavelength range) increases the TS formation threshold intensity, while decreases the needed FBG length. Because of using experimental values in this paper, it has valuable information about designing the alloptical device with three-level stability which makes NCFBG a suitable option for all-optical ternary switching and all-optical memory in the integrated optical circuits.

In this paper, we have simulated the excitation of wake fields in the interaction of an intensive laser pulses having Half-Sine and Gaussian time envelopes with a fully ionized cold plasma using particle in cell (PIC) method. We investigated the dependency of wake filed amplitude to different laser and plasma parameters such as laser wavelength, pulse duration and electron number density. In addition, the effect of employing a longitudinal magnetic field on the intensity of wake field is studied. It has been seen that the wake field intensity is enhanced in the presence of a magnetic field for both Half-Sine and Gaussian shape pulses. Our aim has been finding optimum values of different parameters for which higher accelerating wake electric fields can be obtained.

In this paper, we proposed an all optical 4-to-2 encoder that has 4 input and 3 output ports. This device generates a 2 bit binary code based on which input port is active. We used nonlinear photonic crystal ring resonators along with optical power splitter for realizing the proposed encoder. In this device the switching rate and area are obtained about 333 GHz and 612μ m2 respectively.

In this paper, a stochastic term is added to the classical generalized nonlinear Schrö dinger Equation to describe the noise generated when light pulses propagate in a fiber. It has been shown that the generated supercontinuum light source fluctuates up to 50% of its output temporal intensity profile due to noises of different sources. The simulation method devised has been applied to the propagation of finite energy Airy pulse in a photonic crystal fiber and to study the generated noise.

We solved one dimensional Schrodinger equation in a H2 + molecular environment by using 3 femtosecond homogeneous and nonhomogeneous laser fields. In homogeneous case, we found out that larger inter nuclear distances result in earlier ionization and also more instability in the wave packet. We deducted that the more the instability is, the more modulated the power spectrum will be. So, by choosing a fixed 1. 96 atomic units inter nuclear distance, we investigated high harmonic generation in both linear and nonlinear nonhomogeneous laser pulses. We observed that in comparison with the linear case, in nonlinear one, the plateau possessed higher intensity harmonics. On the other hand, in this case, cutoff order occurred on higher frequency. By superposing several harmonics near cutoff region, we predicted the generation of a 73 attosecond pulse.

In this paper propagation of combined laser beam through atmosphere is investigated. Laser beam is combined via lens array arrangement. Turbulence is considered as an affecting factor of atmosphere and its effects on transverse coherence length (Fried parameter), peak intensity, propagation efficiency, and spot size of the laser beam is investigated. Coherent and incoherent combined beam are compared. It was seen that irrespective of laser beam quality in weak and medium turbulence levels, propagation efficiency parameter in coherent and incoherent beam combining has almost the same values. Therefore replacing incoherent beam combination with coherent is proposed.

The dynamics of fast gas heating in a high power microwave discharge in air, is investigated in the framework of FDTD simulations of the Maxwell equations coupled with the fluid simulations of the plasma. It is shown that, an ultra-fast gas heating of the order of several 100 Kelvins occurs in less than 100 ns. The main role in the heating is played by the electron impact dissociation of 2 O, dissociation via quenching of metastable states of 2 N, as well as, ( ) 1 O D quenching by nitrogen molecules. Among the electronically excited metastable states, ( ) 2 N B, C, a are the most important species. Slow heating of the gas above 1 μ s is attributed to the vibrational relaxation processes of 2 N, among them vibrationaltranslational relaxation of 2 N demonstrates the highest heating rate. The heating rate and thus the gas temperature are significantly increased with increasing of the microwave pulse amplitude, pulse width, and the gas pressure. In all cases, enhanced 2 O dissociation is the main factor behind the enhanced gas heating. The same effects are observed for increasing of the initial gas temperature, and 2 O percentage in a 2 2 N-O mixture.

A comparative study of antiresonance effects in InSe and InSe doped with GaS, using the resonant Raman spectroscopy is presented. The nonpolar optical phonon of 1 1g A symmetry in InSe exhibits a pronounced decrease in the Raman cross-section at excitation energy 2. 585 eV. In InSe doped with GaS samples, it is found that the anti-resonance behavior decreases as doping contents are increased. To account these observations, a model is applied to explain and interpret the Raman intensity evolution versus incident photon energy. The agreement between theory and experiment is good.

We investigate the medium effect of a parity-time (PT)-symmetric bilayer on the quantum optical properties of an incident squeezed light at zero temperature (T=0 K). To do so, we use the canonical quantization approach and describe the amplification and dissipation properties of the constituent layers of the bilayer structure by Lorentz model to analyze the quadrature squeezing of the outgoing state from the bilayer structure. Our results show that despite the apparent compensation of the losses within the bilayer in the symmetry phase, the outgoing light is no longer squeezed. The results also show that the quantum optical effective medium theory correctly predicts the quantum features of the light outgoing from the PT-symmetric bilayer structure.

stabilized Ag Nanoparticles (NPs) were synthesized using Lee-Meisel method under three different conditions in an oil bath. UV-Vis spectroscopy of the Ag NPs showed a Localized Surface Plasmon (LSP) band around 430 nm, indicating Ag NPs had a size range around 40 nm. To fabricate a surface Enhanced Raman Spectroscopy (SERS) substrate, LSP properties of Ag NPs was employed with the goal of detecting Rhodamine 6G dye. SERS spectrum was recorded by using 180 degrees, back-scatter Raman configuration in a custommade mount. The results showed that ideal Ag NPs agglomeration condition had been achieved by applying centrifuging process and due to this, adding NaCl salt to the SERS substrate was found to be unnecessary. The optimum rate of tri-sodium citrate versus silver nitrate and its influence on UV-Vis and SERS spectra was determined. It was understood that in order to obtain a uniform SERS intensity profile, employing a heater-stirrer instead of an oil bath alongside controlling the atmospheric condition and also drying the substrate in the Argon gas medium are the most necessary conditions for Ag NPs synthesize. The novelty point is obtained when SERS of R6G on a certain substrate, immediately after fabrication and after one month, were compared with a bare R6G dye substrate which, have revealed exceptional performance.

Since Amaranth (AM) is one of the dye compounds which is harmful to human’ s life its removal from industrial waste water would reduce their environmental impact and health effect. Copper nanoparticle (CuNP) is a simple and eco-friendly material which can be used to remove this pollutant. In this paper, copper nanoparticles were synthesized, for removal of AM dye. The experiments were designed by response surface methodology with a modified cubic model to predict the variables. To investigate variables and interaction between them analysis of variance was used with high F-value (1. 44), low P-value (<0. 0409), non-significant lack of fit, the determination coefficient of 0. 898 and the adequate precision of 7. 25. Experimental and predicted values of the response illustrated a good correlation. The optimum parameters catalyst amount (0. 14 w/w%), initial concentration (7. 38 mg/l), reaction time (47. 75 s) and pH (2. 83) for the highest removal percentage of (96. 10%) was attained.

In this paper, an enhancement design of communication system using optical radio frequency (RF) waves in free space optical communication (FSO) system is presented. To our knowledge, it is the first time that the effect of Gamma-Gamma turbulent channel model on the performance of the proposed system is analyzed and simulated. To obtain an optical communication system with good performance and high spectrum efficiency, we proposed two types of optical RF waves including optical single sideband (OSSB) and optical double sideband (ODSB). This strategy that integrated an optical communication system with turbulent channel model can express an accurate model of optical and RF waves propagation in free space. Performance of the system under different regimes, weak, moderate and strong turbulent is studied considering several parameters like max quality factor, bit error rates (BER), and optical signal-to-noise ratio (OSNR). Also, a comparative study between two methods of optical RF waves is presented.

First, this study obtained the fields of an Airy beam (AiB) with optical vortex (OV) for a Fourier transform (FT) system and a fractional Fourier transform (fractional FT) system; thereafter, their intensity and phase patterns were simulated numerically. The splitting on each line of the phase pattern indicates the position of an OV. The results show that the OV position will change when the power of the fractional FT (p) changes. Moreover, the uniformity of the spot beam disappears for the beam with OV. Further, the characteristics of an AiB such as number, width, height, uniformity of the spot beam and the effective beam size will change when there is a change in the values of p and z.