To evaluate Shear Bond Strength (SBS) values of different dental adhesives on Er:YAG laser prepared enamel and bur prepared enamel, one hundred and fifty bovine incisors were randomly assigned to SBS tests on enamel (n=15) in ten different groups. Groups 1 to 5 were prepared with Er:YAG laser. Groups 6 to 10 were mechanical prepared. Followed by: Group 1 and 6 – 37% phosphoric acid (PA) + ExciTE®; Group 2 and 7 – AdheSE®; Group 3 and 8 – FuturaBond® NR; Group 4 and 9 – ExciTE®; Group 5 and 10 – Xeno® V. After the adhesive systems samples were subjected to thermal cycling, SBS were performed in an universal testing machine at 5mm/min. Data were treated with two-way ANOVA, and post-hoc test (Student knewman keuls) (p<0,05). Chi-squared statistical tests were used to evaluate the type of fractures. Mean SBS values were Group 1– 47,17+/-6,25MPa; Group 2–29,10+/-5,21MPa; Group 3–23,32+/ -5,93MPa; Group 4 - 32,56+/-6,36MPa; Group 5– 24,43+/-6,76 MPa; Group 6- 26,12+/-6,32 MPa; Group 7– 14,77+/-3,47MPa, Group 8– 21,03+/-7,44MPa, Group 9– 3,25+/-2,91MPa; Group 10– 16,38+/-7,64 MPa. Statistical analysis of the data revealed that different preparation methods yielded significantly different shear bond strengths. Er:YAG laser preparation of enamel yielded higher bond strengths compared with traditional preparation.
Bulk-size single crystals of the nonlinear optical (NLO) materials: L-tartaric acid (LTA) and L-prolinium tartrate (LPT) were grown from aqueous solution using a home made crystal growth setup. Characterization of the crystals was investigated using single crystal X-ray diffraction. UV-vis-NIR spectra showed that the crystals have excellent transparency in the visible and infrared regions. Tentative assignments were made for the IR absorption peaks. The birefringence of the crystals was measured in the visible region and it was found to be varying with wavelength. Photoluminescence excitation studies showed that the emission occurred at 397 and 375 nm respectively, for LTA and LPT. The second harmonic generation (SHG) conversion efficiency of the powder samples of the crystals were measured as about 40% and 95% respectively, compared to that of the standard KDP crystals.
Spectral-fluorescent characteristics of styrylcyanine dye Sbt ((E)-2-(4-(dimethylamino) styryl)-3-methylbenzo [d] thiazol-3-ium iodide) and its derivatives in aqueous solutions with and without the presence of bovine serum albumin (BSA) were studied. In the presence of BSA for all studied dyes in the absorption spectra, we observed an increase in the absorption intensity, a small broadening, and a new band of the shorter wavelengths with λmax=412 nm. The intensity of the fluorescence emission of the baseband of the studied dyes in the presence of BSA increased from 1.1 to 4.6 times. The binding constant (K) and the number of binding sites (N) of the studied dyes with BSA were determined. The dependence of the binding constant with BSA on the dipole moment of the dye molecules was determined, which indicated that besides electrostatic attraction forces, hydrophobic interactions are significant between styrylcya¬nine dyes with BSA molecules. It was demonstrated that the aggregation of dyes influences the interactions of dyes with BSA.
In this article, we’ve theoretically investigated the application of selective liquid infiltration towards realizing birefringent Photonic Crystal Fiber (PCF) and its operation in the single mode region. Birefringence has been created in a symmetrical structure PCF by infiltrating liquid of certain refractive indices in diagonally opposite air-holes. Different air-hole fraction along with different infiltrating refractive indices has been considered towards studying the effect of the parameters towards birefringence and loss. Cut-off properties for different infiltrating liquid has been performed and it has been found that PCF infiltrated with higher Refractive Indices (RI) liquid is suitable for broader range of single mode operation. The present structure provides very low loss and that can also be minimized with higher number of air-hole rings without affecting the birefringent property. Tunability property of the infiltrating liquid for various temperatures has been studied. By varying the refractive indices of the infiltrating liquid the birefringence can be well tuned. Our research will be useful in designing a birefringent PCF from conventional symmetrical PCF by infiltrating liquids in two diagonally opposite air-holes and proper choice of PCF parameter for single mode operation at a desired wavelength of interest.
Nonlinear material based all-optical switching mechanism is utilized here to develop the all-optical arithmetic operation scheme. Analog optical signals are converted to the corresponding digital signals by optical tree architectures. First a four bit arithmetic unit has been accessed which is elevated to a higher bit arithmetic unit in course. These circuits can execute innumerable arithmetic operations and remarkably, as they are all-optical and fully parallel in nature. These all-optical arithmetic units can gear up to the highest capability of optical performance in high-speed all-optical computers.
We present a new design study of ultra-flat near zero dispersion PCF with selectively liquid infiltration with all uniform air-holes in the cladding towards achieving broadband supercontinuum generation (SCG). With rigorous series study of the optimization process we could achieve near zero ultra-flat dispersion as small as 0±0.41 ps/nm/km for broad wavelength range. The optimized near zero ultra-flat dispersion PCF has been targeted for smooth and flat broadband spectrum supercontinuum generation (SCG) for near Infrared (IR) applications. Broadband SC generations corresponding to three different designs of ultra-flat dispersion fiber have been carried out by using picoseconds pulse laser around the first zero dispersion wavelengths (ZDW). The numerical results show that FWHM of around 400 nm with less than a meter long fiber can be achieved with these fibers that cover most of the communication wavelength bands. The proposed design study will be applicable for applications in the field of tomography, Dense Wavelength Division Multiplexing (DWDM) system and spectroscopy applications etc.
In the article, a model of analysis and an algorithm for calculation of the group velocity dispersion and the losses of light, spreading in a Bragg optical fiber, are proposed. A mathematical model, based on the method of the geometrics optics is included. The influence of the fiber clad dielectric properties on the light propagation is taken into account. A comparison of the dispersion and the bandwidth of fibers with different number layers for low modes are made. Examples of Bragg fibers with different optical properties and attenuation are shown. Finally, advantages of the Bragg fiber, observed on the diagrams of attenuation, dispersion and bandwidth, are listed.
The conversion efficiency of thin film silicon solar cell is still much below that of wafer silicon solar cell due to low optical absorption. Light trapping techniques can enhance the optical absorption in solar cells. Here, we design light trapping structures of double-side grating for ultrathin silicon solar cells based on a rigorous coupled-wave analysis method. The role of each grating was identified by analyzing the absorption spectra of ultrathin solar cell from 350 nm to 1100 nm wavelength at normal incidence, which shows use of top and bottom light trapping structures can achieve large optical absorption in different wave regimes. Inspired by this observation, the dual dielectric/dielectric and dielectric/ metallic grating structures were proposed and optimized to obtain broadband optical absorption close to the theoretic limit.
Exploring experiments of laser thermal shock piston were conducted. The transient temperature of the piston was measured by high-resolution CCD cameras. Temperature of piston can be controlled by temperature-controlled method or time-controlled method. Results show the average temperature of thermal cycles can be improved by increasing heat duration time. There are different temperature response for piston with different preheat temperature in the same laser parameters.
In this paper, a temperature controlled UV-laser lithographic method for the fabrication of integrated-optical polymeric waveguides is presented. The fabricated integrated-optical polymeric waveguides are examined at different processing temperatures. The influence of the temperature on the refractive index depth distribution and thus on the mode field distribution, the number of modes and the effective refractive index of each mode, respectively, is investigated. The refractive index depth profile of the integrated-optical polymeric waveguides is examined by using the Mach-Zehnder interferometric method and an image processing technique. The interference phase differences are extracted in order to determine the refractive index depth profiles of the fabricated optical waveguides. After determining the refractive index depth distribution experimentally, the data of the refractive index depth distribution are employed to calculate the mode field distribution, mode numbers and the effective refractive indices.
The advanced properties of long (~5 mm) plasma plume has been demonstrated for harmonic generation compared with the short (~0.5 mm) lengths of plasmas used in previous studies. The studies of the third and fourth harmonics generation using single color and two color pumps of the long plasmas produced on various metal surfaces are presented. Then the role of heating pulse characteristics on the improvement of harmonic yield from extended plasmas has been analyzed.
This paper reviews the progress of the passive optical network, and discusses a viable means for the realisation of future generation agile gigabits passive optical networks, (GPONs) by the use of low cost narrow band tunable lasers and arrayed waveguide gratings (AWGs). It projectes a two-stage strategy for the realisation of future generation agile GPONs, i.e., the near-term Time and Wavelength Division Multiplexed Gigabits Passive Optical Networks (TWDM-GPONs) and the ultimate Wavelength Division Multiplexed Gigabits Passive Optical Networks (WDM-GPONs). It also presents typical practical designs of narrow band tunable lasers and arrayed waveguide gratings (AWGs) for the agile GPONs.
A diode-pumped Nd:LuVO4 laser emitted at 1086 nm in σ polarization has been demonstrated. A power of 2.37 W at 1086 nm has been achieved in continuous-wave (cw) operation with a fiber-coupled laser diode emitting 18.2 W at 809 nm. Moreover, intracavity second-harmonic generation in cw mode has also been demonstrated with a power of 528 mW at 543 nm by using a LiB3O5 (LBO) nonlinear crystal.
Due to high demand of debris free and high conversion efficiency target for EUV lithography source, We introduce in this article Low-density nanomaterials tin dioxide and tin mono oxide targets for this source. The targets were prepared by refluxing and hydrothermal methods using SnCl2. 2H2O as a precursor. SnO2 spheres like and SnO sheets like images were observed from scanning electron microscopy. The crystal structures of SnO2 and SnO were confirmed by X-Ray diffractions. EUV signal from SnO target at low Nd:YAG energy pulses were more stronger than SnO2.
The intensive effort has made to design new amorphous chalcogenide alloy for the photovoltaic as well as other optoelectronics applications. This work describes a short over view on photovoltaic materials, the relevance of inorganic photovoltaic materials, the development history of Cu (InGa) Se (CIGS) photovoltaics, prospects of chalcogenide photovoltaics. Along with the successful synthesis of Cu20(In14Ga9)Se45Te12 (CIGST-1) and Cu25(In16Ga9)Se40Te10 (CIGST-2) chalcopyrite materials in amorphous form. Structural analysis of the bulk materials was performed from the X-ray diffraction (XRD), Field Emission Scanning Microscope (FSEM), Differential Thermal Analyzer (DTA) and micro Raman analysis. While, the presence of elemental concentrations has been confirmed from the Energy Dispersive Spectroscopy (EDS). Subsequently, thermally evaporated thin films surface morphology and roughness parameter have been analyzed by using the Atomic Force Microscopy (AFM). The 100nm thin films, current-voltage (I-V) and resistance-voltage (R-V) characteristics at room temperature and in the temperature range upto 200℃, under applied voltage range upto 40 V have also been discussed. Outcomes of the structural analysis demonstrates bulk materials have an overall amorphous structure, and their thermally evaporated deposited thin films have low roughness. Structural analysis also reveal bulk CIGST-2 composition has single phase amorphous structure. This material thin film has a smooth surface morphology with a lower and higher values of I and R at room temperature. While, in the temperature range up to 200℃ it has a higher and lower I and R respectively. The physical variation in these materials could be explained with the help of the chemical bond theory of solids.
Synthesis and single crystal growth of nonlinear optical crystal l-threonine zinc acetate (LTZA) is reported and compared with the pure l-threonine in this paper. L-threonine and LTZA crystals are characterized with single crystal and powder XRD, FTIR, UV-Vis-NIR, TG/DTA analyses and SHG test. Single crystals with optically desirable transparency were grown in solution by slow evaporation technique at 35oC using a constant temperature bath (CTB) with an accuracy of ±0.01oC. Single crystal XRD was carried out to examine the crystal system and unit cell parameters. Powder XRD pattern confirms that there is change in the basic structure of materials. The presence of functional groups in the crystal lattice was qualitatively analyzed by FTIR spectrum. Thermal property of grown crystals was reported in the TGA/DTA analyses. Thermal studies revealed that grown crystal LTZA is thermally stable upto 92oC. Optical property of the crystals examined by UV-Vis-NIR studies showed that l-threonine and LTZA crystals are transparent in the range of 200-1100 nm. The second harmonic generation (SHG) efficiency of the LTZA crystal was studied by Kurtz powder method and the efficiency was 3.3 times greater than that of pure KDP and when compared with the parent compound, it was found that efficiency is three times greater than that of l-threonine.
The transmission of four active users has been illustrated with 5 WDM × 4 TDM × 4 CODE channel at 20 Gbps data rate 3 Dimensional Optical Code Division Multiple Access system based on newly designed Model A having signature sequences in temporal domain, spectral domain and spatial domain with optical orthogonal codes, cubic congruent operator from algebra theory respectively, using Galois field GF (5) with varying receiver attenuation on optsim simulation software. The results, numerically shown in terms of bit error rate and graphically represented in terms of eye diagram and signal strength, indicate that the novel 3D coding technique is designed to support four users with good BER with variable attenuation at the front end of the receiver.
This research is an attempt to reduce the gain variation, noise figure and to improve the gain broadness of EDFA by modified mathematical modeling of EDFA for 96 DWDM systems. An improved simulated model of EDFA is specially designed after all the major impairments are taken into account like noise, ASE fiber length, input pump and signal power. The mathematical model of EDFA has been proposed by improving the rate equations of EDFA. Variation of gain versus wavelength has been analyzed with and without ASE. This research claims to support 96 DWDM channels at a channel spacing of 0.8 nm, with a gain of 23.8 dB, ASE of 0.9 dBm for 6 m EDF length for 1479 nm-1555 nm EDFA.
As a factor to limit higher lasing temperature, the rapid lasing intensity degradation in mid-infrared InGaSb/ InAlGaSb quantum well (QW) laser diode has been found and analysed. Due to higher resistance, defects, produced and developed by driving current in p-cladding layer, destroy lattice structure and make the lasing intensity decay. SEM result confirms the defects appeared in p-cladding layer and induced by driving current. Non-radiative recombination induced by defects in the structure is confirmed to result in the optical emission decay at higher temperatures, through the analysis of the electroluminance.
In this paper, a new method for measuring the nonlinear refractive index by using the multiple interference phenomenon occurred in an optical fiber ring resonator (OFRR) is proposed. In OFRRs, input light and circulated light components are added in succession, and then, result in forming a multiple interference output. The OFRR output exhibits nonlinear characteristics between the input and the output power due to the optical Kerr effect, as the input light power increases, as is shown in the bifurcation diagram. In the bifurcation diagram, the output power indicates peaks in the input power range lower than the bifurcation point at which the output changes from stable to periodic state. It is found that the input power at the peak shifts, dependent on the nonlinear refractive index. The nonlinear refractive index can be estimated by applying the measured input power giving the peak point to the numerical relationship between the input power and the nonlinear refractive index. In experiments the nonlinear refractive index of the pure silica core fibers was estimated as n2=1.010-22[m2/V2] and n2=1.110-22[m2/V2] which are in good agreement with those reported previously.
The paper reports new results of chromatic dispersion in Photonic Crystal Fibers (PCFs) through appropriate designing of index-guiding triangular-lattice structure devised with a selective infiltration of only the first air-hole ring with index-matching liquid. Our proposed structure can be implemented for both ultra-low and ultra-flattened dispersion over a wide wavelength range. The dependence of dispersion parameter of the PCF on infiltrating liquid indices, hole-to-hole distance and air-hole diameter are investigated in details. The result establishes the design to yield a dispersion of 0±0.15ps/ (nm.km) in the communication wavelength band. The designed proposed pertaining to infiltrating practical liquid for near-zero ultra-flat dispersion of 0±0.48ps/ (nm.km) achievable over a bandwidth of 276-492nm in the wavelength range of 1.26μm to 1.80μm.
Herein, we present and compare our spectroscopic results on femtosecond (fs) laser irradiated polymers Poly Methyl Methacrylate (PMMA), Poly Di Methyl Siloxane (PDMS) with crystal media such as Lithium Niobate (LiNbO3). Dependence of the structure width with irradiation dose and scan speed is illustrated. Keldysh parameter calculations are highlighted to describe the dominant ionization process. Formation of micro-craters at low irradiation dose and high scan speed is analyzed through minimal pulse to pulse overlap. Formation of defects such as optical and paramagnetic centers in case of polymers is compared with the absence of such defects in crystal media. Confocal micro-Raman studies carried out on polymers and crystal are presented.
We developed a compact and high-power mode-locked fiber laser for multilayered optical memories. The average power and pulse width of the output pulse from the fiber laser that we developed were 109 mW and 2.1 ps, respectively. The dispersion of the output pulse was compensated with an external single-mode fiber of 2.5 m length. The pulse was compressed from 2.1 ps to 93 fs by dispersion compensation. We proposed a fiber confocal microscope as an alignment-free readout system of multilayered optical memories. The fiber confocal microscope does not require fine pinhole position alignment because the fiber core is used as the point light source and the pinhole, and both of which are always located at the conjugated point. The configuration reduces the required accuracy of pinhole position alignment. The fiber confocal microscope can also achieve a compact pickup head. Recording layers in a multilayered medium could be detected with an axial resolution of approximately 900 nm. We demonstrated eight-layer readout with the fiber confocal microscope.
This paper presents an equalization technique of analogue-digital or mixed signals disturbed by electromagnetic interference (EMI) and electromagnetic compatibility (EMC) effects by using negative group delay (NGD) circuit for the microelectronic systems application. The basic principle illustrating the mechanism of the equalization technique thanks to the NGD function is explained. To illustrate the efficiency of the technique understudy, an equalization of RC-effect is performed. According to the frequency- and time-domain analyses, a possibility of the distorted signal reconstruction is demonstrated experimentally and by simulations. To confirm the proposed technique efficiency and reliability, the reduction of rise-/fall-time and propagation delay in relative value more than 90 % is performed by using trapezoidal signal with 1 Gbit/s-rate. It is stated that this technique allows to reduce the signal delays.
The properties and origin of defect modes in the one dimensional photonic crystal (PC) with a central defect has been studied. Two types of photonic crystals, each having single defect, namely, symmetric and asymmetric PCs are considered. It is found that a defect mode arise at central wavelength for asymmetric PC, whereas two defect modes arise in the vicinity of central wavelength for symmetric PC. These two defect modes can be fixed to a single central defect by increasing the width of the defect layer. But the intensities of these defect modes are found to be different from the intensities of defect modes for asymmetric case. The origin of these defect modes can be explained using impedance matching condition. The propagation characteristics of the proposed structure are analyzed by using the transfer matrix method.