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Go to Editorial ManagerPorous Silicon (PSi) samples with (100) orientation n-type were prepared by photo-electrochemical etching process for different variable parameters and fixed electrolyte solution HF:C2H5OH:H2O (2:3:3). Physical and optical properties of PSi would be varied with the variation of process parameters such as current density, anodization time and laser wavelengths. Two types of 50 mW diode lasers were chosen, 473 nm Blue & 532 nm green at 20 mA/cm2 & 15 min etching time to assist the iodization process. The band gap of the fabricated layer has raised up to (2.9 eV) which is more than twice its original value for the c-Si (1.12 eV). _x000D_ Exploiting the obtained gap energy values, the refractive index of porous silicon layer was calculated depending upon Vandamme empirical relation. It was observed that the porosity is modifiable through etching conditions, which in turn makes refractive index also modifiable. Thus, the calculation depended on taking certain parameters as the current density and etching time in order to compare the effect of applying the two laser wavelengths. AFM was applied to observe the homogeneity and roughness of the PSi mono-layer. The results are in a very good agreement with the range of the refractive indices of PSi and the illumination with green laser gives a better conclusion to use in solar cells as a good absorber and a bad reflector.
This research introduces a method of an electro-optic effect and electro-refractive effect that considers very imperative for high-speed optical communication systems. In this research, it presents way by a reduction the gap between the electrodes d, and this technique achieves to solve the problem of overlap for Mach-Zehnder interferometer MZI electro-optical switch base on lithium tantalite LiTaO3, also this technique suggests a model for analysis the effect parameters on the electro-optic overlap of the electro-optic switch as the ordinary positive changing of refractive index and a length of arm switch. This study achieves a better overlap by large positive changing refractive index with a suitable small length of arm about 8µm and low driving power at least 4V/µm. Also, for lithium tantalite LiTaO3, this research achieves a better performance for system using the near infrared wavelength.
A high-performance Mach-Zehnder interferometer (MZI) based all-optical switch using graphene on silicon nitride (Si3N4) is proposed and simulated. Graphene absorbs pump power (λ = 980 nm) on Si3N4 waveguide, generating heat. The heat affects the Si3N4 waveguide, causing a change in its refractive index due to thermo-optic effect. By tuning the probe phase (λ = 1550 nm) in the Si3N4 arm with graphene on top, all optical switching can then be carried out. An extinction ratio ranges of 13-25 dB and pump power range 20-270 mW. These findings demonstrate that our suggested configuration offers a useful integrated part for the creation of effective all-optical control devices on the insulator platform with a quick switching rate. Moreover, the suggested design might be able to achieve a wide bandwidth by utilizing an integrated MZI structure.
In this work, a sensor for cooking oils was designed and fabricated for the first time using hollow-core photonic crystal fiber (HC-PCF). This sensor was studied practically, and the results showed a difference in sensitivity depending on the type of oil. The results showed that the wavelength shift occurred with very small changes in the refractive index of the edible oil. The confinement loss was computed. Seven oils with various refractive indices were utilized. Based on our results, the relative sensitivity to various kinds of Canola oil, Sunflower oil, Olive oil, Walnut oil, Sesame oil, Corn oil, and Wheat oil are 79.9321%, 80.1588%, 77.4523%, 77.4889%, and 77.5650%, 77.6652%, 80.5902% respectively. Moreover, the proposed sensor also has low confinement losses of 6.473×10-9dB/m, 1.158×10-9dB/m, 1.2×10-9dB/m, 1.20×10-9dB/m, 1.199×10-9 dB/m, 1.2×10-9dB/m, and 6.347×10-9dB/m respectively. This sensor can be used to measure the quality of oils and distinguish their types, and they can be a practical element in oil detection systems, which will bring about a change in the future in oil detection methods.
In this paper, we suppose a method for reducing the dispersion in the plastic optical fiber (POF) Bragg gratings based on optimizing the grating coupling-strength (?) using genetic algorithms. The effects of average refractive index (?n) and temperature (T) change on the dispersion properties are investigated numerically. It is found that the amplitude of the ?n for low dispersion performance needs to be reduced at the cost of the design complexity of the POF Bragg gratings. Owing to the unusually large and negative thermo-optic coefficient of the POF, the dispersion due to the wavelength shift induced by the temperature variation will be reduced by operating at high ? value. Results showed that by optimizing the ? value a very large dispersion reduction range has been obtained, from 1178 to 11.5 ps/nm at 30 mm grating length.
Whispering Gallery Mode Micro-Resonators (WGMRs) have received significant interest due to their great sensitivity to environmental changes, compact size, and ability to operate over a wide spectral range because their low optical losses produce high-quality factors so that they can be used in various sensing applications. This work investigates the design and implementation of cylindrical WGMRs for Refractive Index (RI) sensing for different delivery fiber diameters. Single Mode Fiber with different waist diameters (80,67.1,18) µm were used as delivery fibers. At the same time, the sensor (resonator) fiber is SMF with a diameter (125 µm). Quality factors and Free Spectral Range (FSR) were calculated and analyzed for each diameter. The quality factor for all diameters was in power of 104, which is considered good. The FSR is inversely proportional to fiber diameter. FSR values were (0.678,1.75,2.03) nm for (80,67.1,18) µm delivery fiber diameters respectively. An analyte prepared by NaCl with different refractive indices is used to investigate the RI sensor performance. Higher sensitivity is obtained from the WGMR with a smaller waist diameter, which is (-)74 nm/RIU. While for the delivery fiber diameters (80,67.1) µm were (-0.28, -9.27) nm/RIU respectively. The submitted sensor will have a good contribution in the field of chemical, biological and medical applications.
The aim of this work is to use Fiber Bragg Grating (FBG) to detect the breast cancer at its earliest stages based on the Photoacoustic (PA) hybrid technique. The fiber Bragg gratings sensitivity to acoustic wave, effect of grating length, effect of grating refractive index modification, and ultrasonic frequency on the wavelength sensitivity and intensity sensitivity of the ultrasonic sensor (FBG) for ultrasonic waves were investigated using a simulation programs. A wavelength for the photoacoustic (PA) excitation laser was chosen with respect to a high absorption by the tumor and with low absorption to the surrounding tissue (normal tissue); for higher contrast absorption between them. Fiber Bragg can be used as a sensor to detect the acoustic wave emitted from the tumor (depending on the photoacoustic principle). In this study, k-wave a MATLAB toolbox was used to simulate photoacoustic wave which is detected with fiber Bragg grating simulation, using Optisystem program. The acoustic wave was transferred to FBG by using Optisystem-MTLAB communication programs to detect tumors.
The effect of metal nanoparticles (MNPs) on the electric field strength and distribution for improvement solar cell performance is investigated and simulated. By manipulating the properties of nanoparticles, distribution of the electric field was altered. In this paper, classical solar cell (p-n junction) and improved structure (add an extra layer of SiO2 and gold nanoparticles on the top of p-n junction) is simulated. Different sizes of NPs, thickness of SiO2 sublayer, and spacing distance between NPs is done to improving the electric field and showing plamonic effect. Gold NPs deposition on single crystalline silicon solar cell is modelled by COMSOL 5.2 2D, Electromagnetic wave propagation in the frequency domain with periodic boundary conditions. The best wavelength found in our work is 550 nm. The electric field enhances when the size of NPs increases but it must be limited. When gold NPs are deposited on the SiO2 sublayer, the plasmonic effect appears due to decreasing the refractive index. Moreover, separation distance between NPs affect the electric field enhancement by manipulating the number of NPs, the distance decreases and the plasmonic interaction appears.