Saghaei's papers published in 2017
[1] H. Saghaei, A. Zahedi, R. Karimzadeh, and F. Parandin, “Line defects on As2Se3-Chalcogenide photonic crystals for the design of all-optical power splitters and digital logic gates,” Superlattices and Microstructures, vol. 110, pp. 133–138, 2017, doi: 10.1016/j.spmi.2017.08.052.
In this paper, a triangular two-dimensional photonic crystal (PhC) of As2Se3-chalcogenide rods in the air is presented and its photonic band diagram is calculated by the plane-wave method. In this structure, an optical waveguide is obtained by creating a line defect (eliminating rods) in the diagonal direction of PhC. Numerical simulations based on the finite difference time domain method show that when self-collimated beams undergo total internal reflection at the PhC-air interface, a total reflection of 90° occurs for the output beams. We also demonstrate that by decreasing the radius of As2Se3-chalcogenide instead of eliminating a diagonal line, a two-channel optical splitter will be designed. In this case, incoming self-collimated beams can be divided into the reflected and transmitted beams with arbitrary power ratio by adjusting the value of their radii. Based on these results, we propose a four-channel optical splitter using four-line defects. The power ratio among output channels can be controlled systematically by varying the radius of rods in the line defects. We also demonstrate that by launching two optical sources with the same intensity and 90° phase difference from both perpendicular faces of the PhC, two logic OR and XOR gates will be achieved at the output channels. These optical devices have some applications in photonic integrated circuits for controlling and steering (managing) the light as desired.
[2] H. Saghaei and A. Ghanbari, “White light generation using photonic crystal fiber with sub-micron circular lattice,” Journal of Electrical Engineering, vol. 68, no. 4, pp. 282–289, 2017, doi: 10.1515/jee-2017-0040.
In this paper, we study a photonic crystal fiber (PCF) with circular lattice and engineer linear and nonlinear parameters by varying the diameter of air-holes. It helps us obtain low and high zero-dispersion wavelengths in the visible and near-infrared regions. We numerically demonstrate that by launching 100 fs input pulses of 1, 2, and 5 kW peak powers with a center wavelength of 532 nm from an unamplified Ti: sapphire laser into a 100 mm length of the engineered PCF, supercontinua as wide as 290, 440 and 830 nm can be obtained, respectively. The spectral broadening is due to the combined action of self-phase modulation, stimulated Raman scattering, and parametric four-wave-mixing generation of the pump pulses. The third and the widest spectrum covers the entire visible range and a part of the near-infrared region making it a suitable source for both white light applications and optical coherence tomography to measure retinal oxygen metabolic response to systemic oxygenation.
[3] A. Ghanbari, A. Kashaninia, A. Sadr, and H. Saghaei, “Supercontinuum generation for optical coherence tomography using magnesium fluoride photonic crystal fiber,” Optik, vol. 140, pp. 545–554, 2017, doi: 10.1016/j.ijleo.2017.04.099.
Supercontinuum (SC) in visible and near-infrared regions is used as a source for optical coherence tomography (OCT) method to measure vascular oxygen saturation in retinal and choroidal circulations. To generate SC in these regions, we first study magnesium fluoride (MgF2) solid-core photonic crystal fibers (PCFs) with submicron air-holes. Then by varying the air-holes diameter we engineer the dispersion and nonlinear parameters as desired. We demonstrate by launching input pulses with center wavelengths of 532 and 640 nm into an engineered PCF, supercontinua as wide as 530 and 580 nm can be obtained that cover the entire visible range and a part of the near-infrared region making it a suitable source for both white-light and OCT applications.
[4] H. Saghaei, “Supercontinuum source for dense wavelength division multiplexing in square photonic crystal fiber via fluidic infiltration approach,” Radioengineering, vol. 26, no. 1, pp. 16–22, 2017, doi: 10.13164/re.2017.0016.
In this paper, a square-lattice photonic crystal fiber based on an optofluidic infiltration technique is proposed for supercontinuum generation. Using this approach, without nano-scale variation in the geometry of the photonic crystal fiber, ultra-flattened near-zero dispersion centered about 1500 nm will be achieved. By choosing the suitable refractive index of the liquid to infiltrate into the air-holes of the fiber, the supercontinuum will be generated for 50 fs input optical pulse of 1550 nm central wavelength with 20 kW peak power. We numerically demonstrate that this approach allows one to obtain more than two-octave spanning of supercontinuum from 800 to 2000 nm. The spectral slicing of this spectrum has also been proposed as a simple way to create multi-wavelength optical sources for dense wavelength division multiplexing.
[5] M. Diouf, A. Ben Salem, R. Cherif, H. Saghaei, and A. Wague, “Super-flat coherent supercontinuum source in As_388Se_612 chalcogenide photonic crystal fiber with all-normal dispersion engineering at a very low input energy,” Applied Optics, vol. 56, no. 2, p. 163, 2017, doi: 10.1364/ao.56.000163.
We numerically report super-flat coherent mid-infrared supercontinuum (MIR-SC) generation in a chalcogenide As38.8Se61.2 photonic crystal fiber (PCF). The dispersion and nonlinear parameters of As38.8Se61.2 chalcogenide PCFs by varying the diameter of the air holes are engineered to obtain all-normal dispersion (ANDi) with high nonlinearities. We show that launching low-energy 50 fs optical pulses with 0.88 kW peak power (corresponding to pulse energy of 0.05 nJ) at a central wavelength of 3.7 μm into a 5 cm long ANDi-PCF generates a flat-top coherent MIR-SC spanning from 2900 to 4575 nm with a high spectral flatness of 3 dB. This ultra-wide and flattened spectrum has excellent stability and coherence properties that can be used for MIR applications such as medical diagnosis of diseases, atmospheric pollution monitoring, and drug detection.