In this paper, using finite element method (FEM) as a three-dimensional simulation, the light trapping mechanism due to the use of plasmonic core/shell nanorod (PLCS-NR) array as well as its effect on absorption, generation, transfer of carriers and power conversion efficiency (PCE) in a perovskite solar cell (PSC) has been investigated. The short-circuit current density (J sc) increased due to the increase in the carrier generation rate in a PSC with a light-trapping architecture under the normal-angle sunlight (AM1. 5G). Moreover, by choosing gold (Au) and silver (Ag) as the core and CuSCN as the shell in the PLCS-NR, the active layer (AL) absorption is increased compared to the planar structure. Using this proposed structure in the PSC c
In this paper, we propose a new all-optical sensor based on a two-dimensional (2D) regular array of multi-walled carbon nanotubes (MWCNTs) for the refractive index sensing of oil derivatives, for the first time. The interaction of optical wave with the desirable oil derivatives is enhanced using the slow light effect that makes the group velocity go down. We consider the geometric feature for the proposed sensor structure as a photonic crystal (PhC) with a line defect formed by missing some rows of MWCNT elements. The difference of refractive index △n?=?0.1418 between Butanol (C4H10O) and Nitrobenzene (C6H5NO2) host materials results in a wavelength shift of 149?nm, and indicates a sensitivity of 1050?nm/RIU, which can be widely used for
Simulation and investigation of perovskite/nano-pyramidal GeSe solar cell: Realizing high efficiency by controllable light trapping
Masoud Aliyariyan, Davood Fathi, Mehdi Eskandari, Mohammad Hosein Mohammadi
Journal PapersSolar Energy , Volume 214 , 2021 January 15, {Pages 310-318 }
Abstract
Perovskite Solar Cells (PSC) have been elicited much interest within the photovoltaic industry due to their many performance advantages. One of the effective ways to enhance the Power Conversion Efficiency (PCE) of PSCs is to minimize light and electrical losses. To this end, we have focused on the use of nanostructured light absorbers in PSCs and have simulated these structures to understand their effects on the light absorption and electrical output of the cells. Given that perovskites do not absorb light of wavelengths higher than 800?nm, we used an extra absorption material - GeSe – which has a narrower bandgap and a wider absorption spectrum in order to increase the amount of light absorbed. GeSe Nano-pyramids (GSNPs) were also used
Improving the efficiency of perovskite solar cells via embedding random plasmonic nanoparticles: Optical–electrical study on device architectures
Mohammad Hosein Mohammadi, Mehdi Eskandari, Davood Fathi
Journal PapersSolar Energy , Volume 221 , 2021 June 1, {Pages 162-175 }
Abstract
Perovskite solar cells (PSCs) based on lead halide and solution process face issues such as low efficiency and high manufacturing costs. Recently, the emerging field of plasmonics as a branch of photonics has been utilized in electronic, optic and electro-optic devices, which deals with optical phenomena in metallic nanostructures like Au, Ag and Cu. One way to enhance the efficiency is the increase of absorbent layer thickness, while increasing the manufacturing cost. Here, we intend to examine the size, number, and composition of random plasmonic nanoparticles (RPNPs) in the active layer (AL) so that we can increase the power conversion efficiency (PCE) without changing the absorbent layer thickness. The simulation results demonstrate an
Guided-mode resonance filter optimal inverse design using one-and two-dimensional grating
Yaser Khorrami, Davood Fathi, Raymond C Rumpf
Journal PapersJOSA B , Volume 37 , Issue 2, 2020 February 1, {Pages 425-432 }
Abstract
We propose an optimized method for the inverse design of guided-mode resonance (GMR) filters using one- and two-dimensional (1D and 2D) grating structures. This work for 2D state is based on developing the effective permittivity of 1D grating structures along three orthogonal axes to predict the physical dimensions of the structure, for the first time to our knowledge. Also, we compare three optimization methods to reach the optimized conditions based on the characteristics of multilayer structures. Both the transfer matrix method and rigorous coupled-wave analysis are used to simulate and show the reflection and transmission of the proposed 2D GMR filters. The results show that insensitivity to polarization, the best accuracy in resonance
Asymmetric silicon–polymer hybrid waveguide for second-harmonic generation based on modal phase matching
Babak Janjan, Vahid Ahmadi, Mehdi Miri, Davood Fathi
Journal PapersJOSA B , Volume 37 , Issue 2, 2020 February 1, {Pages 376-381 }
Abstract
We propose and design a nonlinear-polymer-filled asymmetric silicon slot waveguide (SSW) for efficient second-harmonic generation. The distinct modal dispersion of the designed asymmetric SSW is used to achieve phase matching between the zeroth-order waveguide mode at the fundamental frequency ($\lambda = {3.1}\,\,\unicode{x00B5}{\rm m}$λ=3.1?m) and the second-order mode at the second-harmonic frequency ($\lambda = {1.55}\,\,\unicode{x00B5}{\rm m}$λ=1.55?m). Simulation results show a conversion efficiency of P_2ω/P_ω=32% with only 10 mW pump power. This high efficiency is a consequence of introducing an asymmetry in the SSW which not only could provide modal phase matching but also preserves high modal overlap between the interacting wa
NiO@ GeSe core-shell nano-rod array as a new hole transfer layer in perovskite solar cells: A numerical study
Mohammad Hosein Mohammadi, Davood Fathi, Mehdi Eskandari
Journal PapersSolar Energy , Volume 204 , 2020 July 1, {Pages 200-207 }
Abstract
In recent years, organic-inorganic hybrid perovskite solar cells (PSCs) have made great progress and encouraged researchers to develop and test many architectures. In this paper, the effect of using NiO@GeSe core-shell nano-rod (NR) array based on the light trapping mechanism on the absorption, generation, collection, and transfer of carriers and finally the overall efficiency of a PSC is investigated using a three-dimensional (3D) finite element method (FEM). By choosing NiO as the core and GeSe as the shell in the core-shell form of NiO@GeSe, the active layer absorption was increased relative to the planar structure. This core-shell structure causes the reduction of carrier recombination within the PSC. Under the normal-angle sunlight (AM
Hybrid SiN Modulator Thermally Triggered by a Graphene Microheater
Babak Janjan, Mehdi Miri, Davood Fathi, Mohsen Heidari, Derek Abbott
Journal PapersIEEE Journal of Selected Topics in Quantum Electronics , 2020 May 22, {Pages }
Abstract
Si N has emerged as a prominent material for expanding the capability of silicon photonics to wavelengths below < 1 μm. However, realizing an efficient optical modulator, a key building block for any integrated optics platform, remains a major challenge in Si N mainly because this material has a vanishing Pockels coefficient. Here, we propose a compact Si N —based optical modulator by using a thin VO2 layer on top of a Si3N4 strip waveguide where amplitude modulation is achieved via phase transition of the VO2 layer. To reduce the actuation time of the temperature-induced VO2 phase transition, a mono-layer graphene microheater is designed for the active Si N —VO2 waveguide. Our simulations indicate a high extinction ratio of?
In an actively Q-switched fiber laser (AQS-FL) a type of acousto-optic modulator (AOM) or (potentially) electro-optic modulator (EOM) controls the generation of output nanosecond wide pulses. An integrated Gaussian pulse shape is desirable in many applications such as material processing, microfabrication, ultrasound generation, gold photothermal therapy, etc. However, because of the system dynamics, generation of perfect Gaussian pulse shapes is not guaranteed in an AQS-FL, additionally designing the AQS-FL for a desired pulse peak and duration is an inverse problem which needs cumbersome trial-error efforts. We have developed a framework consisting of a rigorous FDM method plus a dedicated and innovative multi-objective genetic algorithm
Design of the guided-mode resonance (GMR) grating filter, as one of the most important optical components, using the cultural algorithm (CA) is presented, for the first time. CA is an evolutionary algorithm (EA) which is easy-to-implement, flexible, inspired by the human cultural evolution, upon using the domain knowledge for reducing the search space as a metaheuristic optimization method. Reflection spectra of the designed GMR filter based on the CA is in good agreement with the previous simulation results. CA has both acceptable accuracy and enough high speed to optimize the complicated structures; therefore, a novel double-line asymmetrical transmitter (DLAT) is introduced and optimized as a complex grating-based optical component using
Quasi-Phase Matched Second Harmonic Generation in Plasmonic–Organic Hybrid Structures
Babak Janjan, Vahid Ahmadi, Davood Fathi
Journal PapersJournal of Lightwave Technology , Volume 38 , Issue 6, 2020 March 15, {Pages 1391-1399 }
Abstract
In this article, we propose the design and analyze a plasmonic-organic-hybrid (POH) waveguide structure for efficient forward and backward second harmonic generation (SHG) to bridge the mid-infrared (IR) to near-IR. The required phase matching is satisfied by quasi-phase matching (QPM) technique through periodically altering the material of the metal-insulator-metal slot region between a nonlinear polymer (with second-order nonlinear coefficient of χ^(2) ≠ 0) and Al_2O_3 (with χ^(2) = 0) leading to modulation of χ^(2) coefficient along the propagation direction. The strong field confinement offered by surface plasmon polaritons (SPPs) significantly enhances the normalized efficiency up to 1.75 ? 10^6 W^−1cm^−2 in the case of backwa
Design and simulation of perovskite solar cells based on graphene and TiO2/graphene nanocomposite as electron transport layer
Mehran Dadashbeik, Davood Fathi, Mehdi Eskandari
Journal PapersSolar Energy , Volume 207 , 2020 September 1, {Pages 917-924 }
Abstract
In recent years, investigation on utilizing perovskite solar cells (PSCs) has become widespread and much researches have been conducted to increase the power conversion efficiency (PCE) and sustainability of this type of solar cell. In this research, the effects of graphene (Gr) and TiO2/Gr nanocomposite as the electron transport layer (ETL) on the absorption, carriers generation and recombination, carrier transport, short-circuit current density (Jsc), open-circuit voltage (Voc) and PCE are investigated. For this purpose, a three-dimensional (3D) finite element method (FEM) technique is utilized. Using the monolayer Gr ETL, the absorption in the active layer enhances and Jsc increases from 19.07 to 21.73?mA/cm2. Meanwhile, Voc decreases fr
Journal PapersIEEE Transactions on Instrumentation and Measurement , 2020 July 27, {Pages }
Abstract
In this study, a portable optical instrument was designed and developed for real-time non-destructive determination of fruit ripeness. A prototype of the instrument using inexpensive parts, was developed and calibrated for apple ripeness detection based on moisture content, Soluble Solids Content, pH and firmness. An array of 6 optical point sources (LEDs that emit light at 520, 670, 920, 970, 1050 and 1320 nm wavelengths) were selected using Vis/NIR spectral analysis on apple samples. The instrument was equipped with optical fibers, optical sensors and an Arduino board for sending and the receiving the waves and processing the received signals as well as controlling the operation of the instrument. The decision tree method was utilized to
Low-Voltage Electrically-Induced Second Harmonic Generation in a Silicon Waveguide with Embedded pin Diode
Babak Janjan, Vahid Ahmadi, Davood Fathi
Journal PapersJournal of Lightwave Technology , 2020 July 21, {Pages }
Abstract
Design and analysis of a silicon waveguide with embedded pin diode is proposed here for realization of the second harmonic generation (SHG). The reverse-biased pin structure is employed to apply a DC field across an intrinsic silicon region which gives rise to electric-field induced (EFI) second-order nonlinearity (2)EFI in silicon. The resulted (2)EFI is then used to generate a second harmonic (SH) frequency of an input 2.29-m signal in which second-order mode at 1.145 m is used to attain modal phase matching with fundamental mode at 2.29 m through suitably designing the silicon waveguide. It is shown that by engineering the geometry of pin diode, not only a high modal overlap integral is yielded by completely eliminating the counteractive
In this paper, coupled optical and electrical simulations of perovskite solar cells (PSCs) are performed to optimize their basis output parameters and obtain the best power conversion efficiency (PCE) based on both the light absorption and carrier transport mechanisms. Due to the limitations of perovskite absorption in longer wavelengths, we used an extra photo-active material of GeSe with a narrower bandgap and a broader absorbing spectrum to increase the efficiency of the PSC. To prevent carrier transmission disorder that exists in the planar structure with two absorbing materials, GeSe was inserted into the main active layer in the form of nanowires (NWs). As a result, it improved the carrier transfer and open-circuit voltage (V oc) in a