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Bistable Terahertz Switch designed by Integration of a Graphene Plasmonic Crystal into Fabry-Perot Resonator

Mehdi Dehghan, Mohammad Kazem Moravvej-Farshi, Masoud Jabbari, Ghafar Darvish, Mohsen Ghaffari-Miab
Journal PapersIEEE Journal of Selected Topics in Quantum Electronics , Volume 27 , Issue 1, 2021 January , {Pages 4600606:1-6 }


An appropriately designed periodic lattice in graphene can cause plasmonic modes, absorbing a specific THz frequency band, minimizing transmission. A suitable Fabry-Perot cavity, on the other hand, can resonate at another desired frequency in the nearby THz band, enhancing the transmittance. Integrating, these two types of structures into a THz switch, in which the peaks of the plasmonic absorption and the Fabry-Perot resonance band play the role of the OFF and ON states, yielding a bistable switch with a very high output due to the resonance and a high extinction (ON/OFF) ratio. By placing a patterned with an array of circular micro-holes with a plasmonic absorption band centered about 4.1 THz in the middle of a Fabry-Perot vertical cavity

Cation engineering for wide bandgap CH 3 NH 3 Pb (I 1− x Br x) 3 perovskite solar cells

Atefeh Fathzadeh, Bahram Abdollahi Nejand, Mohammad Kazem Moravvej-Farshi
Journal PapersOSA Continuum , Volume 4 , Issue 1, 2021 January 15, {Pages 14-Jan }


We intend to demonstrate that the treatment of MA (=CH_3NH_3) Pb (I_1−xBr_x)_3 perovskites with FA (H_2N-CH=NH_2) cations can enhance the perovskites photovoltaic characteristics. Besides, we propose a new route of bandgap engineering employing low-temperature vapor-assisted solution processes (VASP), reducing fabrication time and material usage. Using this proposed method, we synthesized MAPb (I_1−xBr_x)_3 perovskite layers of 0.4≤x≤1 on mesoporous structures in the ambient atmosphere. Then, we fabricated five types of wide-bandgap perovskite solar cells (PSCs), employing five different molar ratios of PbI_2: PbBr_2, to tune the bandgaps in the range of 1.78 eV≤E_G≤2.29 eV. Then, via spin-coating of FAI and FABr, we introdu

Optical Modulation via Guided-Mode Resonance in an ITO-Loaded Distributed Bragg Reflector Topped with a Two-Dimensional Grating

Sare Vatani, Hussein Taleb, Mohammad Kazem Moravvej-Farshi
Journal PapersIEEE Journal of Selected Topics in Quantum Electronics , Volume 27 , Issue 3, 2021 May , {Pages }


We are reporting the design procedure for a narrow-band ultra-low-power reflective optical modulator that operates at the critical coupling of an appropriately designed two-dimensional grating with the center frequency of a quarter wavelength distributed Bragg reflector (DBR). By sandwiching a three-layer stack of gated ITO/HfO 2 /ITO between the DBR and the grating, we can make the optical modulator operational, taking advantage of the tunable property of the ultrathin layer at the ITO/HfO 2 interface accumulated by electrons under an ultra-low applied voltage (−0.1?V). The corresponding energy consumption is ∼5.5 fJ/bit. Moreover, our simulations show that the capacitance limited modulation speed is more than 80 Mbps. Our numerical r

GNRFET with Superlattice Source, Channel, and Drain: SLSCD-GNRFET

Behrouz Behtoee, Rahim Faez, Ali Shahhoseini, Mohammad Kazem Moravvej-Farshi
Journal PapersPhysica E: Low-dimensional Systems and Nanostructures , Volume 131 , Issue 1, 2021 July , {Pages 114728 }


We are proposing a next-generation graphene nanoribbon field-effect transistor (GNRFET) with superlattice source, channel, and drain (SLSCD-GNRFET), with significantly improved switching performance. The presence of superlattice in each region is for energy filtering. The simulation results indicate that the addition of an appropriate superlattice in the channel region, it reduces the subthreshold swing. Also, using proper superlattice in the drain region leads to an increase of more than a decade in the ION/IOFF ratio by intensely reducing the OFF-current. These improvements make the proposed transistor potentially suitable for the next-generation logical digital applications. Comparison of the simulation results for the proposed SLSCD-GNR

An Integrated 2-bit all Optical Analog to Digital Converter based on Photonic Crystal Semiconductor Optical Amplifier

Sajjad Moshfe, Mohammad Kazem Moravvej-Farshi
Journal Papers , 2021 March 12, {Pages }


In this paper, by integrating InP/InGaAsP/InP Photonic crystal semiconductor optical amplifier (PhC-SOA) with photonic crystal channel drop filters (PhC-CDF), we present a novel fully integrated ultra-small low-power all-optical analog to digital converter (AO-ADC). The self-phase modulation in the PhC-SOA can shift the frequency of the Gaussian input pulse. The two output PhC-CDFs are designed in a way that appropriately codes the frequency-shifted pulse by the PhC-SOA, which consequently converts them to four desired digital output levels. The numerical results indicated that the center wavelength of an amplitude modulated Gaussian pulse with a center wavelength of 1551.228 nm, temporal pulse-width of 10.6 ps, and energy of 74.4 fJ can be

Quantum Optics of Non-Hermitian Optical Systems: Propagation of Squeezed State of Light through Dispersive non-Hermitian Optical Bilayers

E Pilehvar, E Amooghorban, MK Moravvej-Farshi
Journal Papers , , {Pages }


Tunable optical isolator using Graphene-photonic crystal based hybrid system

M Zarei, F Nazari, MK Moravvej-Farshi
Journal Papers , , {Pages }


Thermophoresis suppression by graphene layer in tunable plasmonic tweezers based on hexagonal arrays of gold triangles: numerical study

M Samadi, S Darbari, MK Moravvej-Farshi
Journal Papers , , {Pages }


Exact dispersion relations for the hybrid plasmon-phonon modes in graphene on dielectric substrates with polar optical phonons

S Jalalvandi, S Darbari, MK Moravvej-Farshi
Journal Papers , , {Pages }


Integrated graphene/ferroelectric based plasmonic random access memory (P-RAM)

Masoud Ghezelsefloo, Mohammad Kazem Moravvej-Farshi, Sara Darbari
Journal PapersJournal of Physics: Photonics , 2020 April 30, {Pages }


Using ferroelectric domains in lead zirconate titanate (PZT: PbZr0. 3Ti0. 7O3), we propose and simulate a graphene/ferroelectric-based integrated plasmonic random access memory (P-RAM). The proposed P-RAM poses bistable behavior between two transmission levels when the polarization of the ferroelectric film is switched via tuning an applied bias. Simulation results show that when a voltage applied to a 500-nm long P-RAM is swept from− 1.5 V to+ 6 V and vice versa, the possible extinction ratio is about 18 dB. This integrated P-RAM, operating at a wavelength of 7 ?m, can be used as a memory by measuring two distinct levels of transmission. The proposed integrated memory device, also functioning as a latching plasmonic switch, does not requ

Tuning the Optical Response of Cross-linked Fe@Au Nanoparticles

Najme Ahmadi, Reza Poursalehi, Andrei Kirilyuk, Mohammad Kazem Moravvej-Farshi
Journal PapersApplied Surface Science , Volume 514 , 2020 June , {Pages 165921:1-7 }


We are proposing a novel method to form thin films that are composed of ordered arrays of iron-gold core-shell (Fe@Au) nanoparticles with tunable optical responses. The method is based on the crosslinking of the adjacent Fe@Au nanoparticles using bifunctional group organic molecules. Molecules of m-phenylenediamine (MPD) as conjugated diamines can crosslink the adjacent Fe@Au nanoparticles. Experimental results show that the larger the Fe@Au/MPD mass ratio, the more intense the corresponding plasmon resonance. Images of the optical microscopy and FE-SEM show that there is a tradeoff between the Fe@Au/MPD mass ratio and the formation of ordered arrays of Fe@Au nanoparticles. In particular, Fe@Au/MPD ≈0.4% is the optimum mass ratio for form

Using Superlattice Structure in the Source of GNRFET to Improve Its Switching Performance

B. Behtoee, R. Faez, A. Shahhoseini, M. K. Moravvej-Farshi
Journal PapersIEEE Transactions on Electron Devices , Volume 67 , Issue 3, 2020 March , {Pages 1334-1339 }


Our aim is to improve the switching performance of the graphene nanoribbon field-effect transistors (GNRFETs), exploiting the concept of energy filtering. Within the proposed scheme, a superlattice (SL) structure is used in the source of the transistor for filtering high-energy electron tail by engineering the density of states (DOS). According to simulation results, this can significantly decrease the OFF-current and the subthreshold swing (SS). A comparison of the proposed device with a conventional GNRFET and a graphene nanoribbon (GNR) tunneling field-effect transistor (GNRTFET) demonstrates a significant improvement. Therefore, a typical SL-GNRFET can reduce the average and the minimum of the SS to 44.6 and 12.5 mV/dec, respectively, a

Ultralow-Power Electrically Activated Lab-on-a-Chip Plasmonic Tweezers

Ali Asghar Khorami, Mohammad Kazem Moravvej Farshi, Sara Darbari
Journal PapersPhysical Review Applied , Volume 13 , Issue 2, 2020 February 26, {Pages 024072:1-024072:10 }


We propose ultralow-power plasmonic tweezers with no external optical source. They consist of a one-dimensional array of graphene-based plasmonic units driven by the optical transitions within the underlying array of (Al, In) As/(Ga, In) As/(Al, In) As/(Ga, In) As/(Al, In) As quantum cascaded heterostructures (QCHs), electrically biased in series. Each QCH unit formed in a nanopillar can act as a built-in optical source required for exciting the localized surface plasmons (LSPs) at the surface of the overlying circular graphene nanodisk. The stimulated emission due to intersubband transition within each optical source evanesces through the top (Al, In) As cladding layer and interacts with the overlying graphene nanodisk, inducing the LSPs r

Next-generation on-chip plasmonic tweezer with a built-in light source

Ali Asghar Khorami, Mohammad Kazem Moravvej-Farshi, Sara Darbari
Journal PapersOSA Continuum , Volume 3 , Issue 8, 2020 July , {Pages 2044-2052 }


We are proposing next-generation lab-on-a-chip plasmonic tweezers with a built-in optical source that can be activated electrically. The building block of these tweezers is composed of an Au/p^+-InAs/p^+-AlAs_0.16Sb_0._84 Schottky diode, with a circular air-hole opened in the Au layer. Under an appropriate forward bias, the interband optical transitions in InAs, acting as a built-in optical source that can excite the localized surface plasmons (LSPs) around the edge of the hole. Numerical simulations show that the LSPs mode penetrates a chamber that is filled with water and electrically isolated from the top gold layer, providing the gradient force components desired for trapping the target nanoparticles suspended in the water. Moreover, we

Electronic transport properties of hydrogenated and fluorinated graphene: a computational study

Mohammad Mahdi Khatami, Gautam Gaddemane, Maarten L Van de Put, Mohammad Kazem Moravvej-Farshi, William G Vandenberghe
Journal PapersJournal of Physics: Condensed Matter , Volume 32 , Issue 49, 2020 September 17, {Pages 4600606:1-6 }


Hydrogenation and fluorination have been presented as two possible methods to open a bandgap in graphene, required for field-effect transistor applications. In this work, we present a detailed study of the phonon-limited mobility of electrons and holes in hydrogenated graphene (graphane) and fluorinated graphene (graphene fluoride). We pay special attention to the out-of-plane acoustic (ZA) phonons, responsible for the highest scattering rates in graphane and graphene fluoride. Considering the most adverse cut-off for long-wavelength ZA phonons, we have obtained electron (hole) mobilities of 28 (41) cm2 V−1 s−1 for graphane and 96 (30) cm2 V−1 s−1 for graphene fluoride. Nonetheless, for a more favorable cut-off

Designing an Integrated All-Optical Analog to Digital Converter

Sajjad Moshfe, Mohammad Kazem Moravvej-Farshi, Kambiz Abedi
Journal PapersInternational Journal of Optics and Photonics , Volume 14 , Issue 1, 2020 January 10, {Pages 14-Mar }


We present the procedure for designing a high speed and low power alloptical analog to digital converter (AO-ADC), by integrating InGaAsP semiconductor optical amplifier (SOA) with InP based photonic crystal (PhC) drop filters. The self-phase modulation in the SOA can shift the frequency of the Gaussian input pulse. The two output PhC based drop filters are designed to appropriately code the frequency-shifted analog signals by the SOA, converting them to four desired digital output levels. Our numerical results show that in an appropriately designed AO-ADC, the center wavelength (1572 nm) of an amplitude modulated Gaussian pulse of 1.8 ps width and 1.56 pJ energy can be shifted by 6.7 nm, by the SOA, and then be quantized and coded to four

Tunable Optical Demultiplexer for Dense Wavelength Division Multiplexing Systems Using Graphene–Silicon Microring Resonators

Amin Bagheri, Fakhroddin Nazari, Mohammad Kazem & Moravvej-Farshi
Journal PapersJournal of Electronic Materials , 2020 October 15, {Pages }


An ultracompact tunable optical dense wavelength division demultiplexer (DWDM) compatible with complementary metal–oxide–semiconductor technology is proposed, consisting of a central bus waveguide coupled to two drop waveguides through two ring resonators, all made of silicon (Si). Each Si ring resonator is topped by a graphene microribbon whose chemical potential can be tuned as desired. The center wavelength of each drop channel is determined by the resonant wavelength of the adjacent ring resonator, which in turn is tuned by modifying the conductivity of the graphene. Simulations show that the proposed structure with two graphene–Si ring resonators (GSRRs) having a chemical potential difference of 210 meV demultiplexes a broad opti

Optical modulation based on a graphene-loaded 2D grating

Sare Vatani, Hussein Taleb, Mohammad Kazem Moravvej-Farshi
Conference Papershe 26th Iranian Conference on Optics and Photonics (ICOP 2020), and the 12th Iranian Conference on ineering and Technology (ICPET 2020). , 2020 February 4, {Pages 1149-1152 }


Properties of Bilayer Graphene Quantum Dots for Integrated Optics: An Ab Initio Study

Majid Ghandchi, Ghafar Darvish, Mohammad Kazem Moravvej-Farshi
Journal PapersPhotonics , Volume 7 , Issue 3, 2020 September 22, {Pages 78:1-16 }


Due to their bandgap engineering capabilities for optoelectronics applications, the study of nano-graphene has been a topic of interest to researchers in recent years. Using a first-principles study based on density functional theory (DFT) and thermal DFT, we investigated the electronic structures and optical properties of bilayer graphene quantum dots (GQDs). The dielectric tensors, absorption spectra, and the refractive indexes of the bilayer GQDs were obtained for both in-plane and out-of-plane polarization. In addition, we calculated the absorption spectra via time-dependent DFT (TD-DFT) in the linear response regime. The TDDFT results show that a blue shift occurs in the absorption spectrum, which is consistent with the experimental re

Repositioning of plasmonic hotspots along the sidewalls of conical nanoholes: a numerical investigation

Pooya Alibeigloo, Mostafa Ghorbanzadeh, Mohammad Kazem Moravvej-Farshi
Journal PapersOSA Continuum , Volume 3 , Issue 10, 2020 October 15, {Pages 2817-2829 }


We investigate the plasmonic mode profiles along the depth of various vertical nanoholes to realize vertical nano-manipulation. Our numerical results show that by varying the incident wavelength, we can reposition the plasmonic hotspots along the sidewalls of the staircase and conical nanoholes without and with an oxide spacer. Using the Maxwell stress tensor and the three-dimensional finite difference time domain numerical method, we calculate the optical forces exerted on a polystyrene nanoparticle of 10-nm radius and the related potential energy along the sidewall, demonstrating the trapping sites corresponding to the plasmonic hotspots. Furthermore, the simulation results reveal that adding an oxide spacer of appropriate thickness adds

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