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Papers by Farjana Ferdous Tonni

IntechOpen eBooks, Jan 20, 2022

High-performance graphene-HgCdTe detector technology has been developed combining the best proper... more High-performance graphene-HgCdTe detector technology has been developed combining the best properties of both materials for mid-wave infrared (MWIR) detection and imaging. The graphene functions as a high mobility channel that whisks away carriers before they can recombine, further contributing to detection performance. Comprehensive modeling on the HgCdTe, graphene, and the HgCdTe-graphene interface has aided the design and development of this MWIR detector technology. Chemical doping of the bilayer graphene lattice has enabled p-type doping levels in graphene for high mobility implementation in high-performance MWIR HgCdTe detectors. Characterization techniques, including SIMS and XPS, confirm high boron doping concentrations. A spin-on doping (SOD) procedure is outlined that has provided a means of doping layers of graphene on native substrates, while subsequently allowing integration of the doped graphene layers with HgCdTe for final implementation in the MWIR photodetection devices. Successful integration of graphene into HgCdTe photodetectors can thus provide higher MWIR detector efficiency and performance compared to HgCdTe-only detectors. New earth observation measurement capabilities are further enabled by the room temperature operational capability of the graphene-enhanced HgCdTe detectors and arrays to benefit and advance space and terrestrial applications.

Materials Today Physics, 2023

Energy Advances

Two-dimensional layered transition metal dichalcogenides are potential thermoelectric candidates ... more Two-dimensional layered transition metal dichalcogenides are potential thermoelectric candidates with application in on-chip integrated nanoscale cooling and power generation. Here, we report a comprehensive experimental and theoretical study on the...

21st Century Nanostructured Materials - Physics, Chemistry, Classification, and Emerging Applications in Industry, Biomedicine, and Agriculture

Journal of power electronics & power systems, Jul 4, 2018

To increase the unit area illumination of sunlight on solar panels, we design a Field Programmabl... more To increase the unit area illumination of sunlight on solar panels, we design a Field Programmable Gate Array (FPGA) based solar tracking control system. The design mechanism holds the solar panel and allows the panel to perform an approximate horizontal rotation to track the sun's movement during the day. A model prototype solar cell movement system with mechanical assemble is constructed to move the panel from 180 0 East to West. The electronic circuit is designed to sense the intensity of light and to control servo motor for the panel movement. We use the Altera Quartus-II software to perform solar tracking. The design is programmed and loaded into Altera DE1 FPGA board and tested successfully in the laboratory. This system can achieve more illumination and energy concentration than conventional fixed solar panel and can improve overall efficiency.

A self-consistent numerical model is applied to analyze the intensity noise of 850 nm GaAs lasers... more A self-consistent numerical model is applied to analyze the intensity noise of 850 nm GaAs lasers. A systematic technique has been demonstrated to introduce the Langevin noise sources on the photon number and carrier density. The rate equations for photon number and carrier number for semiconductor laser operating in multimode are obtained by considering self-suppression and crosssuppression nonlinear, both symmetric and asymmetric, coefficients. The parameters of the rate equations for GaAs are obtained and the noise effect is described through numerical simulation of the relative intensity noise (RIN). Variations of photon number and carrier number with injection current are also demonstrated. The time varying profile of the fluctuating photon number and carrier number are analyzed. The frequency spectrum of the intensity noise is calculated with the help of fast Fourier transform (FFT). Transient behavior of semiconductor laser is also described that is significant in determining...

Recent experimental investigations in Bi-Layer Graphene (BLG) have shown interesting and useful e... more Recent experimental investigations in Bi-Layer Graphene (BLG) have shown interesting and useful electrical behavior that can be leveraged in building novel device applications. One such behavior being carrier multiplication effects within the BLG. We propose to use a heterostructure of BLG-CdTe-HgCdTe as a detector structure that marries this effect along with the unique bandalignment of the heterostructure which suggest an Ohmic contact for the electrons but a Schottky barrier for the holes. Using a dissipative quantum transport model, namely the Non-Equilibrium Green’s Functions with self-consistent Born approximation accounting for electron-electron and electron-phonon interactions, we calculate energy and position resolved electron and hole currents through these heterostructure and discover a 20X ratio of electron-to-hole ratio in an illustrative simulation which demonstrates the potential for reducing the hole contribution to dark current and modulating the recombination mechanisms and therefore the lifetime of the carriers in the heterostructure.

In this paper, both intensity and phase noise of solitary semiconductor lasers operating in multi... more In this paper, both intensity and phase noise of solitary semiconductor lasers operating in multimode has been analyzed. A selfconsistent numerical model is used for simulation of the rate equations for photon numbers, its phase and carrier numbers for typical 780 nm AlGaAs lasers. Self-suppression coefficient and both symmetric and asymmetric cross gain suppression coefficients are considered in the analysis. We have also considered Langevin noise sources for the photon number, its phase and carrier numbers which induce instantaneous fluctuation in photon and carrier numbers. We have described the noise effect through numerical simulation of the relative intensity noise (RIN) and frequency or phase noise (FN). The photon number and carrier number variations with injection current have been obtained. Laser linewidth has been calculated for different injection current values. The frequency spectrum of the intensity noise is calculated with the help of fast Fourier transform (FFT). Th...

Journal of Power Electronics & Power Systems, 2018

Maximum power demand management is an embedded based project which may be enforced in industries ... more Maximum power demand management is an embedded based project which may be enforced in industries wherever quantity of active load on the idea of critical and non-critical have to be monitored and controlled. Industries are required to use a private controller to dominate these individual parameters. The aim of this project is to use one controller for distributing power from multiple feeders in sequence, just in case of load overflow and use of generator during an absolutely automatic mode on the idea of prioritizing critical and non-critical loads. This project is helpful for power management in industries, schools and large consumers. In many countries, there is an inadequacy of power. Due to this, the electricity board provides solely restricted quantity of energy to the industries, instructional establishments and different large consumers. If they exceed the restricted quantity, they need to pay penalty. The main objective of our project is to share the total dynamic line load for each phase as per the pre defined feeder rating. When the value is exceeded for specific single feeder, the phase will automatically share the load to the other feeders whenever the demand is required. And when the maximum power is used, i.e., overload occurs, the system will automatically start a generator and the parameters will be monitored and controlled by using embedded system.

Dhaka University Journal of Applied Science and Engineering, 2016

International Journal of Scientific & Engineering Research, 2016

—In this paper, both intensity and phase noise of solitary semiconductor lasers operating in mult... more —In this paper, both intensity and phase noise of solitary semiconductor lasers operating in multimode has been analyzed. A self-consistent numerical model is used for simulation of the rate equations for photon numbers, its phase and carrier numbers for typical 780 nm AlGaAs lasers. Self-suppression coefficient and both symmetric and asymmetric cross gain suppression coefficients are considered in the analysis. We have also considered Langevin noise sources for the photon number, its phase and carrier numbers which induce instantaneous fluctuation in photon and carrier numbers. We have described the noise effect through numerical simulation of the relative intensity noise (RIN) and frequency or phase noise (FN). The photon number and carrier number variations with injection current have been obtained. Laser linewidth has been calculated for different injection current values. The frequency spectrum of the intensity noise is calculated with the help of fast Fourier transform (FFT). The transient behavior as well as the steady-state response of semiconductor lasers to varying current input is also analyzed because the transient response is significant in determining the noise characteristics of the laser output. Results show that both intensity and phase noise decreases with the increase of the injection current density. Linewidths have been decreasing substantially with increasing injection current as well.

International Journal of Photonics and Optical Technology, 2016

– A self-consistent numerical model is applied to analyze the intensity noise of 850 nm GaAs lase... more – A self-consistent numerical model is applied to analyze the intensity noise of 850 nm GaAs lasers. A systematic technique has been demonstrated to introduce the Langevin noise sources on the photon number and carrier density. The rate equations for photon number and carrier number for semiconductor laser operating in multimode are obtained by considering self-suppression and cross-suppression nonlinear, both symmetric and asymmetric, coefficients. The parameters of the rate equations for GaAs are obtained and the noise effect is described through numerical simulation of the relative intensity noise (RIN). Variations of photon number and carrier number with injection current are also demonstrated. The time varying profile of the fluctuating photon number and carrier number are analyzed. The frequency spectrum of the intensity noise is calculated with the help of fast Fourier transform (FFT). Transient behavior of semiconductor laser is also described that is significant in determining the noise characteristics of the laser output. Noise characteristics have been studied in terms of the photon and carrier populations as well.