# Nikhil Ranjan DasUniversity of Calcutta · Institute of Radio Physics and Electronics

Nikhil Ranjan Das

PhD

## About

165

Publications

9,795

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610

Citations

Citations since 2017

Introduction

Nikhil Ranjan Das is presently a Professor at University of Calcutta in the department Radio Physics and Electronics. His field of interest: modelling & design of optoelectronic and nano electronic devices.

## Publications

Publications (165)

The present work proposes a new, to the best of our knowledge, approach of hetero-cladding for silicon photonic waveguides and outlines its contribution towards realization of a compact directional coupler. The proposed hetero-cladding, comprising ferroelectric B a T i O 3 and S i O 2 , helps control the distribution of modes and evanescent modes i...

In the present literature, an attempt has been made to understand the birhythmic behaviour of a modified time delayed Dual Loop Optoelectronic Oscillator (DLOEO). To this end, an analytical solution of periodic oscillation is obtained using weakly nonlinear analysis. Two coexisting periodic oscillations are identified, considering shorter loop dela...

This paper presents an analytical method to investigate the impact of component crosstalk on the spectral efficiency (SE) of generalized quadrature phase shift keying (QPSK) modulation format by computing its bit error rate (BER) over additive white Gaussian noise (AWGN) channel. For this purpose we consider a wavelength division multiplexed (WDM)...

We study the electron transport in armchair graphene nanoribbon (AGNR) resonant tunneling diode (RTD) using square and V-shaped potential well profiles. We use non-equilibrium Green’s function formalism to analyze the transmission and I-V characteristics. Results show that an enhancement in the peak current ( I p ) can be obtained by reducing the w...

We report an Aubrey-André-Harper (AAH) model based quasi-periodic lossless evanescently coupled waveguide lattice to study the unconventional physics of light localization. We find an exclusively new way to establish localization phase transition in a 1D-AAH lattice by observing the slope variation of the band and accordingly study the modal charac...

In this letter, we propose a new approach of hetero-cladding for realization of compact CMOS compatible silicon photonic directional couplers. The proposed hetero-cladding comprises ferroelectric BaTiO<sub>3</sub> (BTO) and SiO<sub>2</sub> to control the evanescent mode within the structure. The results show very small and identical coupling length...

In this letter, we propose a new approach of hetero-cladding for realization of compact CMOS compatible silicon photonic directional couplers. The proposed hetero-cladding comprises ferroelectric BaTiO<sub>3</sub> (BTO) and SiO<sub>2</sub> to control the evanescent mode within the structure. The results show very small and identical coupling length...

In this paper, design strategies for enhancement of efficiency for biosensing using optical microring resonator are described. Medical diagnostics play a crucial role in healthcare as it aims to provide early diagnosis of diseases. This urges the need to design an efficient point-of-care diagnostics to improve healthcare technologies. Among the exi...

In this paper, the spectral efficiency and quantum limit for transmission of a BPSK signal in a WDM system are computed after analyzing the error probability in the presence of component crosstalk. The analysis of bit error rate (BER) is derived from the non-Gaussian probability density function for finite (N) interferers obtained using a new mathe...

We report an Aubrey-Andre-Harper (AAH) model based quasi-periodic lossless evanescently coupled waveguide lattice to study the unconventional physics of light localization. We present an exclusive methodical analysis of the band-topology of a tight-binding discrete lattice and accordingly study the modal characteristics to reveal the fact that a hi...

p> Abstract — The present work proposes a new approach of hetero-cladding for silicon photonic directional couplers and outlines its contributions towards realization of a compact, tunable and energy efficient directional coupler. The proposed hetero-cladding comprises ferroelectric BaTiO<sub>3</sub> (BTO) and SiO<sub>2</sub>, to control the evanes...

p> Abstract — The present work proposes a new approach of hetero-cladding for silicon photonic directional couplers and outlines its contributions towards realization of a compact, tunable and energy efficient directional coupler. The proposed hetero-cladding comprises ferroelectric BaTiO<sub>3</sub> (BTO) and SiO<sub>2</sub>, to control the evanes...

This paper presents a study on the propagation of modes of electromagnetic wave through a homogeneous multicore fiber. Complete view for fundamental modes for each core and other linearly polarized modes are obtaining here. Coupling between fundamental modes and other different cladding modes are presented in this paper. This study includes the cou...

Waveguide structure having a rectangular trench on top of its core has been studied. Variation of optical power overlapping with cladding of the waveguide has been shown as a function of trench dimension. Appropriate dimension for the trench to obtain large amount of optical power in the cladding has been shown, and the reason has been discussed. U...

The study presented in this paper has been focused on the investigation of the WDM receiver performance in presence of the nonlinear crosstalks—namely, stimulated Raman scattering and four-wave mixing—and, hence, suggesting optimum detection thresholds to minimize bit error rate. To calculate the bit error rate, good representative models which are...

In this study, the distribution of photons within a quantum dot (QD) light-emitting diode (LED) structure is presented by solving steady-state rate equations. The results show that the total photon density within the structure is distributed in a nonlinear manner along the direction of light propagation. Then the variation of photon density, contri...

Sensors used for biological and chemical sensing have been active research topics because of several potential applications like medical diagnostics, environment monitoring, etc. Among the existing sensors, integrated optical waveguides based sensors making use of photonic microring resonators possess a promising performance. When light propagates...

This book gathers selected research papers presented at the 7th International Conference on Computers and Devices for Communication (CODEC 2019), held at the Department of Radio Physics and Electronic, University of Calcutta, India, on 19 – 20 December 2019. It includes recent research in the field of nanomaterials, devices and circuits; microwave...

We present a quasi-periodically modulated coupled multicore fiber based on Aubry-Andre- Harper model to exhibit a sharp localization phase transition that is explicitly dependent on modulation strength and core arrangement radius of the geometry.

We present a theoretical study on gain and bandwidth of a CMOS-compatible submicron multi- diode Si avalanche photo-detector suitable for operation at high speed and moderate voltage. A two-dimen- sional model is used to obtain the avalanche build-up of carriers in the depleted region considering the dead- space effect. The regions between fingers...

A model for quantum dot (QD) superluminescent light emitting diode (SLED) is presented to study an optical power output and linewidth over a wide range of injection currents. The analysis is based on the photon and carrier rate equations including the effects of homogeneous and inhomogeneous broadening, carrier escape process, and high-current heat...

A study on the transient behavior of a single-loop optoelectronic oscillator (OEO) under a single sinusoidal radio frequency (RF) signal injection is presented. Considering only the phase perturbation imposed by the external RF signal, the phase-dynamic equation is solved to analyze the frequency settling behavior of the loop. A closed form express...

Quantum efficiency of CMOS compatible multi-diode lateral Si p–i–n photodetector is calculated using two-dimensional transport in the form of carrier diffusion from substrate along the vertical direction and drift along the horizontal (lateral) direction. The model verified with experimental data from literature are used to compute and plot the qua...

[Full text: https://rdcu.be/b4ovR] Neuromorphic architectures merge learning and memory functions within a single unit cell and in a neuron-like fashion. Research in the field has been mainly focused on the plasticity of artificial synapses. However, the intrinsic plasticity of the neuronal membrane is also important in the implementation of neurom...

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

In this paper, a new, to the best of our knowledge, design for a ferroelectric BaTiO3 cladded silicon photonic phase shifter with very small switching length for compact photonic integrated circuits (PICs) is proposed. The proposed design is based on the choice of a waveguide core with suitably slanted sidewalls in order to favor the desired polari...

This paper brings the results of a study of the frequency pulling in a single loop optoelectronic oscillator (OEO) when injected by weak and strong radio frequency (RF) signal. An experiment was performed for three different injection signal powers to study the frequency pulling and the average frequency of the OEO. The analysis is made on the basi...

An approximate strong injection perturbation mathematical model to analyze the frequency pulling and non-linear dynamics in radio frequency (RF) signal driven optoelectronic microwave oscillator (OEO) is presented here. The formulas regarding the lock-range, the beat frequency and the average frequency are derived, which help to estimate the amount...

In this paper, a machine learning (ML) based approach is described to design a photonic crystal (PhC) gas sensor for identification and estimation of three greenhouse gases, namely SF6, CH4 and CO2. Exploiting the refractive index dependence of the defect layer positions in the photonic bandgap (PBG) in the transmission spectrum of a PhC, structure...

We present a model to investigate the local change of the refractive index of a ferroelectric material employed as upper cladding of silicon photonic waveguides. The model is used to predict the saturation voltage required to achieve complete domain switching in case of a BaTiO3 film and to evaluate the performance of non-volatile phase-actuators i...

The present literature reports the effect of an external synchronizing signal on the chaotic dynamics of a single Loop optoelectronic Oscillator (SLOEO). We have applied an external periodic signal in a chaotic optoelectronic oscillator (OEO). The OEO can produce chaotic oscillation with small change of feedback loop delay. It has been observed tha...

In this paper, 1D Photonic Crystal structure, consisting of alternate layers of silicon and air, is theoretically studied for gas sensing application. With one of the air layers replaced by a different gas layer, the resulting defect mode can be utilized for sensing a particular gas, from the transmittance curve, calculated by Transfer matrix metho...

A comparative study on power penalty due to component, SRS, and FWM crosstalk in a WDM receiver is presented in this paper. The relevance of such crosstalk phenomena is analyzed depending upon various parameters and domains of operation. Power penalty is examined as a function of the number of interfering channels to compare the receiver performanc...

Photonic micro-ring resonators can be used as sensor which finds promising bio-analytical applications. The light propagating through the micro-ring and the resultant evanescent field beyond the structure are sensitive to the refractive index of the environment. This sensing capability can be used for detection of biological targets. In this paper,...

A silicon photonic directional coupler with ferroelectric cladding has been studied. It is shown that the domain switching in ferroelectric material can be utilized to reduce continuous power consumption and thermal noise in dense photonic integrated circuits when compared to conventional thermo-optic actuators.

We investigate the dynamics of a modified optoelectronic oscillator (OEO) through theoretical and numerical analysis. The OEO under study is different from the conventional OEO in the sense that it contains a van der Pol oscillator (VDPO) in its feedback loop, in place of the RF band pass filter. Two coexisting limit cycle oscillations are identifi...

In this paper, optical gain of quantum dot ensemble is investigated in presence of external electric field for different carrier densities. First, the wave functions and the energy eigenvalues of carriers are calculated by solving the Schrödinger equation for a quantum dot. Then these electric field dependent wave functions and energies are used to...

This paper analyzes the phase-locking phenomenon in single-loop optoelectronic microwave oscillators considering weak and strong radio frequency (RF) signal injection. The analyses are made in terms of the lock-range, beat frequency and the spectral components of the unlocked-driven oscillator. The influence of RF injection signal on the frequency...

We numerically investigate the hysteresis properties of domain switching in a BaTiO3 film to realize compact non-volatile phase actuators integrated in silicon photonic waveguides.

In this paper, an approach is proposed to estimate the Bit Error Rate (BER) in a Wavelength Division Multiplexing (WDM) receiver with component crosstalk considering all possible bit combinations in the interfering channels instead of the usual worst-case approach. In addition, probability density function (pdf) and bit error rate (BER) with finite...

The present literature reports a study on the dynamics of a single loop optoelectronic oscillator. It has been observed that with the variation of the delay parameter the system depicts some complex behavior like limit cycle oscillation through Hopf bifurcation, chaotic oscillation.

In this paper, effects of alloy composition (x or y) on gain and bandwidth of Si/ Si1-xGex and Si/ Ge1-ySny heterostructure avalanche photodiodes (APDs) have been investigated. Photocurrent calculation in APD is based on the consideration of dead-space effect and carrier confinement at heterointerface. Impact ionization parameters of Si1-xGex and G...

We have investigated the effects of alloy composition (y) on gain of a Ge1−ySny heterostructure avalanche photodiodes (APDs). The band-offsets become a function of alloy composition and affect the carrier confinement at heterointerfaces. The photocurrent is computed using the composition dependent parameters and, hence, the effect of alloy composit...

We present a theoretical study of the gain of a CMOS compatible thin submicron Si-CMOS p-i-n avalanche photodetector (APD) suitable for high-speed, low-voltage operation. A 2-D model is used to estimate the avalanche build-up of carriers in the depleted region considering the dead-space effect. The model is also considered the effects of diffusion...

In this paper, oscillator strength and absorption cross-section of core-shell quantum dot (CSQD) with cubic geometry is computed for both normal and inverted structures. Intraband transitions between lowest three quantum states are considered to study optical properties along with the variation of structural parameters and incident radiation. Kane-...

A single loop optoelectronic oscillator is synchronized in the optical domain by an external microwave signal. The system equation of such an oscillator has been derived. Normalized output voltage and frequency are calculated and the steady state output voltage as a function of time is studied. Theoretical results are presented in this short commun...

Oscillator strength and absorption cross-section of core-shell triangular quantum wire is computed for intersubband optical transition between ground state and first excited state. Kane type band nonparabolicity of first order is considered to study the shift of cross-section peak with incident radiation, and also of the oscillator strength with st...

Metal-Semiconductor-Metal (MSM) photodetectors have ultra-low capacitance and are easily integrable with High Electron Mobility Transistor (HEMT) or Hetero Bipolar Transistor (HBT) preamplifiers for use in integrated photoreceivers at 1.55 μ m. In this paper, we calculate gain, overall bandwidth and sensitivity of both the combinations using the pr...

Eigenstates and intersubband transition energies of a T-shaped quantum wire embedded in square quantum wire are numerically computed by solving time-independent Schrodinger equation using finite difference technique. Dimensions of arm well and stem wells and material composition of shell layer is varied to observe the change in transition energies....

The present paper considers the influence of a variable center frequency tuned circuit replacing the narrowband RF filter in a conventional optoelectronic oscillator. The free-running amplitude and normalized frequency of such a system are derived and theoretical analysis coupled with experimental results showing good agreement are presented. Final...

An optoelectronic oscillator (OEO) under the influence of a weak interference has been investigated. The system equation of the OEO under the influence of interference has been derived. A novel technique for calculating the lock range of the oscillator using the harmonic balance method in presence of interference has been demonstrated. Theoretical...

In this paper, electron energies in core–shell quantum wires (CSQW) of rectangular, triangular, T-shaped, H-shaped and circular geometries are numerically computed by solving a time-independent Schrödinger equation using the finite difference technique. Computation is performed for both normal and inverted structures of CSQW, taking into account Ka...

In this paper, the influence of the In-band crosstalk-crosstalk beat noise on the Bit Error Rate (BER) of a preamplified WDM receiver is investigated assuming Gaussian approximation. From the analysis and comparison it is evident that in case of many interferers the crosstalk-crosstalk beat noise can significantly affect the value of BER and modify...

In future generation space based phased arrays and in pico-cellular broadband mobile communication systems operating at microwave frequencies optical techniques for transport and generation of electrical signals are widely used. In general, there are two main classes of optical transmitting and generating microwave frequencies: (1) methods using di...

Optical homodyne receivers based on modified Dither Optical Phase-Locked Loop is analyzed taking into account the laser phase noise, photo detectors shot noise and the dither signal. This modified loop contains all the components of a standard Dither OPLL in conjunction of an additional phase modulator. This modified loop considerably improves the...

The paper provides an analysis of different sizes red blood corpuscles (RBC) using surface Plasmon resonance (SPR) sensor. Change of RBC size affects the change of refractive index. SPR sensor is sensitive towards this small change of refractive index. A general formula is given in this paper such that just observing the output intensity of SPR sen...

Selective wavelength tuning of multiple quantum well based infrared photodetector is achieved by non-uniform doping distribution as well as dimensional variation in the structure. Result is obtained from the computation of the intersubband transition energy through self-consistent solution of the Poisson's and Schrödinger equations with appropriate...

Bandwidth calculation of Si1-yGey n+-i-p+ avalanche photodiode (APD) is described for multiplication layer down to tens of nanometers considering dead-space effect. In the analysis, the depletion region is discretized into equal energy segments to take into account the discontinuous nature of impact ionization in the multiplication layer due to dea...

Gain calculation of Si1-y
Gey
n+-i-p+ avalanche photodiode (APD) is described for multiplication layer down to tens of nanometers considering dead-space effect. Carrier diffusion from undepleted regions is considered to study the effect of low bias. The computed results are used to investigate the effect of Ge-composition (y) on the gain of a Si1-y...

In this paper, the electron energy and intersubband absorption coefficient are calculated for a spherical core shell quantum dot structure. Considering the variation of dot size over a layer and scattering mechanisms, Gaussian distribution in density of state is used in the analysis. Both the transition energy and the peak absorption coefficient de...

Component crosstalk causes severe system performance degradation in an optical network. In this paper the influence of the component crosstalk originated from signal-crosstalk beat noise, on the performance of a preamplified WDM receiver is investigated assuming both Gaussian and non-Gaussian model. From the analysis it is evident that for the fini...

In this paper, intersubband transition energy and oscillator strength of a semiconductor quantum disk are analytically computed by solving time-independent Schrödinger equation in presence of axial electric field. Results show that transition energy increases with increase of thickness but decreases with increasing radius. The external field alters...

The laser line-width required in PSK homodyne communication systems with Dither phase-locked loop receivers are exactly evaluated. It is shown that second-order phase-locked loops require at least 0.2 pW of signal power per every Hz of laser line-width (this number refers to the system with the detector responsivity 0.94 A/W, damping ratio 0.707, a...

Optical homodyne receivers based on modified balanced optical phase-locked loop is analyzed taking into account loop propagation delay. This modified loop contains all the components of a standard BOPLL in conjunction of an additional phase modulator. This modified loop offers a much improved tracking performance and also shows good improvements in...

In this paper, intersubband transition energy is computed for core-shell (normal and inverted) quantum dots (CSQD) of cubic and spherical geometries by solving. time-independent Schrodinger equation using finite-difference technique. Sparse, structured Hamiltonian matrices of order N-3 x N-3 for cubic and N x N for spherical dots are produced consi...

We describe the calculation of gain and bandwidth of an
n+-i-p+ avalanche photodiode (APD) for a
multiplication layer down to tens of nanometers. The computed results
are used to make a comparative study of gallium arsenide (GaAs) and
silicon (Si) APDs. In the analysis, the depletion region is discretized
into equal energy segments to take into acc...

In this paper, optimum detection threshold for minimum bit error rate (BER) due to four-wave mixing is calculated taking the probability distribution of power depletion as binomial and considering nonuniform channel spacing. Nondegenerate four-wave mixing has been assumed for the worst-case analysis. The effects of the number of interfering channel...

Optical interconnects hold the promise of revolutionizing computing speed having higher bandwidth and lower power consumption. For high packing density of optical interconnects, crosstalk is calculated considering the coupling of fields of two parallel identical neighboring waveguides. The study shows that there exists minimum pitch for a particula...

Energy eigenvalues of an inverted core–shell spherical quantum dot is numerically computed using finite difference technique, and corresponding intersubband transition energies are evaluated for the lowest three eigenstates. GaAs/AlxGa1−xAs material composition is considered for simulation purpose. Al mole fraction of the heterostrucutre is varied...

In this paper, performance of a Ge-on-Si Resonant-Cavity-Enhanced (RCE) Schottky Photodetector at 1.55_m has been investigated considering the effects of carrier confinements at the Si/Ge heterointerface. The transit-time delay and loss of carriers by recombination have been included in the model to calculate photocurrent, bandwidth, quantum effici...

A novel quantum wire laser structure is presented by designing inverted core-shell cylindrical quantum wire using AlxGa1-xAs/GaAs type-I heterostructure. The energy eigenvalues with corresponding density of states are numerically computed using finite difference technique. Intersubband transition energies are computed considering the lowest three e...

Energy eigenvalues for lowest three states and corresponding intersubband transition energies along with density of states of a core-shell cylindrical quantum wire is numerically computed using finite-difference technique (FDQ). Time-independent Schrödinger's equation is solved with appropriate boundary conditions, arises due to geometrical nature...

Energy eigenvalues and intersubband transition energies of a triangular quantum wire have been numerically computed by solving time-independent Schrödinger's equation with appropriate boundary conditions using finite difference technique for the lowest three eigenstates. Triangular wire is made of GaAs material, which is embedded in a rectangular w...