Arti Agrawal

University of Technology Sydney | UTS

Over the years, photonic components have grown in both complexity and function. Photonic device architectures have dimensions that are much smaller than the wavelength of operation, and employ dense integration, along with the use of novel 2D materials and physical effects to control optical properties and light-matter interaction. These developmen...

In this paper, we propose a theoretical laser model to analyse nanowire lasers with quantum-disks embedded inside them as the gain medium. Our laser model enables us to separately investigate the impact of the key parameters such as Purcell factor on the threshold and the height of the kink. Results and discussion we use our laser model to simulate...

In this paper, we present a numerical estimation of spontaneous emission factor for nanowire lasers and, investigate the impact of Purcell effect F and spontaneous emission factor β on the threshold and the L-L curves. Theoretical calculations provide more insights into the laser behaviour as they predict spontaneous emission coupling efficiency be...

This paper presents a numerical approach to estimating the spontaneous emission coupling efficiency in semiconductor lasers with lower-dimension gain mediums. Also, the impact of the Purcell effect F and spontaneous emission factor β on the threshold and the height of the kink in the L-L curves is studied. Our theoretical calculations provide more...

The mid-infrared (MIR) is an exciting spectral range that also hosts useful molecular vibrational fingerprints. There is a growing interest in nanophotonics operating in this spectral range, and recent advances in plasmonic research are aimed at enhancing MIR infrared nanophotonics. In particular, the design of hybrid plasmonic metasurfaces has eme...

The ability to control the interaction of light and matter at the nanoscale is at the heart of the field of nanophotonics. This subdiffractional confinement of light can be achieved through the stimulation of surface polaritons, most notably surface plasmon polaritons (SPPs). However, the high optical losses and lack of tunability of conventional p...

This work presents the design and optimization of a cascade nano-laser using CH3NH3PbI3 perovskite. Due to increasing threshold gain with decreasing device size and high Auger losses, the use of perovskite as the active medium in the cascade nano-laser was proposed, as the material possesses a high emission rate in the visible wavelength region, wi...

Plasmonic nanohole arrays has attracted tremendous attention in biosensing applications because of the flexibility in the optical signature design, high multiplexing capabilities, simple optical alignment setup, and high sensitivity. The quality of the metal film, including metal crystallinity and surface roughness plays an important role for deter...

The mid-infrared optical spectrum hosts a variety of promising photonic applications. Herein we simulate and experimentally demonstrate reflectance enhancement of MIR light using graphene-coated silicon carbide nanowires on silicon, showing promise for on-chip MIR nanophotonics.

Knowledge of the distribution of the aspect ratios (ARs) in a chemically-synthesized colloidal solution of Gold Nano Rods (GNRs) is an important measure in determining the quality of synthesis, and consequently the performance of the GNRs generated for various applications. In this work, an algorithm has been developed based on the Bellman Principl...

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A rapid and ubiquitous method to characterize samples of chemically synthesized Gold Nano Rods (GNRs) is by measuring their UV-visible spectra. The presence of transverse and longitudinal surface plasmon resonance peaks in UV-visible spectra indicate the presence of GNRs. However, the quality of the synthesised sample, and thus their performance in...

This article presents four different plasmonic structures using Graphene which yielded an efficient plasmonic mode with low loss for Supercontinuum(SC) generation. At an operating wavelength of 1550 nm in these structures, we generated a multi-octave broadband SC spectrum ranging from 1.5 um–25 um at a low input peak power of 1 W. Due to pumping in...

Time domain analysis of electromagnetics is currently dominated by the finite difference time domain (FDTD) method. Current finite element (FE) counterparts of the FDTD method are slower in execution and hard to parallelise. This chapter presents a point matched finite element based method with dual perforated mesh system which allows faster execut...

This book brings together the recent cutting-edge work on computational methods in photonics and their applications. The latest advances in techniques such as the Discontinuous Galerkin Time Domain method, Finite Element Time Domain method, Finite Difference Time Domain method as well as their applications are presented. Key aspects such as modelli...

A good texturing pattern for solar cells needs to combine low Reflectance over a large wavelength range and low surface recombination to maximize the output. Nanowire and pyramid patterns offer low Reflectance in the longer and shorter wavelength regions respectively. This paper introduces an exciting new “hut” like texturing pattern with excellent...

This paper introduces an exciting new hut-like texturing pattern that shows lower Reflectance than pyramids and nanowires in the shorter and longer wavelengths respectively.

We demonstrate numerically that the use of dispersion-engineered microstrucured fibers made with chalcogenide glasses allows one to generate ultrabroadband supercontinuum spectra in the mid-infrared region by launching optical pulses at a suitable wavelength. As a specific example, numerical simulations show that such a 1 cm long fiber, made with G...

In this paper, we present the simulation results of a hut-like array of micro pillars pattern for silicon solar cells. The Reflectance reduces when increasing the angle between substrate and base of the micro pillars.

Arti Agrawal says that more needs to be done to address the gender gap in science.

Arrays of vertical silicon micropillar radial junction solar cells have been fabricated by diffusion of direct application spin on dopant and from the vapour phase through proximity rapid thermal diffusion. The micropillars were fabricated by optical lithography and deep reactive ion etching. The micropillar arrays show superior antireflective prop...

In this paper, we report the optical properties of a Silicon (Si) solar cell when varying the configuration (hexagonal and square) of a micro pillar array on the cell surface using the FDTD technique . It was found that the hexagonal configuration gives better performance.

Efficient ways of enhancing l ight trapping in thin film solar cells is of great importance for the solar cell industry. A set of techniques used to trap the light is to texture the solar cell surface. In this research we study the impact on the optical absorption of a Si solar cell by placing micro pillars on the cell surface. A rigorous analysis...

Students from England have recently been hit by steep rises in tuition fees. Arti Agrawal asks whether the decision to do so – based on free-market economics – was right.

In this paper, we report the optical properties of a silicon (Si) solar cell when varying the parameters of a micro pillar array on the cell surface using the FDTD technique.

In this paper, we report the optical properties of a silicon (Si) solar cell when varying the parameters of a micro pillar array on the cell surface using the FDTD technique.

Simulations are presented of a very broad and flat supercontinuum (SC) in both the normal and anomalous group velocity dispersion regimes of the same equiangular spiral photonic crystal fiber at low pumping powers. For a pump wavelength at 1557 nm and average pump power of 11.2 mW, we obtained a bandwidth >3 μm (970 nm–4100 nm) at 40 dB below the p...

We present an algorithm that adapts the mature stack and draw (SaD) methodology for fabricating the exotic equiangular spiral photonic crystal fiber (ES-PCF). The principle of Steiner chains and circle packing is exploited to obtain a nonhexagonal design using a stacking procedure based on hexagonal close packing. The optical properties of the prop...

Time domain analysis of electromagnetic wave propagation is required for design and characterization of many optical and microwave devices. The FDTD method is one of the most widely used time domain methods for analysing electromagnetic scattering and radiation problems. However, due to the use of the Finite Difference grid, this method suffers fro...

The full-vectorial H and E-field profiles along with the Poynting vector are shown for the nanoscale silicon waveguides, which are the basic components of compact silicon photonic devices and systems.

A rigorous modal solution approach, based on the numerically efficient finite-element method (FEM), has been used to design and characterize a photonic crystal fiber (PCF) with a porous air core, which has the potential for use for low-loss guidance of terahertz (THz) waves. Here, for the first time, it is reported that a large fraction of the powe...

We propose a novel Archimedean spiral PCF design for residual dispersion compensation. The proposed fiber can be fabricated using sheet rolling techniques, and shows D ~ -149ps/nm/km in the range (1.3-1.7μm).

An Equiangular Spiral Photonic Crystal Fiber (ES-PCF) design in Topas (R) R for use in the Terahertz regime is presented. The design shows ultra low bending loss and very low confinement loss compared to conventional Hexagonal PCF (H-PCF). The ES-PCF has excellent modal confinement properties, together with several parameters to allow the optimizat...

We present a full-vectorial modal analysis of a segmented cladding fiber (SCF). The analysis is based on the H -field vectorial finite element method (VFEM) employing polar mesh geometry. Using this method, we have analyzed the circular SCF and the elliptical SCF. We have found that the birefringence of the circular SCF is very small ( 1.0 × 10 − 8...

A rigorous modal solution approach based on the numerically efficient finite element method (FEM) has been used to design a tapered photonic crystal fiber with a large mode area that could be efficiently coupled to an optical fiber. Here, for the first time, we report that the expanded mode area can be stabilized against possible fabrication tolera...

In this paper, the accurate and numerically efficient finite element (FE)-based beam propagation method (BPM) has been employed to investigate second harmonic generation (SHG) in highly nonlinear soft glass (SF57) equiangular spiral photonic crystal fibers (ES-PCFs) for the first time. It is shown here that the SHG output power in highly nonlinear...

In this work, it is shown that the differential loss between the TE- and TM-polarized fundamental modes in a highly birefringent photonic crystal fiber (PCF) can be enhanced by bending the fiber. As a result, a design approach for single-mode single-polarization operation has been developed and is discussed. A rigorous full-vectorial H-field-based...

Design and analysis of various photonic crystal fibers are reported, particularly for their single-mode single-polarization operation, dispersion control and nonlinear applications by using full-vectorial finite element simulations.

The evolution of surface plasmon (SP) supermodes through the effective coupling of isolated SP modes in a semiin- sulating quantum cascade laser (QCL) waveguide is thoroughly discussed here. The effect of varying the material and geometric parameters of GaSb/AlGaSb QCL operating at 3.0 THz are thor- oughly studied using a full-vectorial finite-elem...

We demonstrate very low and flat dispersion (±2ps/nm/km, slope<;0.0028ps/nm²/km@1.8-2μm) in the Mid-Infrared band along with high non-linear coefficient (γ=1155W^-1km^-1@1.93μm) achieved in a tellurite photonic crystal fiber for generating supercontinuum with a broad bandwidth.

We present results for a broadband supercontinuum spanning almost two octaves (575 nm - 1600 nm) generated in an equiangular spiral photonic crystal fiber proposed earlier. The pump source is taken to be Yb - doped fiber laser at 1.06 mum. The fiber has two zero dispersion wavelength (at 885 nm and 1115 nm) with very high nonlinearity ( >5580 W-1 k...

The full-vectorial H and E-field profiles along with the Poynting vector are shown for the nanoscale silicon waveguides. Uses for sensing and polarization conversion are also discussed for the design of compact silicon photonic devices.

A finite element based time domain method is proposed to solve the Maxwell’s curl equations. This technique can handle irregular mesh. The method also utilises less node to store all field components.

An elliptical air-hole golden spiral photonic crystal fiber (EGS-PCF) is analyzed with the full-vectorial finite element method. The air-holes in the EGS-PCF are arranged in a spiral pattern governed by the Golden Ratio, where the design has been inspired by the optimal arrangement of seeds found in nature. The EGS-PCF exhibits extremely high biref...

We have carried out a rigorous H-field-based full-vectorial modal analysis and used it to characterize, more accurately, the abrupt dielectric discontinuity of a high index contrast optical waveguide. The full-vectorial H and E fields and the Poynting vector profiles are described in detail. It has been shown through this work that the mode profile...

A modal solution approach based on a rigorous full vectorial finite element method has been used to determine single mode single polarization properties of a bent highly birefringent fiber photonic crystal fiber. A design approach for the single mode single polarization design has been discussed.

The high index contrast of silicon waveguide allows light confinement in submicron size waveguides along with very compact bends, to allow increased functionality of photonic integrated circuits. A rigorous H-field based full-vectorial modal analysis has been carried out, which is used more accurately to characterize the abrupt dielectric discontin...

An equiangular spiral photonic crystal fiber (ES-PCF) design in soft glass is presented that has high nonlinearity ( gamma > 5250 W^-1 middot km^-1 at 1064 nm and gamma > 2150 W^-1 middot km^-1 at 1550 nm) with a low and flat dispersion (D ~ 0.8 ps/kmmiddotnm and dispersion slope ~ -0.7 ps/km middot nm<sup>2<...

The development of highly dispersive lower and higher order cladding modes and their degeneration with respect to the fundamental core mode in a bent photonic crystal fiber is rigorously studied by use of the full-vectorial finite element method. It is shown that changes in the bending radius can modify the modal properties of large-area photonic c...

Terahertz quantum cascade laser waveguides were characterized using the vector finite element method. Waveguides based on GaSb/AlGaSb multiple quantum well structures were simulated, for which detailed mode profiles, power confinement and loss factors are shown.

Modal solutions for metal-coated defect-core photonic crystal fiber (PCF) with a central air-hole have been obtained by using a full-vectorial finite element method to model the guidance of THz waves. It has been shown that the surface plasmon modes can couple with the defect-core PCF mode to form supermodes, with potential for sensing applications...

A rigorous finite element analysis on a new Teflon PCF with metal coated central air-hole shows the formation a Surface Plasmon assisted fundamental mode with controllable modal properties for THz sensing application.

A soft-glass spiral PCF design is analysed using the FEM approach showing gamma >2000 W-1km-1 at 1550 nm and 4000 W-1km-1 (1064 nm). The design exhibits low, flat anomalous dispersion (~15 ps/nm.km and dispersion slope~0.25 ps/nm2.km) at 1064 nm.

A golden spiral photonic crystal fiber (GS-PCF) design is presented in which air holes are arranged in a spiral pattern governed by the golden ratio, where the design has been inspired by the optimal arrangement of seeds found in nature. The birefringence and polarization properties of this fiber are analyzed using a vectorial finite-element method...

A modal solution approach based on the powerful, finite element method (FEM) using a full-vectorial H-field formulation has been used to determine the single-mode operation of a photonic crystal fiber (PCF). The modal solution of the fundamental space-filling mode has also been obtained to identify the cutoff conditions of the waveguide modes. The...

A finite element based full-vectorial modal solution approach has been developed to identify single mode operation of Teflon photonic crystal fibers and to characterize their modal and bending losses in the THz frequencies.

A novel quasi crystal spiral design for a Photonic Crystal Fiber is optimized by the Finite Element method. The fiber dispersion can be designed to have large negative values by tuning the design parameters.

Modal solutions for Photonic Crystal with circular and square shaped rods have been obtained using the Finite Element method. We compare the field distributions and effective indices with rod shape in the Photonic Crystal. We optimize sharp 90° bends with different rod shape using a Finite Element Time Domain method.

A modal solution approach, based on a powerful, full-vectorial, H-field based finite element method (FEM), has been used to analyze the single mode operation of a PCF and the modal solution of the fundamental space filling mode has been analyzed. The FEM with perfectly matched layer condition has been used to characterize the leakage loss of a PCF...

Modal solutions for Photonic Crystal with circular and square shaped rods have been obtained using the Finite Element method. We compare the field distributions and effective indices with rod shape in the Photonic Crystal.

We describe a method for analytical computation, including the square-root operation, of the propagation matrix used in the finite-difference split-step non-paraxial method thereby reducing the computation time significantly.

A novel split-step finite-difference method for wide-angle beam propagation is presented. The formulation allows solution of the second-order scalar wave equation without having to make the slowly varying envelope and one-way propagation approximations. The method is highly accurate and numerically efficient requiring only simple matrix multiplicat...

Modal properties of silica waveguides are presented along with their results on single mode operation, spot-size variations, confinement factor and, modal field profiles for different index contrast value between the core and the claddings. Both dominat and non-dominat field profiles and their transverse variations are also shown. Numerically simul...

A method based on symmetrized splitting of the propagation operator in the finite difference scheme for non-paraxial beam propagation is presented. The formulation allows the solution of the second order scalar wave equation without having to make the slowly varying envelope and one-way propagation approximations. The method is highly accurate and...

We present a performance comparison of wide-angle beam propagation methods presented in the recent past. We show that non-iterative, fast and accurate formulations, especially based on collocation method score over the conventional Pade based methods.

The perfectly matched layer (PML) boundary condition is generally employed to prevent spurious reflections from numerical boundaries in wave propagation methods. However, PML requires additional computational resources. We have examined the performance of the PML by changing the distribution of sampling points and the PML’s absorption profile with...

A new method for solving the wave equation is presented that is nonparaxial and can be applied to wide-angle beam propagation. It shows very good stability characteristics in the sense that relatively larger step sizes can be taken. An implementation by use of the collocation method is presented in which only simple matrix multiplications are invol...

A new method for solving the wave equation is presented, which, being non-paraxial, is applicable to wide-angle beam propagation. It shows very good stability characteristics in the sense that relatively larger step-sizes can be used. It is both faster and easier to implement. The method is based on symmetrized splitting of operators, one represent...

In numerical wave propagation methods, the perfectly matched layer (PML) boundary condition is employed to prevent spurious reflections. However, PML takes additional resources in number of computation points and time. In this study, the PML performance is examined with change in the distribution of sampling points and PML absorption profile with a...

A method, based on the collocation method, for wide angle and bi-directional propagation of non-paraxial waves is presented. The second-order wave equation is converted to a matrix ordinary differential equation, which is solved numerically requiring no correction for energy conservation or evanescent mode suppression. No approximation for the wave...

The photonic crystal fiber (PCF), which is also known as holey fiber, is a micro-structured fiber, where arrays of holes running along the waveguide length, has more controllable fabrication parameters than standard single mode fiber. Increasing interest is being shown in such PCFs for a range of applications in optical communications, sensing and...

Numerical methods for beam propagation are widely used for design and analysis of waveguides and devices. These methods directly give the total picture of the field as it propagates through a waveguide, which may have a very complicated structure involving several branches and variations in physical characteristics. Conventional methods are based o...

The design and characterization of a novel surface plasmon-assisted defect-core photonic crystal fiber in Teflon, with a metal-coated central air-hole is reported using a rigorous full-vectorial finite element method. It has been shown that the dielectric mode can be coupled to the surface plasmon mode resulting in an enhanced power distribution in...

We analyze an elliptical core segmented cladding fibre using the vector finite element method (FEM) and show that the segmented cladding can effectively control the birefringence of the fibre. The analysis should be useful for fibre-based polarization controlling devices and single-polarization devices.