Malin Premaratne is an electrical engineer with diverse interests and physics, mathematics, bio-optics, and computer science skills. Malin’s main contributions are in theory, solution methods, computation, and pioneered many novel techniques, in theory, modelling and simulation of light generation (e.g., lasers and spasers) and light interaction with guided (e.g., optical fibre) and scattering media (e.g., biological tissue) and published over 250 journal papers (and additional over 100 conference papers), two books and four book chapters. Much contemporary scientific knowledge arises from modelling, and its importance is, if anything, growing. With the proliferation of high-performance computers, the current practice creates complex models and solves them numerically to study their behaviour.
Malin has spent one-third of his career in industry before joining academia. From 1998 to 2000, he was with the Photonics Research Laboratory, The University of Melbourne, where he was the Co-project Leader of the CRC Optical Amplifier Project and was also associated with Telstra, Australia, and Hewlett Packard, USA. From 2001 to 2003, Malin worked as a consultant to several companies, including Cisco, Lucent Technologies, Ericsson, Siemens, VPISystems, Telcordia Technologies, Ciena, and Tellium. Since 2004, he has guided the research program in high-performance computing applications to complex systems simulations at the Advanced Computing and Simulation Laboratory, Monash University, Clayton, where he holds many senior positions and is a Full Professor. He has visiting appointments with The University of California Los Angeles (UCLA), Jet Propulsion Laboratory at Caltech, Oxford University, The University of Melbourne, and Institute of Optics University of Rochester. Professor Premaratne is a Fellow, Optical Society of America (FOSA), a Fellow, Society of Photo-Optical Instrumentation Engineers(FSPIE) and a Fellow, Institute of Engineers Australia (FIEAust).
Publications (11)
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We present the polarization effect on surface plasmonic polariton (SPP) modes in plasmonic waveguides under high-intensity radiation via the Floquet engineering methods. First, we analyze the strong light coupling to the metallic system using a nonperturbative procedure. Then, we describe the behavior of dressed metal fermion system using the Floquet state solutions. Furthermore, we examine the impurity scattering effects on electron transport in disordered plasmonic metals using the generalized Floquet-Fermi golden rule. We also show that we can reduce the SPP propagation losses in plasmonic metals by applying a dressing field. We introduce a new figure of merit to compare the performance of popular plasmonic metals, assessing their performance enhancements under two different polarization types of dressing fields. Our study can be applied to accurately interpret the usage of strong external radiation as a tool in quantum plasmonic circuits and devices.
We present the band diagram analysis of a polaritonic crystal fabricated by periodically modulating the optical conductivity of a graphene sheet, which can be implemented as a virtual mirror in a Fabry-Perot type plasmonic resonator. The 2-Dimensional graphene sheet is supported by two dielectric media on top and the bottom and supports Surface Plasmon Polaritons (SPPs) at the interface. We use the Floquet-Bloch theory to write the fields in the periodically modulated structure. Using Maxwell's equations, we derive the relationship between the components of the SPP wavevector and the complex amplitude coefficients that define the linear relationship between the forward and backward propagating SPP modes. The set of nonlinear eigenvalue equations is then obtained by applying the boundary conditions at the interface. The non-retarded approximation is used to convert this to a linear eigenvalue problem. The dispersion relation is obtained by setting the determinant of the linear eigenvalue problem to zero. Band diagrams are obtained by varying the defining parameters of the Gaussian shaped periodic conductivity profile. The behaviour of the forbidden bands is then used to explain the behaviour of the SPP reflection profiles that have been observed in a recent work. The impact of the absorption losses introduced by the finite intrinsic electron relaxation time of graphene on the band structure is also analysed.
Excitations Energy transfer occurring among an excited donor chromophore and potential acceptor chromophores has gained prime research interest owing to the highly efficient nature of the energy transferring process. One of the more popular approximation methods in simulating this energy transfer is the multi-site exciton full polaron transformation-based quantum master equation which has shown the ability to interpolate between weak and strong system bath coupling regimes. It has been shown that decay processes in many physical processes follow the well-known exponential decay laws with inverse power law behaviour at longer time scales. Conventional ohmic-like spectral density functions, model this behaviour well. However, it has been shown quantum mechanically that the long-term relaxation of such systems also has a significant inverse logarithmic term that is not captured by ohmic-like SDF models. Therefore, logarithmic decays and logarithmic factors are not rare in the literature with respect to excitations energy transfer. Recently introduced Ohmic-like spectral density function that can account for slight perturbations in the frequency domain has used these logarithmic factors to model this perturbation. Our objective of this paper is to study the energy transfer of a multi-site exciton system attached to an environment where these logarithmic perturbations could be experienced, with a full polaron based quantum master equation. Our results reveal that, when system bath coupling strength is larger the derived multi-exciton full polaron transformation-based quantum master equation is unable to simulate accurate dynamics where in some scenarios the well-known phenomena of infrared divergence occur. On the other hand, when the system bath coupling strength is weak, derived equation conveys better results. In addition, results show that smaller Ohmicity values can suffer from acute distortions even for a smaller logarithmic perturbation. Also, we show that when logarithmic perturbations are increased, damping characteristics of the energy transfer are also increased in general.
Resonance energy transfer between an excited donor and a potential acceptor is a highly researched area in science. Multiple theories have been introduced in the literature to understand and simulate this energy transfer. The formulation of quantum master equation incorporating full polaron transformation approach is one of the approximation methods for simulating dynamics of the coherent resonance energy transfer. Full polaron based quantum master equation is well known for undergoing infrared divergence for Ohmic and sub-Ohmic environments where the spectral density function scales linearly or sub-linearly at low frequencies. Our objective of this paper is to study an environment where logarithmic perturbations can be experienced with a full polaron based quantum master equation and gauge its performance. In doing so, we study how a perturbation in the frequency domain affects the overall quantum coherence of the energy transfer. Our results demonstrate that for larger system bath coupling strengths, full polaron based quantum master equation is unable to provide accurate results whereas for weaker system bath coupling strengths, it performs better. Further, for a given system bath coupling strength, as logarithmic perturbations are increasing, the damping characteristics of the coherent energy transfer are also increasing. In addition, we show that smaller values of the Ohmicity parameter can suffer severe distortions even for a small logarithmic perturbation. Doing so, we show that full polaron transformation-based quantum master equation is capable of undergoing infrared divergence even for a super Ohmic environment, when higher orders logarithmic perturbations are present.
Forster Resonance Energy Transfer (FRET) is a major interparticle energy transfer mechanism used in a wide range of modern-day applications. Hence, enhancing the FRET rate by different mechanisms has been extensively studied in the literature. Obtaining Plasmonic enhanced FRET by placing a metal nanoparticle (MNP) in the vicinity of energy exchanging molecules is one such mechanism. Here we present a model to elucidate the effects of extraneous surface charges present on such a vicinal MNP on the FRET rate considering the nonlocal response of the MNP. This model is based on the well established extended Mie theory of Bohren and Hunt along with the idea of introducing an effective dielectric function for the charged MNP. Our results indicate that the excess surface charges will lead to a blueshift in the resonance frequency and greater enhancements in the FRET rate for both local and nonlocal response based methods. Furthermore, we propose potential substitutes for noble metals that are conventionally used in plasmonic enhanced FRET.
A noble metal nanoparticle (MNP)- quantum emitter (QE) composite nanostructure operates as a nanoscale counterpart of a conventional laser, and serves as an ultra-compact coherent source of surface plasmons, which holds the potential of bolstering device miniaturization. Equivalent to a standard laser, the MNP acts as the resonator, and the gain medium consists of pumped QEs. In this work, we demonstrate the possibility of engineering the emission statistics of such a plasmonic laser, to meet prerequisites set by its intended application. We perform a comprehensive analysis on plasmonic statistics of a spheroidal MNP-QE composite nanostructure, through reduced density matrix formalism, and examine the tunability of the key observable quantities against various system parameters including the geometry of the MNP, the rate of excitation, and the dielectric constant of the submerging medium, to gather the insights for customizing and optimizing this composite nanostructure for a particular application. For a given frequency of operation, our simulations offer a guide for the most suitable shape of the resonator, and provides the estimations for the expected energy output and its coherence, for a range of input power. Furthermore, it can be extended to assist in making the material choices. In essence, our work facilitates tailoring efficient, coherent and tunable plasmonic laser devices to power-up many promising nanoscale applications.
Spectral distribution of emission was measured in a large angular range (8 deg to 180 deg) around a self-assembled photonic crystal synthesized from colloids of Rhodamine-B dye-doped polystyrene. Its comparison with the emission from the same dye-doped colloids in a liquid suspension provides a better understanding of the anisotropic propagation of light within the structure due to its pseudo-gap properties. The spontaneous emission is suppressed by 40% in the presence of the stop band over a large bandwidth (∼50%) of the first-order bandgap in the ΓL direction, due to the appropriate choice of the colloidal diameter. Spectral shifts in the spontaneous emission spectrum occur with the variation in the detection angle. The inevitable disorder in the self-assembled crystals and the resultant effect on emission was modeled by comparing the experimentally obtained reflection spectrum with the band structure calculated using the Korringa-Kohn-Rostoker method to exclude finite-size effects. Reflection and transmission are complementary because of the absence of strong absorptive effects. The extent of redistribution in the emission from a photonic crystalline environment with respect to a homogeneous emitter is significant in the spectral and spatial domains.
We have previously demonstrated that Mie scattered statistically stationary partially coherent electromagnetic
fields result in spontaneous creation and nucleation of coherence vortices in the field both inside and outside the
scattering particle. In a succeeding study we showed that a regular lattice of coherence vortices can be generated
by illuminating a system of three scatterers with partially coherent light. In this paper, we analyze the field
scattered by differently arranged systems of scatterers and investigate the coherence variation of the scattered
field. We show that different patterns of coherence vortex networks can be realized depending on the spatial
arrangement of the scatterers. Different patterns of vortex networks generated in these scattering systems make
them suitable candidates for particle manipulation applications at microscopic levels.
The design and realization of chip-scale plasmonic devices have been considerably facilitated by computational
electromagnetic simulations and sophisticated nanofabrication techniques. For rapid device optimization, numerical
simulations should be supplemented by simple analytical expressions capable of providing a reasonable
estimate of the initial design parameters. In this paper, we develop an analytic approach and derive approximate
expressions for the transmittance of metal-dielectric-metal (MDM) waveguides coupled to single, double, and
periodic stub structures. Our method relies on the well-known analogy between MDM waveguides and microwave
transmission lines, and enables us to use standard analytical tools in transmission-line theory. The advantage of
our analytic approach over the previous studies is in accounting for the plasmon damping due to Ohmic losses
and reflection-induced phase shift at the stub end. We found that the analyzed waveguide configurations can
exhibit the characteristics of nanoscale filters and reflectors. We validate our analytical model by comparing
its predictions with numerical simulations for several MDM waveguides with different stub configurations. The
proposed theoretical results are particularly useful to reduce lengthy simulation times and will prove valuable in
designing and optimizing MDM-waveguide-based photonic devices.
We study the impact of Amplified Spontaneous Emission (ASE) noise on a Semiconductor Optical Amplifier (SOA)-based optical pulse delay discriminator and SOA-based distance ranger. Our experiments show that ASE reduces the sensitivity of these SOA-based devices and we confirm this finding by carrying out extensive simulations by modeling the ASE response of SOAs. The simulation results, obtained by numerical integration of these equations in MATLABTM using the NIMRODTM portal, are in qualitative agreement with experimental results.
Numerical models enable novel devices to be designed without the need for costly prototypes. Furthermore, internal variables, such as carrier density, are easily monitored, allowing a greater understanding of device operation to be gained. Recent advances in numerical techniques for the design and study of photonic devices, circuits systems are discussed. A comprehensive computer-aided design package for photonics is presented, and examples of photonic device, circuit and system simulation are shown.
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