Hossein Mosallaei · Northeastern University · PhdFit
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Hossein Mosallaei
Northeastern University · Electrical and Energy Engineering
Hossein Mosallaei is a Professor of Electrical and Computer Engineering at Northeastern University in the College of Engineering. He received his PhD from the University of California at Los Angeles (UCLA) in June 2001. He has held faculty positions at the University of Michigan's EECS Department as an Assistant Research Scientist from 2002 to 2005 before joining Northeastern University in 2005. He is the Director of the Metamaterials Laboratory at Northeastern and leads research activities in electromagnetics and optics, RF/optical metamaterials and metasurfaces, wireless antennas and sensors, microwave and millimeter-wave electronics, photonics and plasmonics, quantum optics and materials, and multiscale computation and AI. His research group is recognized for active and time-modulated photonics, and his work has been featured in prestigious journals. He is a Fellow of Optica, awarded in 2025, and has received numerous accolades for his contributions to the field.
Physical review. B./Physical review. B · 2025-03-26 · 5 citations
articleSenior author
Quantum emitters are fundamental to advancing technologies such as secure quantum communication, high-resolution imaging, and quantum computing by enabling on-demand single-photon generation. Precise control over the spectral and radiation characteristics of quantum emitters is crucial for optimizing quantum devices and integrated photonic systems. Nevertheless, traditional designs based on passive materials impose fixed functionality postfabrication, limiting the ability to tune spontaneous emission dynamically. This study introduces time-varying Mie resonators as a dynamic means to achieve real-time control over the spontaneous emission of a quantum source. A theoretical framework combining the time-Floquet method with multipole expansion is developed to model light-matter interactions in time-modulated environments. Our findings reveal that time modulation enables precise control over multipolar resonant modes, compensating for frequency detuning in the quantum emitter's radiation through an optimal feedback strategy. Moreover, we demonstrate that time modulation can facilitate directional control of far-field emission by selectively exciting specific multipoles and manipulating their mutual coupling. We further show that transverse Kerker conditions enhance radiation directionality and that time modulation can convert nonradiating anapole states into radiating modes via symmetry breaking. Our findings provide a comprehensive framework for real-time manipulation of quantum emitter radiation and open up possibilities for unique applications in integrated quantum physics.
Metamaterials exhibiting hyperbolic dispersion enable unprecedented control over light-matter interactions, from sub-diffraction imaging to enhanced spontaneous emission. However, conventional plasmonic hyperbolic metamaterials suffer from limited tunability and lack intrinsic emission capabilities, constraining their utility for active photonic devices. Here, we demonstrate the first room-temperature, electrically tunable, excitonic hyperbolic metamaterial using aligned films of chirality-pure semiconducting carbon nanotubes. Unlike plasmonic systems, these excitonic metamaterials of aligned nanotubes combine strong optical anisotropy with dynamic electrostatic tunability. Spectroscopic ellipsometry reveals that the hyperbolic dispersion window can be electrically shifted by 53 meV, enabling real-time switching between hyperbolic and elliptical regimes. Theory predicts that this tunability translates to the propagation angle being modulated by 34°, driven by a momentum enhancement 3.11 times that of free space, limited primarily by material losses that can be mitigated through improved alignment. In addition, simulations of the system exhibit a high Purcell factor of 1550 and a modulation of 37 % without an optical cavity for a dipole placed 5 nm above the aligned nanotubes. These findings establish excitonic carbon nanotubes as a versatile platform for dynamically reconfigurable photonic metamaterials, opening pathways for adaptive optical devices, electrically-controlled spontaneous emission, and tunable hyper-lenses operating at room temperature.
Janus micro- and nanoparticles, featuring unique dual-interface designs, are at the forefront of rapidly advancing fields such as optics, medicine, and chemistry. Accessible control over the position and orientation of Janus particles within a cluster is crucial for unlocking versatile applications, including targeted drug delivery, self-assembly, micro- and nanomotors, and asymmetric imaging. Nevertheless, precise mechanical manipulation of Janus particles remains a significant practical challenge across these fields. The current predominant methods, based on fluid flow, thermal gradients, or chemical reactions, have their precision and applicability limited by the properties of their background fluids. Therefore, this study proposes electrostatics to deliberately control the local orientation of optically asymmetric Janus particles (spherical and matchstick-like hybrid metal-dielectric objects) within a cluster to overcome the aforementioned restraints. We introduce a sophisticated multiphysics platform and employ it to explore and unveil the infrastructural physics behind the mechanical behavior of the particles when subjected to electrostatic stimuli in an ionic environment. We investigate how different deterministic and stochastic variables affect the particles' short- and long-term responses. By judicious engineering of amplitude, direction, and polarization of the external excitation, we demonstrate that the particles tend to undergo the desired rotational motion and converge to favorable orientations. The functionality of our approach is showcased in the context of an asymmetric imaging system based on optically asymmetric Janus particles. Our findings suggest a viable platform for adequate mechanical manipulation of Janus particles and pave the way for enabling numerous state-of-the-art applications in various fields.
We describe the requirements and associated technology development plan for the communications data link from low mass interstellar probes. This work is motivated by several proposed deep space and interstellar missions with an emphasis on the Breakthrough Starshot project. The Starshot project is an effort to send the first low mass interstellar probes to nearby star systems and transmit back scientific data acquired during system transit within the time scale of a human lifetime. The about 104-fold increase in distance to nearby stars compared to the outer planets of our solar system requires a new form of propulsion to reach speeds of approximately 20% of the speed of light. The proposed use of a low mass sailcraft places strong constraints on the mass and power for the Starshot communications system. We compare the communications systems in current and upcoming solar system probes, New Horizons and Psyche, against the requirements for Starshot and define Figures of Merit for the communications capability in terms of data downlink rate multiplied by distance squared per unit mass. We describe current and future technology developments required for the on-board transmitter (signal generation, signal distribution, and beamforming) and for the near-Earth communications receiver (low-cost large aperture telescopes, high resolution spectrometers, and single photon counting detectors). We also describe a roadmap for technology development to meet the goals for future interstellar communications.
Abstract The ability to manipulate the absorption, scattering, or reflectivity of light using synthetic materials has inspired innovations in nano‐ and micro‐materials for applications ranging from geoengineering to display optics. Asymmetric materials, like Janus particles, offer one solution to meet the needs of such technologies, as composition and geometry can be optimized to maximize directional optical properties in response to magnetic and/or electric fields, light, or electrostatic charge. In this work, a gram‐scale synthesis is applied to generate Janus matchstick particles comprising a gold head with a silica rod. Conditions are explored and optimized to elicit rotation of these matchstick particles under an alternating current (AC) electric field with varying field strength and frequency to maximize particle alignment. While only modest changes in transmission (≈8%) are observed over the visible spectral region with a bare silica rod, the application of an absorbing element increased transmission changes up to ≈23% demonstrating their utility as color‐changing materials. Experimental results are supported by theory and computation and highlight an important first step in activating directional optical effects in these materials which can be optimized for future adaptive technologies.
The advancement of imaging systems has significantly ameliorated various technologies, including Intelligence Surveillance Reconnaissance Systems and Guidance Systems, by enhancing target detection, recognition, identification, positioning, and tracking capabilities. These systems can be countered by deploying obscurants like smoke, dust, or fog to hinder visibility and communication. However, these counter-systems affect the visibility of both sides of the cloud. In this sense, this manuscript introduces a new concept of a smoke cloud composed of engineered Janus particles to conceal the target image on one side while providing clear vision from the other. The proposed method exploits the unique scattering properties of Janus particles, which selectively interact with photons from different directions to open up the possibility of asymmetric imaging. This approach employs a model that combines a genetic algorithm with Discrete Dipole Approximation to optimize the Janus particles' geometrical parameters for the desired scattering properties. Moreover, we propose a Monte Carlo-based approach to calculate the image formed as photons pass through the cloud, considering highly asymmetric particles, such as Janus particles. The effectiveness of the cloud in disguising a target is evaluated by calculating the Probability of Detection (PD) and the Probability of Identification (PID) based on the constructed image. The optimized Janus particles can produce a cloud where it is possible to identify a target more than 50% of the time from one side (PID > 50%) while the target is not detected more than 50% of the time from the other side (PD < 50%). The results demonstrate that the Janus particle-engineered smoke enables asymmetric imaging with simultaneous concealment from one side and clear visualization from the other. This research opens intriguing possibilities for modern obscurant design and imaging systems through highly asymmetric and inhomogeneous particles besides target detection and identification capabilities in challenging environments.
Advanced Photonics Research · 2023-05-10 · 9 citations
articleOpen accessSenior authorCorresponding
Orbital angular momentum and polarization states of highly focused vector vortex beams can be engineered to selectively excite the desired multipoles in nanoparticles, making them ideal candidates for complex optical applications. A platform based on the generalized Lorenz–Mie theory integrated with the complex source point method is developed to model the interaction of such beams with particles analytically. The existing platform is extended for obtaining the full‐vector electromagnetic fields, outlining the observed effects that adding a substrate brings to the problem space. Despite the cross‐coupling between different multipoles induced by the substrate, it is concluded that the proper choice of beam parameters enables the selective excitation of multipoles even in the critical case of a plasmonic substrate. The proposed formalism is general and allows a multipole study of the optical forces. Selective excitation is exploited to control the imparted optical forces on particles placed on a plasmonic substrate. 3D trapping regions are achievable for highly absorptive and high‐refractive‐index particles. Motion trajectory analyses are performed to demonstrate the trapping stability, concluding that highly focused optical beams, owing to the exceptional selective excitation ability, are suitable candidates for novel optical manipulation applications.
Advanced Photonics Research · 2023-01-31 · 7 citations
articleOpen accessSenior authorCorresponding
While optical pulse shapers have important applications in classical and quantum communication regimes and laser resonant cavities, engineering of group delay dispersion (GDD) remains one of their greatest challenges. Herein, by taking advantage of the electrically tunable optical properties of 2D material and the low‐loss nature of dielectric material. This paper demonstrates how an active tunable all‐dielectric metasurface assisted by 2D material can be leveraged to shape the temporal profile of a pulse. The proposed metasurface consists of an array of nanobars covered by a 2D sheet and positioned on a distributed Bragg reflector (DBR) as a perfect mirror to design a phase‐only modulator. Upon introducing in‐plane asymmetries, the quasi‐bound state in the continuum (QBIC) resonance emerges under normal incidence, which subsequently leads to achieving both significant GDD and the two regimes of pulse stretching and compressing via boosting the effect of the permittivity variation of molybdenum disulfide (MoS 2 ). The monolayer MoS 2 proves to be an excellent substitute for other tunable materials with inherent dissipative loss in the visible frequency range. Following such an active tunable geometrically fixed configuration, various pulse‐shaping operations are achieved, including compression (peak intensity up to 350%), expansion (peak intensity from 60%), splitting, and higher‐order distortion.
Space-time metasurfaces are great candidates for breaking the Lorentz reciprocity thorough inducing the desired momentum for photonic transitions between two modes. However, the significant difference between the carrier and modulation frequencies in photonic metasurfaces leads to negligible spatial pathway variation of light at different sidebands and weak power isolation. To surmount this obstacle, herein the design principle of the high Q-factor space-time metasurface is demonstrated that increases the lifetime of photons such that the optical cycle becomes comparable with the modulation cycle and strong power isolation is maintained by lifting the adiabaticity of modulation. It is shown that under time-reversal and by the virtue of modulation induced phase shift strong free space power isolation of ≈35dB is achieved between the two arbitrary ports at near-infrared regime.
Advanced Theory and Simulations · 2023-10-10 · 5 citations
articleOpen accessSenior authorCorresponding
Abstract The non‐rigidity of the nanophotonic metasail platform and the intense imparted optical force from the terrestrial laser source lead to deformations during the propulsion stage. These deformations must be taken into consideration due to their potential adverse impact on communication performance. Alterations in the shape of the sail body result in varying angles of incidence and polarization components observed by the photonic unit cell, significantly impacting their intended performance. Based on this premise, this paper proposes utilizing a reflective all‐dielectric, low‐power active metasurface that dynamically compensates for the effects of deformation and facilitates beam‐steering for communication purposes among different light sails in interstellar space. Configured as p‐n multi‐junction layers, the constituent elements of the metasurface enable modulation of carrier concentrations through multigate biasing. Through electrostatic simulations, it demonstrates that the required permittivity modulation of can achieve a wide phase span of 320°. Furthermore, it has investigated the effect of the presence of non‐functional portions in the far‐field radiation pattern of the light sail and highlighted the critical role of tunable elements in mitigating its impact. The obtained results hold great promise for realizing successful interstellar downlink communication between such gram‐scale nano‐crafts and Earth.
