About

Professor Mercedeh Khajavikhan joined the faculty of the University of Southern California in the Ming Hsieh Department of Electrical Engineering, Viterbi College of Engineering, in August 2019 as an Associate Professor and was promoted to full professor rank in January 2022. She also holds a joint appointment at the Department of Physics & Astronomy, Dornsife College of Letters, Arts, & Sciences at USC. She received her Ph.D. in Electrical Engineering from the University of Minnesota in 2009. After completing her doctorate, she worked as a postdoctoral researcher at the University of California in San Diego, focusing on the design and development of nanolasers, plasmonic devices, and silicon photonics components. In August 2012, she began her career as an Assistant Professor at the College of Optics and Photonics (CREOL) at the University of Central Florida, where she primarily worked on unraveling novel phenomena in active photonic systems. Professor Khajavikhan's research centers on optics and photonics, with a particular emphasis on active photonic systems and nanophotonic devices. She has been recognized with several prestigious awards, including the NSF Early CAREER Award in 2015, the ONR Young Investigator Award in 2016, the DARPA Young Faculty Award in 2018, the University of Central Florida Reach for the Stars Award in 2017, the UCF Luminary Award in 2018, and the DARPA Director's Fellowship in 2020. She is a fellow of Optica (formerly the Optical Society of America) and the American Physical Society.

Research topics

• Quantum mechanics
• Theoretical physics
• Physics
• Mathematics
• Classical mechanics

Selected publications

• Chern topological lasing via gain modulation

  Physical review. B./Physical review. B · 2026-01-20

  article
  PublisherDOI

• Localized dynamic lensing with instantaneous extended depth of field via collinear light–sound interactions

  Med-X · 2026-01-06

  articleOpen accessSenior author

  Abstract Tunable acousto-optic (AO) lenses have recently emerged as versatile tools for optical beam shaping, imaging, and particle manipulation. Conventional AO lenses rely on light propagating orthogonally to a standing ultrasonic field, producing Bessel-like beam patterns via the Raman–Nath effect that compromise focal localization and depth of field (DoF). Here, we introduce a novel class of AO lenses based on a three-dimensional, dynamically variable refractive index profile generated by a z-axis-scanning focused ultrasound transducer. By exploiting co- and counter-propagating light–sound interactions over an extended axial range, we achieve fully controllable, localized optical focusing with an instantaneous extended DoF. We demonstrate dynamic tuning of focal position, lateral resolution, and optical power throughput by adjusting ultrasound parameters. This approach offers a promising platform for applications requiring precise remote focusing, three-dimensional micromanipulation, and deep tissue imaging or therapy. Graphical Abstract

  PublisherOA PDFDOI

• Author Correction: Universal routing of light via optical thermodynamics

  Nature Photonics · 2026-05-05

  articleSenior author
  PublisherDOI

• Observation of low-temperature ground state purification via optical thermodynamics

  2025-01-01

  articleSenior author

  Conservation of probability density in a linear, passive system prohibits the transformation of an incoherent ensemble into a coherent one. Utilizing optical thermodynamics, we study the conditions for condensation into a coherent ground state.

  PublisherDOI

• Observation of Joule–Thomson photon-gas expansion

  Nature Physics · 2025-01-14 · 8 citations

  articleOpen access
  PublisherOA PDFDOI

• Fundamental mode excitation via Joule–Thomson light expansion in nonlinear optical lattices

  Optics Letters · 2025-01-22 · 1 citations

  articleOpen access

  Under linear conditions, power injected from a single waveguide into a multi-core fiber array results in multimode propagation, progressively diminishing the spatial coherence of light. In this work, we introduce a comprehensive approach to mitigate this coherence loss by means of a nonlinear thermodynamic Joule-Thomson expansion. By leveraging the tools of optical thermodynamics, we demonstrate that as light undergoes a sudden transition from a small to a larger nonlinear optical array, it can abruptly drop its optical temperature to near-zero values. During this cooling process, light irreversibly flows into the system's fundamental mode with very high efficiency, synchronizing all elements of the lattice with the input port. We show that this nonlinear effect is highly predictable even in systems of arbitrary geometry and shape and can be controlled precisely by the initial conditions at the input of the array. In particular, for a single injection point, the reduction in optical temperature can be directly determined by the total power, irrespective of the input location.

  PublisherDOI

• Photon-photon chemical thermodynamics of frequency conversion processes in highly multimode systems

  2025-01-01

  article

  We present a comprehensive stoichiometric theory capable of predicting and optimizing the conversion efficiencies of frequency generation processes within highly complex nonlinear multimode waveguide systems. Pertinent examples are provided.

  PublisherDOI

• Nonlinear Topological Photonics: Capturing Nonlinear Dynamics and Optical Thermodynamics

  ACS Photonics · 2025-04-29

  reviewOpen access

  Combining multiple optical resonators or engineering dispersion of complex media has provided an effective method for demonstrating topological physics controlling photons in unprecedented ways such as unidirectional light propagation and spatially localized modes between an interface or on a corner. Further, adding nonlinear responses to those topological photonic systems has enabled achieving diverse phases of photons in both space and time, allowing for more functionalities in photonic devices that provide a new playground for studying dynamic features of nonlinear topological systems. However, most methods for describing nonlinear topological photonic systems rely on linear topological theories, making it challenging to accurately characterize the topology of nonlinear systems. Thus, substantial efforts have focused on rigorously describing nonlinear topological phases and developing effective tools to analyze nonlinear topological effects. Meanwhile, coupled multimode optical waveguides with nonlinear dynamic responses provide an excellent platform for the statistical description of photons, opening a new paradigm called "optical thermodynamics". This review will introduce the basic concepts of nonlinear topological photonics and the recent development of theoretical approaches focusing on data-driven approaches for creating phase diagrams as well as the spectral localizer framework and the pseudospectrum method for understanding optical nonlinearities in topological systems. In addition, the new concept of optical thermodynamics will be introduced with some recent theoretical works.

  PublisherDOI

• Selective filtering of photonic quantum entanglement via anti–parity-time symmetry

  Science · 2025-03-27 · 18 citations

  articleOpen accessSenior authorCorresponding

  Entanglement is a key resource for quantum computing, sensing, and communication, but it is susceptible to decoherence. To address this, research in quantum optics has explored filtering techniques such as photon ancillas and Rydberg atom blockade to restore entangled states. We introduce an approach to entanglement retrieval that exploits the features of non-Hermitian systems. By designing an anti-parity-time two-state guiding configuration, we demonstrate efficient extraction of entanglement from any input state. This filter is implemented on a lossless waveguide network and achieves near-unity fidelity under single- and two-photon excitation and is scalable to higher photon levels, remaining robust against decoherence during propagation. Our results offer an approach to using non-Hermitian symmetries to address central challenges in quantum technologies.

  PublisherOA PDFDOI

• Photon–photon chemical thermodynamics of frequency conversion processes in highly multimode systems

  Light Science & Applications · 2025-05-12 · 2 citations

  articleOpen access

  Frequency generation in highly multimode nonlinear optical systems is inherently a complex process, giving rise to an exceedingly convoluted landscape of evolution dynamics. While predicting and controlling the global conversion efficiencies in such nonlinear environments has long been considered impossible, here, we formally address this challenge even in scenarios involving a very large number of spatial modes. By utilizing fundamental notions from optical statistical mechanics, we develop a universal theoretical framework that effectively treats all frequency components as chemical reactants/products, capable of undergoing optical thermodynamic reactions facilitated by a variety of multi-wave mixing effects. These photon-photon reactions are governed by conservation laws that directly determine the optical temperatures and chemical potentials of the ensued chemical equilibria for each frequency species. In this context, we develop a comprehensive stoichiometric model and formally derive an expression that relates the chemical potentials to the optical stoichiometric coefficients, in a manner akin to atomic/molecular chemical reactions. This advancement unlocks new predictive capabilities that can facilitate the optimization of frequency generation in highly multimode photonic arrangements, surpassing the limitations of conventional schemes that rely exclusively on nonlinear optical dynamics. Notably, we identify a universal regime of Rayleigh-Jeans thermalization where an optical reaction at near-zero optical temperatures can promote the complete and entropically irreversible conversion of light to the fundamental mode at a target frequency. Our theoretical results are corroborated by numerical simulations in settings where second-harmonic generation, sum-frequency generation and four-wave mixing processes can manifest.

  PublisherOA PDFDOI

Recent grants

• EAGER: Fundamental Considerations in Using Non-Hermitian Microscale Resonant Optical Structures for Rotation Sensing

  NSF · $48k · 2019–2021

• CAREER: Novel Photonic Structures Using Non-Hermitian Exceptional Points

  NSF · $291k · 2019–2021

• CAREER: Novel Photonic Structures Using Non-Hermitian Exceptional Points

  NSF · $500k · 2015–2019

• EAGER: Fundamental Considerations in Using Non-Hermitian Microscale Resonant Optical Structures for Rotation Sensing

  NSF · $200k · 2017–2020

Frequent coauthors

• Demetrios N. Christodoulides

  University of Central Florida

  192 shared

• William E. Hayenga

  72 shared

• Midya Parto

  56 shared

• Paweł S. Jung

  51 shared

• Hossein Hodaei

  Institute of Electrical and Electronics Engineers

  51 shared

• Absar U. Hassan

  46 shared

• Fan O. Wu

  Fuzhou University

  40 shared

• Georgios G. Pyrialakos

  University of Southern California

  35 shared

Labs

• Khajavikhan Optics and Photonics GroupPI

Education

• Ph.D., Electrical Engineering

  University of Southern California

  2010

• M.S., Electrical Engineering

  University of Southern California

  2006

• B.S., Electrical Engineering

  Sharif University of Technology

  2004

Awards & honors

• NSF Early CAREER Award (2015)
• ONR Young Investigator Award (2016)
• DARPA Young Faculty Award (2018)
• University of Central Florida Reach for the Stars Award (201…
• UCF Luminary Award (2018)