About

Anna Swan is an Affiliate Faculty and Associate Professor in the Department of Electrical and Computer Engineering at Boston University. Her research focuses on high spatial resolution spectroscopy, including spectral self-interference techniques to enhance fluorescence microscopy resolution, resonant Raman studies of single carbon nanotubes, and high spatial resolution stress measurements in micro-electromechanical systems (MEMS) using micro-Raman spectroscopy. She also investigates the optical properties of low-dimensional systems such as carbon nanotubes and graphene, as well as biological imaging and detection using interference techniques like 4Pi microscopy and spectral fluorescence microscopy. Dr. Swan holds a Ph.D. in Physics from Boston University and an M.D. in Physics Engineering from Chalmers University in Gothenburg, Sweden.

Research topics

• Materials science
• Optoelectronics
• Condensed matter physics
• Physics
• Nanotechnology

Selected publications

• Unconventional solitonic high-temperature superfluorescence from perovskites

  Nature · 2025-05-28 · 10 citations

  articleOpen access
  PublisherOA PDFDOI

• Unified Voice and Group Agency: Developing Teams to Transform Engineering Education

  2021 ASEE Virtual Annual Conference Content Access Proceedings · 2024-02-20 · 3 citations

  articleOpen access

  Abstract This research paper investigates how individual change agents come together to form effective teams. Improving equity within academic engineering requires changes that are often too complex and too high-risk for a faculty member to pursue on their own [1], [2]. Teams offer the advantage of combining a diverse skill set of many individuals, as well as bringing together insider knowledge and external specialist expertise [1], [2]. However, in order for teams of academic change agents to function effectively, they must overcome the challenges of internal politics, power differentials, and group conflict [1]. This analysis of team formation emerges from our participatory action research with recipients of the NSF Revolutionizing Engineering Departments (RED) grants. Through an NSF-funded collaboration between [University 1] and [University 2], we work with the RED teams to research the process of change as they work to improve equity and inclusion within their institutions. Utilizing longitudinal qualitative data from focus group discussions with 16 teams at the beginning and midpoints of their projects, we examine the development of teams to transform engineering education. Drawing on theoretical frameworks from social movement theory, we highlight the importance of creating a unified team voice and developing a sense of group agency. Teams have a better chance of achieving their goals if members are able to create a unified voice—that is, a shared sense of purpose and vision for their team [3], [4], [5]. We find that the development of a team's unified voice begins with proposal writing. When members of RED teams did not collaboratively write the grant proposal, they found it necessary to devote more time to develop a sense of shared vision for their project. For many RED teams, the development of a unified voice was further strengthened through external messaging, as they articulated a "we" in opposition to a "they" who have different values or interests [3], [4]. Group agency develops as a result of team members perceiving their goals as attainable and their efforts, as both individuals and a group, as worthwhile [4]. That is, group agency is dependent on both the credibility of the team as well as trust among team members [6]. For some of the RED teams, the NSF requirement to include social scientists and education researchers on their teams gave the engineering team members new, increased exposure to these fields. RED teams found that creating mutual respect was foundational for working across disciplinary differences and developing group agency. References [1] R. Caldwell, "Models of change agency: A fourfold classification," British Journal of Management, vol. 14, no. 2, pp. 131-142, 2003. [2] J.R. Hackman and A.C. Edmondson, "Groups as agents of change," Handbook of organization development, 2008, pp. 167-186. [3] K.M. Blee, Democracy in the making: How activist groups form, New York, NY: Oxford University Press, 2012. [4] K. Dugan and J. Reger, "Voice and agency in social movement outcomes," Qualitative Sociology, vol. 29, no. 4, pp. 467-484, 2006. [5] J.R. Katzenbach and D.K. Smith, "The discipline of teams," Harvard Business Review, vol. 83, no. 7, p. 162, 1993. [6] J.P. Kotter, J. P., Leading Change, Boston, Mass.: Harvard Business School Press, 1996.

  PublisherOA PDFDOI

• Deterministic Localization of Strain-Induced Single-Photon Emitters in Multilayer GaSe

  ACS Photonics · 2023-07-27 · 20 citations

  articleOpen access

  The nanoscale strain has emerged as a powerful tool for controlling single-photon emitters (SPEs) in atomically thin transition metal dichalcogenides (TMDCs). However, quantum emitters in monolayer TMDCs are typically unstable in ambient conditions. Multilayer TMDCs could be a solution, but they suffer from low quantum efficiency, resulting in low brightness of the SPEs. Here, we report the deterministic spatial localization of strain-induced SPEs in multilayer GaSe by nanopillar arrays. The strain-controlled quantum confinement effect introduces well-isolated sub-bandgap photoluminescence and corresponding suppression of the broad band edge photoluminescence. Clear photon-antibunching behavior is observed from the quantum dot-like GaSe sub-bandgap exciton emission at 3.5 K. The strain-dependent confinement potential and the brightness are found to be strongly correlated, suggesting a promising route for tuning and controlling SPEs. The comprehensive investigations of strain-engineered GaSe SPEs provide a solid foundation for the development of 2D devices for quantum photonic technologies.

  PublisherOA PDFDOI

• Imaging Strain-Localized Single-Photon Emitters in Layered GaSe below the Diffraction Limit

  ACS Nano · 2023-12-04 · 7 citations

  articleOpen access

  Nanoscale strain control of exciton funneling is an increasingly critical tool for the scalable production of single photon emitters (SPEs) in two-dimensional materials. However, conventional far-field optical microscopies remain constrained in spatial resolution by the diffraction limit and thus can provide only a limited description of nanoscale strain localization of SPEs. Here, we quantify the effects of nanoscale heterogeneous strain on the energy and brightness of GaSe SPEs on nanopillars with correlative cathodoluminescence, photoluminescence, and atomic force microscopy, supported by density functional theory simulations. We report the strain-localized SPEs have a broad range of emission wavelengths from 620 to 900 nm. We reveal substantial strain-controlled SPE wavelength tunability over a ∼100 nm spectral range and 2 orders of magnitude enhancement in the SPE brightness at the pillar center due to Type-I exciton funneling. In addition, we show that radiative biexciton cascade processes contribute to observed CL photon superbunching. Also, the GaSe SPEs show excellent stability, where their properties remain unchanged after electron beam exposure. We anticipate that this comprehensive study on the nanoscale strain control of two-dimensional SPEs will provide key insights to guide the development of truly deterministic quantum photonics.

  PublisherOA PDFDOI

• Improving Strain-localized GaSe Single Photon Emitters with Electrical Doping

  Nano Letters · 2023-10-25 · 12 citations

  articleOpen access

  Exciton localization through nanoscale strain has been used to create highly efficient single-photon emitters (SPEs) in 2D materials. However, the strong Coulomb interactions between excitons can lead to nonradiative recombination through exciton–exciton annihilation, negatively impacting SPE performance. Here, we investigate the effect of Coulomb interactions on the brightness, single photon purity, and operating temperatures of strain-localized GaSe SPEs by using electrostatic doping. By gating GaSe to the charge neutrality point, the exciton–exciton annihilation nonradiative pathway is suppressed, leading to ∼60% improvement of emission intensity and an enhancement of the single photon purity g(2)(0) from 0.55 to 0.28. The operating temperature also increased from 4.5 K to 85 K consequently. This research provides insight into many-body interactions in excitons confined by nanoscale strain and lays the groundwork for the optimization of SPEs for optoelectronics and quantum photonics.

  PublisherOA PDFDOI

• Imaging Strain-Localized Single-Photon Emitters in Layered GaSe below the Diffraction Limit

  arXiv (Cornell University) · 2023-05-05 · 1 citations

  preprintOpen access

  Nanoscale strain control of exciton funneling is an increasingly critical tool for the scalable production of single photon emitters (SPEs) in two-dimensional materials. However, conventional far-field optical microscopies remain constrained in spatial resolution by the diffraction limit and thus can only provide a limited description of nanoscale strain localization of SPEs. Here, we quantify the effects of nanoscale heterogeneous strain on the energy and brightness of GaSe SPEs on nanopillars with correlative cathodoluminescence, photoluminescence, and atomic force microscopies supported by density functional theory simulations. We report the strain-localized SPEs have a broad range of emission wavelengths from 620 nm to 900 nm. We reveal substantial strain-controlled SPE wavelength tunability over a ~ 100 nm spectral range and two-orders of magnitude enhancement in the SPE brightness at the pillar center due to Type-I exciton funneling. In addition, we show that radiative biexciton cascade processes contribute to the observed CL photon superbunching. Also, the measured GaSe SPE photophysics after electron beam exposure shows the excellent stability of these SPEs. We anticipate this insight into nanoscale strain control of two-dimensional SPEs will guide the development of truly deterministic quantum photonics.

  PublisherOA PDFDOI

• Deterministic Localization of Strain-induced Single-photon Emitters in Multilayer GaSe

  arXiv (Cornell University) · 2022-10-27

  preprintOpen access

  Nanoscale strain has emerged as a powerful tool for controlling single-photon emitters (SPEs) in atomically thin transition metal dichalcogenides (TMDCs)(1, 2). However, quantum emitters in monolayer TMDCs are typically unstable in ambient conditions. Multilayer two-dimensional (2D) TMDCs could be a solution, but they suffer from low quantum efficiency, resulting in low brightness of the SPEs. Here, we report the deterministic spatial localization of strain-induced single-photon emitters in multilayer GaSe by nanopillar arrays. The strain-controlled quantum confinement effect introduces well-isolated sub-bandgap photoluminescence and corresponding suppression of the broad band edge photoluminescence. Clear photon-antibunching behavior is observed from the quantum dot-like GaSe sub-bandgap exciton emission at 3.5 Kelvin. The strain-dependent confinement potential and the brightness are found to be strongly correlated, suggesting a promising route for tuning and controlling SPEs. The comprehensive investigations of strain-engineered GaSe SPEs provide a solid foundation for the development of 2D devices for quantum photonic technologies.

  PublisherOA PDFDOI

• Identifying charge density and dielectric environment of graphene using Raman spectroscopy and deep learning

  arXiv (Cornell University) · 2022-02-25

  preprintOpen accessSenior author

  The impact of the environment on graphene's properties such as strain, charge density, and dielectric environment can be evaluated by Raman spectroscopy. These environmental interactions are not trivial to determine, since they affect the spectra in overlapping ways. Data preprocessing such as background subtraction and peak fitting is typically used. Moreover, collected spectroscopic data vary due to different experimental setups and environments. Such variations, artifacts, and environmental differences pose a challenge in accurate spectral analysis. In this work, we developed a deep learning model to overcome the effects of such variations and classify graphene Raman spectra according to different charge densities and dielectric environments. We consider two approaches: deep learning models and machine learning algorithms to classify spectra with slightly different charge density or dielectric environment. These two approaches show similar success rates for high Signal-to-Noise data. However, deep learning models are less sensitive to noise. To improve the accuracy and generalization of all models, we use data augmentation through additive noise and peak shifting. We demonstrated the spectra classification with 99% accuracy using a convolutional neural net (CNN) model. The CNN model is able to classify Raman spectra of graphene with different charge doping levels and even subtle variation in the spectra between graphene on SiO$_2$ and graphene on silanized SiO$_2$. Our approach has the potential for fast and reliable estimation of graphene doping levels and dielectric environments. The proposed model paves the way for achieving efficient analytical tools to evaluate the properties of graphene.

  PublisherDOI

• Charge Separation in Monolayer WSe₂ by Strain Engineering: Implications for Strain-Induced Diode Action

  ACS Applied Nano Materials · 2022 · 19 citations

  Senior authorCorresponding
  • Materials science
  • Condensed matter physics
  • Optoelectronics

  Strain-engineering band structure in transition-metal dichalcogenides (TMDC) is a promising avenue toward capabilities in optoelectronics. For example, controlling the flow of optically generated quasiparticles can be achieved by a localized strain field which reduces the bandgap and generates an energy-band gradient that funnels neutral excitons to the strain apex. It would be even more advantageous to mimic a diode’s internal field, where both conduction and valence bands bend in the same direction, to separate electrons and holes. This can be achieved if the strain in the TMDC layer lowers both the conduction band minimum as well as the valence band maximum during strain-induced band narrowing. Here, we have used density functional theory (DFT) calculations of monolayer WSe2 electronic structure under biaxial strain to show that WSe2 has this property. To test the band bending experimentally, we combined localized strain with electrostatic doping to follow photoluminescence from excitons and positive or negative trions. In unstrained WSe2, both positive and negative trion emissions dominate over excitons away from charge neutrality. In contrast, for strained areas, negative trions accumulate, while positive trion emission is near zero away from charge neutrality, indicating a lack of holes. Hence, strain bends both conduction and valence bands down, similarly to the band bending in a PN-diode depletion region, providing an opportunity to separate electrons and holes via localized strain.

  PublisherOA PDFDOI

• Graphene metasurfaces for terahertz wavefront shaping and light emission [Invited]

  Optical Materials Express · 2022-10-28 · 6 citations

  articleOpen access

  Graphene is a promising materials platform for metasurface flat optics at terahertz wavelengths, with the important advantage of active tunability. Here we review recent work aimed at the development of tunable graphene metasurfaces for THz wavefront shaping (including beam-steering metamirrors and metalenses) and light emission. Various design strategies for the constituent meta-units are presented, ranging from metallic phase-shifting elements combined with a nearby graphene sheet for active tuning to graphene plasmonic resonators providing the required phase control or radiation mechanism. The key challenge in the development of these devices, related to the limited radiative coupling of graphene plasmonic excitations, is discussed in detail together with recently proposed solutions. The resulting metasurface technology can be expected to have a far-reaching impact on a wide range of device applications for THz imaging, sensing, and future wireless communications.

  PublisherDOI

Recent grants

• Strain physics in graphene - from friction to pseudo magnetic fields

  NSF · $539k · 2014–2019

• Nanometer Resolution Spectral Self-interference Fluorescence Microscopy

  NSF · $548k · 2002–2007

• Vibrational and Electronic Aspects of Carbon Nanotubes and their Interactions

  NSF · $307k · 2007–2011

Frequent coauthors

• Bennett B. Goldberg

  Boston University

  140 shared

• M. Selim Ünlü

  Boston University

  92 shared

• Stephen B. Cronin

  University of Southern California

  35 shared

• Yan Yin

  Xinjiang Institute of Engineering

  34 shared

• Wolfgang Bacsa

  Centre d’Élaboration de Matériaux et d’Études Structurales

  32 shared

• Jason Christopher

  Sandia National Laboratories

  25 shared

• M. Tinkham

  Harvard University Press

  25 shared

• A. G. Souza Filho

  Universidade Federal do Ceará

  23 shared

Labs

• PhysicsPI

Education

• PhD, Physics

  Boston University

  1994

• BSc, Physics Engineering

  Chalmers tekniska högskola

  1986