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DARKENET: Engineering dark modes for energy trapping

DARKENET: Engineering dark modes for energy trapping

Vikas Remesh (ORCID: 0000-0003-2029-0570)
  • Grant DOI 10.55776/TAI556
  • Funding program 1000 Ideas
  • Status ended
  • Start September 1, 2021
  • End June 30, 2024
  • Funding amount € 150,725
  • Project website
  • E-mail

Disciplines

Physics, Astronomy (100%)

Keywords

    Quantum Dots, Subradiance, Energy Trapping

Abstract Final report

Growing energy requirements of the world have made scientists work towards tapping more from sustainable resources like solar energy. A major challenge in this direction so far has been about improving efficiency of solar cell devices. Surprisingly, for millions of years, nature has been performing the most efficient energy capture and transfer process known to us: photosynthesis. It is through this process that plants, algae, and bacteria collect solar energy and store it as chemical energy to sustain life on this planet. In the first steps of photosynthesis, sunlight is captured by ring-shaped chlorophyll molecules (called LH2s), then transported from one molecule to another and eventually to reaction centres where it is stored for subsequent chemical reactions. This energy transport and trapping process has efficiencies close to 100%, something that invited a great deal of curiosity among physicists and chemists alike in the last few decades. The LH2, from a physics perspective, is simply a ring of electric dipoles whose interactions depend on their separations and relative orientations. For separations smaller than the optical wavelengths, these interactions result in an energy landscape containing areas with suppressed radiative properties or longer lifetimes, compared to those of individual dipoles. These areas are called dark states. It is then intuitive to assume that in LH2s, nature has optimized such dark states to trap the solar energy efficiently for longer times before transferring it to the reaction centre. With the help of ultrafast lasers, energy transport studies on single LH2s with femtosecond time-resolution have been made possible. However, those were extremely challenging, due to their limited photostability and low quantum efficiency. In this project, awarded by the FWF as part of the 1000 Ideas Program, a group of physicists from Innsbruck, led by Vikas Remesh of the Innsbruck Photonics Group, in collaboration with researchers from Canada, wants to create a simulator system using quantum dots (QD) to study the collective radiative effects in LH2. QDs are semiconductor nanocrystals, widely regarded as artificial atoms due to their discrete energy levels that can be controlled precisely by their fabrication parameters. In contrast to single LH2 molecules, QDs are bright and extremely stable emitters that can be patterned to arbitrary separations and structures with high accuracy. They provide us with a chance to solve the important task of decoding the physics of natures evolution-optimized light harvesting- trapping system. After realising QD-ring structures, the researchers plan to set up an optical microscope with an ultrafast laser and highly sensitive detectors to investigate the spatial properties of dark-state assisted energy transport. Are dark states the secret behind nature`s highly efficient photosynthetic energy transport mechanism? There is only one way to know.

Growing energy requirements of the world have made scientists work towards tapping more from sustainable resources like solar energy. A major challenge in this direction so far has been about improving efficiency of solar cell devices. For millions of years, nature has been performing the most efficient energy capture and transfer process known to us: photosynthesis. It is through this process that life sustains on this planet. In the first steps of photosynthesis, sunlight is captured by a collective molecular system, before it is stored for subsequent chemical reactions. This energy transport and trapping process has efficiencies close to 100%, something that invited a great deal of curiosity among physicists and chemists alike in the last few decades. It is proposed that when emitters are placed within small separations, it enables strong interaction between them and collective states with suppressed radiative properties may evolve. These states are thought to be the reason behind the efficient energy trapping in the natural light harvesting systems. However, despite a reasonably large number of theoretical works on this area, detailed experimental investigations are still missing, which limits our understanding and perhaps a streamlined effort to engineer artificial light harvesting systems. In this project, we wanted to create a simulator system using quantum dots to study the collective radiative effects in light harvesting complexes. Quantum dots are semiconductor nanocrystals, carrying discrete energy levels which are tunable via growth methods and post-growth tuning knobs. They are bright, and photostable systems and have been well studied in the recent past under various optical coherent control techniques. We started with a model system of nanowire quantum dots arranged in rings to emulate natural light-harvesting systems to look for coherent coupling effects. However, it turns out that the current growth parameters of this system forbid any significant inter-dot coupling. Therefore we have proposed a simpler test system, where multiple quantum dots are grown in the same nanowire, at various heights. This helps to investigate collective effects in a large range of couplings. This sample is currently under investigation. To enable simultaneous study of large range of coherent couplings, we are also developing a robust multiplexed microscopy technique. In parallel, an alternative system of strain-tuned quantum wells are also in development, where we believe direct dipole-dipole interactions can be achieved, in arbitrary geometries, both of which are not probably achievable in nanowire systems. Furthermore, we have also developed advanced pulse-shaping techniques in our laboratories to investigate such collectively evolving states. Proof of principle experiments have been demonstrated in our recent experiments on single quantum dots. Such experiments will soon be extended to collectively interacting quantum dots.

Research institution(s)
  • Universität Innsbruck - 100%

Research Output

  • 89 Citations
  • 14 Publications
  • 1 Fundings
Publications
  • 2025
    Title Exploring photon-number-encoded high-dimensional entanglement from a sequentially excited quantum three-level system
    DOI 10.1364/opticaq.538134
    Type Journal Article
    Author Vajner D
    Journal Optica Quantum
    Pages 99
    Link Publication
  • 2025
    Title High-purity and stable single-photon emission in bilayer WSe2 via phonon-assisted excitation
    DOI 10.1038/s42005-025-02080-7
    Type Journal Article
    Author Piccinini C
    Journal Communications Physics
    Pages 158
    Link Publication
  • 2023
    Title Single-Photon Sources for Multi-Photon Applications
    DOI 10.1002/9783527837427.ch4
    Type Book Chapter
    Author Frick S
    Publisher Wiley
    Pages 53-84
  • 2023
    Title Collective excitation of spatio-spectrally distinct quantum dots enabled by chirped pulses
    DOI 10.1088/2633-4356/acd7c1
    Type Journal Article
    Author Kappe F
    Journal Materials for Quantum Technology
    Pages 025006
    Link Publication
  • 2024
    Title Chirped Pulses Meet Quantum Dots: Innovations, Challenges, and Future Perspectives
    DOI 10.1002/qute.202300352
    Type Journal Article
    Author Kappe F
    Journal Advanced Quantum Technologies
    Link Publication
  • 2024
    Title Controlling the photon number coherence of solid-state quantum light sources for quantum cryptography
    DOI 10.1038/s41534-024-00811-2
    Type Journal Article
    Author Karli Y
    Journal npj Quantum Information
    Pages 17
    Link Publication
  • 2024
    Title Towards Photon-Number-Encoded High-dimensional Entanglement from a Sequentially Excited Quantum Three-Level System
    DOI 10.48550/arxiv.2407.05902
    Type Preprint
    Author Vajner D
  • 2024
    Title Theory of time-bin entangled photons from quantum emitters
    DOI 10.48550/arxiv.2404.08348
    Type Preprint
    Author Bracht T
  • 2024
    Title Keeping the photon in the dark: Enabling full quantum dot control by chirped pulses and magnetic fields
    DOI 10.48550/arxiv.2404.10708
    Type Preprint
    Author Kappe F
  • 2024
    Title High-purity and stable single-photon emission in bilayer WSe$_2$ via phonon-assisted excitation
    DOI 10.48550/arxiv.2406.07097
    Type Preprint
    Author Piccinini C
  • 2024
    Title Theory of time-bin-entangled photons from quantum emitters
    DOI 10.1103/physreva.110.063709
    Type Journal Article
    Author Bracht T
    Journal Physical Review A
    Pages 063709
    Link Publication
  • 2023
    Title Compact chirped fiber Bragg gratings for single-photon generation from quantum dots
    DOI 10.1063/5.0164222
    Type Journal Article
    Author Remesh V
    Journal APL Photonics
    Pages 101301
    Link Publication
  • 2023
    Title Dressed-state analysis of two-color excitation schemes
    DOI 10.1103/physrevb.107.035425
    Type Journal Article
    Author Bracht T
    Journal Physical Review B
    Pages 035425
    Link Publication
  • 2022
    Title SUPER Scheme in Action: Experimental Demonstration of Red-Detuned Excitation of a Quantum Emitter
    DOI 10.1021/acs.nanolett.2c01783
    Type Journal Article
    Author Karli Y
    Journal Nano Letters
    Pages 6567-6572
    Link Publication
Fundings
  • 2021
    Title DARKENET: Engineering dark modes for energy trapping
    Type Research grant (including intramural programme)
    Start of Funding 2021
    Funder Austrian Science Fund (FWF)

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