Directive giant upconversion by supercritical bound states in the continuum
- Italian National Research Council (INRC), Naples (Italy)
- Italian National Research Council (INRC), Pozzuoli (Italy)
- Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States). Molecular Foundry
- National Univ. of Singapore (Singapore)
- National Univ. of Singapore (Singapore); Agency for Science, Technology and Research (A*STAR) (Singapore)
Photonic bound states in the continuum (BICs), embedded in the spectrum of free-space waves with diverging radiative quality factor, are topologically non-trivial dark modes in open-cavity resonators that have enabled important advances in photonics. However, it is particularly challenging to achieve maximum near-field enhancement, as this requires matching radiative and non-radiative losses. Here we propose the concept of supercritical coupling, drawing inspiration from electromagnetically induced transparency in near-field coupled resonances close to the Friedrich–Wintgen condition. Supercritical coupling occurs when the near-field coupling between dark and bright modes compensates for the negligible direct far-field coupling with the dark mode. This enables a quasi-BIC field to reach maximum enhancement imposed by non-radiative loss, even when the radiative quality factor is divergent. Our experimental design consists of a photonic-crystal nanoslab covered with upconversion nanoparticles. Near-field coupling is finely tuned at the nanostructure edge, in which a coherent upconversion luminescence enhanced by eight orders of magnitude is observed. The emission shows negligible divergence, narrow width at the microscale and controllable directivity through input focusing and polarization. This approach is relevant to various physical processes, with potential applications for light-source development, energy harvesting and photochemical catalysis.
- Research Organization:
- Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)
- Sponsoring Organization:
- National Research Council, Italy; National Research Foundation of Korea (NRF); USDOE Office of Science (SC), Basic Energy Sciences (BES)
- Grant/Contract Number:
- AC02-05CH11231
- OSTI ID:
- 2429230
- Journal Information:
- Nature (London), Journal Name: Nature (London) Journal Issue: 8000 Vol. 626; ISSN 0028-0836
- Publisher:
- Nature Publishing GroupCopyright Statement
- Country of Publication:
- United States
- Language:
- English
Similar Records
Formation of Bound States in the Continuum in Hybrid Plasmonic-Photonic Systems
Achieving extreme light confinement in low-index dielectric resonators through quasi-bound states in the continuum
Journal Article
·
Wed Dec 19 19:00:00 EST 2018
· Physical Review Letters
·
OSTI ID:1612747
Achieving extreme light confinement in low-index dielectric resonators through quasi-bound states in the continuum
Journal Article
·
Mon Dec 13 19:00:00 EST 2021
· Optics Letters
·
OSTI ID:1968729