Tuning of Fano resonances by rotation of continuum: Wave faucet

Rapid ionization of Cs vapor in a heat pipe at 0.05 torr was achieved by pumping the 6s 2S½ – 7p 2P½ transition (f=0.007)1 with a flash-pumped dye laser at 4593.2A and I MW power output. Photoabsorptian initiated at the end of the laser pulse(≃ 0.5/s) showed the 5p5ns and nd series below and above the 5p52P3/2 threshold at 535.4A. Broad Beutler - Fano resonances appeared in the d series above threshold. The spectrum was recorded photographically on a 10.7m grazing incidence spectrograph using a continuum background generated by a BRV high-voltage spark source with a uranium anode. We will compare the line-shapes and the quantum defect (Lu-Fano2) plot with the predictions of a relativistic random phase calculation.

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Active nonlocal metasurfaces

Nanophotonics ◽

10.1515/nanoph-2020-0375 ◽

2020 ◽

Vol 10 (1) ◽

pp. 655-665

Author(s):

Stephanie C. Malek ◽

Adam C. Overvig ◽

Sajan Shrestha ◽

Nanfang Yu

Keyword(s):

Bound States ◽

Fano Resonances ◽

Spatial Control ◽

Technical Challenge ◽

Materials Engineering ◽

Narrow Bandwidth ◽

Wavefront Shaping ◽

Mechanical Stretching ◽

Proof Of Principle ◽

The Continuum

AbstractActively tunable and reconfigurable wavefront shaping by optical metasurfaces poses a significant technical challenge often requiring unconventional materials engineering and nanofabrication. Most wavefront-shaping metasurfaces can be considered “local” in that their operation depends on the responses of individual meta-units. In contrast, “nonlocal” metasurfaces function based on the modes supported by many adjacent meta-units, resulting in sharp spectral features but typically no spatial control of the outgoing wavefront. Recently, nonlocal metasurfaces based on quasi-bound states in the continuum have been shown to produce designer wavefronts only across the narrow bandwidth of the supported Fano resonance. Here, we leverage the enhanced light-matter interactions associated with sharp Fano resonances to explore the active modulation of optical spectra and wavefronts by refractive-index tuning and mechanical stretching. We experimentally demonstrate proof-of-principle thermo-optically tuned nonlocal metasurfaces made of silicon and numerically demonstrate nonlocal metasurfaces that thermo-optically switch between distinct wavefront shapes. This meta-optics platform for thermally reconfigurable wavefront shaping requires neither unusual materials and fabrication nor active control of individual meta-units.

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Graphene–polyimide-integrated metasurface for ultrasensitive modulation of higher-order terahertz fano resonances at the Dirac point

Applied Surface Science ◽

10.1016/j.apsusc.2021.150182 ◽

2021 ◽

pp. 150182

Author(s):

Maosheng Yang ◽

Tengteng Li ◽

Ju Gao ◽

Xin Yan ◽

Lanju Liang ◽

...

Keyword(s):

Dirac Point ◽

Higher Order ◽

Fano Resonances

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Tailoring exceptional points in a hybrid PT-symmetric and anti-PT-symmetric scattering system

Nanophotonics ◽

10.1515/nanoph-2021-0245 ◽

2021 ◽

Vol 0 (0) ◽

Author(s):

Zhicheng Xiao ◽

Andrea Alù

Keyword(s):

High Resolution ◽

Real Time ◽

Quantum Systems ◽

Symmetric System ◽

Microwave Circuit ◽

High Resolution Imaging ◽

Fano Resonances ◽

Real Time Control ◽

Time Control ◽

Resolution Imaging

Abstract Fano resonances feature an asymmetric lineshape with controllable linewidth, stemming from the interplay between bright and dark resonances. They provide efficient opportunities to shape the scattering lineshape, but they usually lack flexibility and tunability and are hindered by loss in passive systems. Here, we explore a hybrid parity-time (PT) and anti-parity-time (APT) symmetric system supporting unitary scattering features with highly tunable Fano resonances. The PT-APT-symmetric system can be envisioned in nanophotonic and microwave circuit implementations, allowing for real-time control of the scattering lineshape and its underlying singularities. Our study shows the opportunities enabled by non-Hermitian platforms to control scattering lineshapes for a plethora of photonic, electronic, and quantum systems, with potential for high-resolution imaging, switching, sensing, and multiplexing.

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