Unveiling the Symmetry Protection of Bound States in the Continuum with Terahertz Near-Field Imaging

Hoof, Niels J. J. van; Abujetas, Diego R.; Huurne, Stan ter; Verdelli, Francesco; Timmermans, Giel C.A.; Sánchez‐Gil, José A.; Rivas, Jaime Gómez

doi:10.1021/acsphotonics.1c00937

Cited by 32 publications

(17 citation statements)

References 47 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This transformation manifests itself in the metasurface spectra as a resonance with a quality factor depending on the degree of the introduced asymmetry. − The use of specific irradiation conditions (structured light, near-field sources, etc.) is another possible way to realize quasi-BIC excitation in metasurfaces. , Nevertheless, for both these cases, the implementation of the high-quality factor resonances requires special tuning or modification of the properties of the overall optical system.…”

Section: Introductionmentioning

confidence: 99%

Resonant Light Trapping via Lattice-Induced Multipole Coupling in Symmetrical Metasurfaces

et al. 2022

View full text Add to dashboard Cite

We demonstrate a general multipole mechanism of the resonant mode trapping effect in metasurfaces composed of MoS 2 disk-shaped nanoresonators. The implementation of this mechanism does not require any special irradiation conditions for the incident light or geometrical distortion of the symmetry of the metasurface translation unit cell. It is established that the effect arises due to the periodic-lattice-induced coupling between the electric dipole and electric octupole modes existing in the nanoresonators. We show that, under these conditions, the resonant quasi-trapped octupole mode and the suppression of the electric dipole response can be self-consistently realized under the action of normally incident plane waves. This, in turn, leads to the appearance of a narrowband-induced transparency of the metasurface supplemented by the strong electromagnetic energy storage in the nanoresonators. Due to its general nature, the presented mechanism can be implemented in various dielectric and semiconductor metasurfaces, whose meta-atoms support resonant excitation conditions for different-order multipole moments with the same inverse symmetry property.

show abstract

Section: Introductionmentioning

confidence: 99%

Resonant Light Trapping via Lattice-Induced Multipole Coupling in Symmetrical Metasurfaces

et al. 2022

View full text Add to dashboard Cite

show abstract

“…These oscillations and resonance are thus unambiguously attributed to the symmetry protected BIC in the resonant metasurface that can be only probed in the near‐field. [ 30 ] The electric field amplitude at the BIC frequency is significantly enhanced close to the surface, reaching a 25‐fold enhancement at the surface. This amplitude enhancement corresponds to a 625 times intensity enhancement.…”

Section: Resultsmentioning

confidence: 99%

“…The extraordinary properties of BICs has led to significant interest in recent years, including research in nonlinear optics, ultrastrong coupling, optical sensing, low threshold lasing, or polarization filtering. [23][24][25][26][27][28] However, the direct investigation of BICs has remained elusive since they do not interact with the far-field, [29,30] and most of the research has focused on quasi-BICs where radiative losses are still significant.In this manuscript, we use a unique near-field microscope capable of locally exciting and detecting terahertz (THz) radiation in the time-domain to investigate the lateral field confinement of a symmetry protected BIC on a metasurface of resonant gold rods at THz frequencies. Noble metals have very large permittivities in the THz range, leading to slim skin depths and negligible material losses.…”

mentioning

confidence: 99%

mentioning

confidence: 99%

See 1 more Smart Citation

Direct Observation of Lateral Field Confinement in Symmetry‐Protected THz Bound States in the Continuum

Huurne

Abujetas

Hoof

et al. 2023

Advanced Optical Materials

Self Cite

View full text Add to dashboard Cite

Electromagnetic wave scattering by resonators is an effective way of localizing radiation on sub-wavelength scales at the surface and increasing the interaction strength with matter. [6][7][8][9][10] The resonant response of scatterers at defined frequencies leads to the strong localization of the field. [11][12][13][14] However, these resonances are spectrally broad, thus with very short lifetimes due to large radiation losses. This can be improved by combining resonant scattering with surface waves in metasurfaces. The coherent coupling of the scatterers with in-plane diffraction leads to the reduction of radiation losses by destructive interference. In this respect, surface lattice resonances (SLRs) in periodic arrays of resonant scatterers represent a great advancement. [15][16][17][18][19][20] On the other hand, bound states in the continuum (BICs) are eigenstates of resonant systems that exist inside the continuum of states but do not interact with them. [21,22] Therefore, resonant metasurfaces supporting BICs offer a unique opportunity to achieve strong field confinements by the full suppression of the radiation leakage, while still having the localized resonant response of the scatterers. The extraordinary properties of BICs has led to significant interest in recent years, including research in nonlinear optics, ultrastrong coupling, optical sensing, low threshold lasing, or polarization filtering. [23][24][25][26][27][28] However, the direct investigation of BICs has remained elusive since they do not interact with the far-field, [29,30] and most of the research has focused on quasi-BICs where radiative losses are still significant.In this manuscript, we use a unique near-field microscope capable of locally exciting and detecting terahertz (THz) radiation in the time-domain to investigate the lateral field confinement of a symmetry protected BIC on a metasurface of resonant gold rods at THz frequencies. Noble metals have very large permittivities in the THz range, leading to slim skin depths and negligible material losses. The near-field microscope allows us to locally break the symmetry by exciting a single resonator and measure the field confinement associated to the BIC on the metasurface as a function of position, height, and time. We demonstrate that the confinement of the BIC in the lateral direction is strong (λ/38 in amplitude) for high Q resonances with very long lifetimes of over 50 ps. This confinement is experimentally compared with other resonances in similar structures, such as quasi-BICs and SLRs, showing a significantly larger field enhancement and confinement for BICs. This first investigation and demonstration of the field Electromagnetic field confinement on sub-wavelength scales is possible at the expense of increasing optical losses. Examples are surface plasmon polaritons and resonant structures, which suffer from absorption losses and radiative outcoupling, respectively. Here, the first experimental evidence of strong electromagnetic field confinement along the lateral (out-of-plan...

show abstract

“…Recently, researches proposed symmetrical structures to discuss BIC with photonic crystals and metasurfaces [4][5][6][7][8][9][10][11]. Grating as a high-performance structure is researched in many fields, and it is suitable as a highly symmetrical structure for the study of BIC.…”

Section: Introductionmentioning

confidence: 99%

Adjacent Asymmetric Tilt Grating Structure With Strong Resonance Assisted by Quasi-Bound States in the Continuum

Ruan

Wang

et al. 2022

IEEE Photonics J.

View full text Add to dashboard Cite

In the field of optics, bound state in the continuum (BIC) as a special state to be researched in many photonic crystals and periodic structures, which can produce strong resonance and an ultrahigh Q factor. Some designs of narrowband transmission filters, lasers, and sensors are proposed based on excellent optical properties of quasi-BIC. In this paper, we consider symmetrical rectangular grating structure firstly. Then cut off a corner of rectangular gratings, the Fano line of quasi-BIC can be observed in the spectrum. After that, we change the oblique parameter of the other rectangular grating, which can further decrease the Fano line width. In the momentum space, the change of structure means topological charges split from q=1 into half charges q=1/2. We analyze guided mode resonance (GMR) excitation of the grating structure, and discuss the dispersion relations in the waveguide layer with the position of BIC in energy bands. In addition, the spectrum exhibits asymmetric line-shapes with different values of the asymmetry parameters, M1 and M2. BIC is transformed into quasi-BIC as the symmetry of the structure broken. Thus, a large Goos-Hänchen shift can be achieved as a result of ultrahigh Q factor of quasi-BIC. This work demonstrates a double trapezoid structure with strong resonance properties, which has significant implications for exploring the phenomenon of BIC.

show abstract

Unveiling the Symmetry Protection of Bound States in the Continuum with Terahertz Near-Field Imaging

Cited by 32 publications

References 47 publications

Resonant Light Trapping via Lattice-Induced Multipole Coupling in Symmetrical Metasurfaces

Resonant Light Trapping via Lattice-Induced Multipole Coupling in Symmetrical Metasurfaces

Direct Observation of Lateral Field Confinement in Symmetry‐Protected THz Bound States in the Continuum

Adjacent Asymmetric Tilt Grating Structure With Strong Resonance Assisted by Quasi-Bound States in the Continuum

Contact Info

Product

Resources

About