Active high-Q dielectric terahertz supercavities

Han, Song; Cong, Longqing; Srivastava, Yogesh Kumar; Qiang, Bo; Rybin, Mikhail V.; Lim, Wen Xiang; Wang, Qi Jie; Kivshar, Yuri S.; Singh, Ranjan

doi:10.1364/cleo_si.2018.sw4d.6

Cited by 3 publications

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“…Thus, optical BICs are grounded in confined (nonleaky) modes with an infinite lifetime above the light line in the dispersion diagram of periodic structures. Well established symmetry‐protected BICs with exact zero resonance bandwidth (true BIC) reside at the Γ point of the band diagram based on the symmetry incompatibility between the asymmetric standing waves inside the structure and symmetric outgoing waves . In addition, it has been shown both theoretically and experimentally that off‐Γ BIC, with near‐zero resonance linewidth (quasi‐BIC or asymptotic BIC) can be obtained at specific incident angles in periodic structures .…”

Section: Introductionmentioning

confidence: 99%

Resonant Dual‐Grating Metamembranes Supporting Spectrally Narrow Bound States in the Continuum

Hemmati

Magnusson

2019

Advanced Optical Materials

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second-order Bragg condition was satisfied. Later, in 1979, Vincent and Neviere numerically demonstrated the existence of a nonleaky edge pertinent to symmetric grating designs while introducing asymmetry to the grating profile resulted in leaky radiating modes at both band edges. [4] Ding and Magnusson manipulated the separation of the nondegenerate leaky resonances associated with asymmetric profiles to engineer the resonant spectral response of periodic films. [5] Experimentally, the nonleaky edge, and thus BIC, was revealed in 1998 by imposing asymmetry on an otherwise symmetric periodic structure by variation in the angle of incidence. [6] Thus, optical BICs are grounded in confined (nonleaky) modes with an infinite lifetime above the light line in the dispersion diagram of periodic structures. Well established symmetry-protected BICs with exact zero resonance bandwidth (true BIC) reside at the Γ point of the band diagram based on the symmetry incompatibility between the asymmetric standing waves inside the structure and symmetric outgoing waves. [7][8][9][10][11][12] In addition, it has been shown both theoretically and experimentally that off-Γ BIC, with nearzero resonance linewidth (quasi-BIC or asymptotic BIC) can be obtained at specific incident angles in periodic structures. [13][14][15] Moreover, quasi-BICs at the Γ point were reported for specific physical parameters of nanostructures. [16] These nearly zero resonance linewidths possess quasiembedded eigenvalues which cause coupling to the radiated waves.Whereas there have been extensive studies conducted on metamaterial devices with a single spatial periodicity, [17][18][19][20][21][22][23] there is less research on resonance elements containing multiple spatial periodic layers. Unquestionably, there are additional design dimensions to be exploited with such architectures as any multiperiodic construct will operate on available bound modes differently than a single periodicity. Thus, there are scientific and practical reasons to explore attendant device designs and corresponding spectral response. Past related work includes demonstration that properly designed dually corrugated waveguides support unidirectional output radiation. [24] Similar elements were advanced as solutions to improve the efficiency and stability of second-order surface emitting laser diodes via substrate radiation suppression. [24,25] In 2014, a unidirectional coupler for surface plasmon polaritons was proposed and Properties of photonic devices fashioned with dual-grating metamaterials are reported. Enclosed by dual periodic regions, laterally propagating Bloch modes undergo radiative scattering and leaky-mode resonance whose properties differ markedly from those with single periodicity. The resonance signatures are sensitively controlled by the relative parameters of the periodic regions. In particular, if they are physically identical and separated by a half-wavelength, there ensues a bound state in the continuum (BIC) with extremely narrow resonance linewidth. On varying the...

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Section: Introductionmentioning

confidence: 99%

Resonant Dual‐Grating Metamembranes Supporting Spectrally Narrow Bound States in the Continuum

Hemmati

Magnusson

2019

Advanced Optical Materials

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“…Dielectric photonic crystals (PhCs) are an excellent platform to explore the BICs which largely avoid the intrinsic Ohmic loss for extremely high Q generation by exciting displacement current . Nevertheless, the geometric size of unit cells in PhCs is usually at the scale of resonance wavelength, and resonant energy is thus loosely confined in the resonator cavity with a relatively large mode volume ( V ).…”

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confidence: 99%

Symmetry‐Protected Dual Bound States in the Continuum in Metamaterials

Cong

Singh

2019

Advanced Optical Materials

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to access extreme confinement of photons into micro-or nanoscale region [3,10,11] above the light line within the radiation continuum. In general, EM wave is usually interpreted in terms of frequency spectrum, and it propagates as a spectral continuum above the light line in different media. Different orders of resonances may be found in the propagating continuum at specific frequencies described by i n n n 0  ω ω γ = + , where the real part indicates resonance frequencies and the imaginary part indicates the leakage rates of the n-order mode. [12] For a strongly confined mode, the leakage rate is significantly reduced, and goes to zero if photons are perfectly trapped in a so-called bound state in an ideal scenario. [13] However, such a bound state in the continuum (BIC) is not observable from the spectrum due to the nonradiative feature with vanishing spectral linewidth. As an embedded eigenvalue of the photonic system, [14] it becomes visible in the spectrum with a finite leakage rate as a quasi-BIC by introducing external perturbations. Such a BIC-inspired mechanism for light confinement allows a general strategy to access extremely high quality factor (Q, Q = ω 0 /2γ) resonance in optical cavities.Dielectric photonic crystals (PhCs) are an excellent platform to explore the BICs which largely avoid the intrinsic Ohmic loss for extremely high Q generation by exciting displacement current. [15,16] Nevertheless, the geometric size of unit cells in PhCs is usually at the scale of resonance wavelength, and resonant energy is thus loosely confined in the resonator cavity with a relatively large mode volume (V). In this condition, Purcell factor proportional to Q/V is largely reduced in the traditional PhCs despite a large Q, which hinders the efficient spontaneous emission rates in the context of cavity quantum electrodynamics. [17] An efficient approach to densely confine photons is by using metamaterials whose building blocks are in the subwavelength scale, and the resonant mode volume could be further reduced to a deep subwavelength scale by carefully designing the resonator geometry and mode properties. Here, we demonstrate dual symmetry-protected BICs in a subwavelength metamaterial that are independently induced by orthogonal polarizations of incident light. The features of the subwavelength BICs are experimentally observed in the terahertz spectrum by slightly breaking the C 2 symmetry with large Q factors. We also show the inverse square dependence of Q factor on the structural asymmetry parameter which describes a Bound state in the continuum (BIC) is a mathematical concept with an infinite radiative quality factor (Q) that exists only in an ideal infinite array of resonators. In photonics, it is essential to achieve high Q resonances for enhanced light-mater interactions that could enable low-threshold lasers, ultrasensitive sensors, and optical tweezers. Hence, it is important to explore BICs in different photonic systems including subwavelength metamaterials where symmetry-protected dual BICs exist. Th...

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“…This includes, in particular, broken-symmetry Fano dielectric metasurfaces for enhancement of nonlinear effects [49] and recently reported biosensing with pixelated dielectric metasurfaces [50]. Currently, quasi-BICs in alldielectric structures have been shown to be advantageous for a wide span of applications, including lasing [35,36], active photonics [51], polaritonics [42] and biophotonics [37,38].…”

Section: Introductionmentioning

confidence: 99%

Meta-optics and bound states in the continuum

2019

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We discuss the recent advances in meta-optics and nanophotonics associated with the physics of bound states in the continuum (BICs). Such resonant states appear due to a strong coupling between leaky modes in optical guiding structures being supported by subwavelength high-index dielectric Mie-resonant nanoantennas or alldielectric metasurfaces. First, we review briefly very recent developments in the BIC physics in application to isolated subwavelength particles. We pay a special attention to novel opportunities for nonlinear nanophotonics due to the large field enhancement inside the particle volume creating the resonant states with high-quality (high-Q) factors, the so-called quasi-BIC, that can be supported by the subwavelength particles. Second, we discuss novel applications of the BIC physics to all-dielectric optical metasurfaces with broken-symmetry metaatoms when tuning to the BIC conditions allows to enhance substantially the Q factor of the flat-optics dielectric structures. We also present the original results on nonlinear high-Q metasurfaces and predict that the frequency conversion efficiency can be boosted dramatically by smart engineering of the asymmetry parameter of dielectric metasurfaces in the vicinity of the quasi-BIC regime. arXiv:1810.08698v1 [physics.optics]

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Active high-Q dielectric terahertz supercavities

Cited by 3 publications

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Resonant Dual‐Grating Metamembranes Supporting Spectrally Narrow Bound States in the Continuum

Resonant Dual‐Grating Metamembranes Supporting Spectrally Narrow Bound States in the Continuum

Symmetry‐Protected Dual Bound States in the Continuum in Metamaterials

Meta-optics and bound states in the continuum

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