All‐Dielectric Crescent Metasurface Sensor Driven by Bound States in the Continuum

Abstract

Metasurfaces based on quasi-bound states in the continuum (quasi-BICs) constitute an emerging toolkit in nanophotonic sensing as they sustain high quality factor resonances and substantial near-field enhancements. It is demonstrated that silicon metasurfaces composed of crescent shaped meta-atoms provide tailored light-matter interaction controlled by the crescent geometry. Significantly, this metasurface not only exhibits a fundamental quasi-BIC resonance, but also supports a higher-order resonance with tunable electromagnetic field enhancement and advantageous properties for sensing. The higher-order resonance shows twice the sensitivity of the fundamental one for bulk refractive index sensing. It is further demonstrated that both the fundamental and higher-order resonances can be exploited for sensing ultrathin layers of biomolecules in air and buffer solutions. Specifically, when measuring in buffer solution, the figure of merit of the sensor, defined as the change in the spectral position of the resonance normalized to its full width at half maximum, is a factor of 2.5 larger for the higher-order resonance when compared to the fundamental one. Due to its high sensitivity and potential for straightforward microfluidic integration, the silicon crescent metasurface is ideally suited for real-time and in situ biosensing, enabling compact sensing devices for a wide range of diagnostic applications.

Terahertz Sensing for R/S Chiral Ibuprofen via All-Dielectric Metasurface with Higher-Order Resonance

“…It is worth mentioning that Wang et al presented a similar design in the optical frequency range very recently [31], but their result is different from ours. Although the geometry of our structure is similar to that in their work, the physical mechanism of resonance excitation is quite different.…”

“…Moreover, at higher-order resonance, the electric and magnetic field distributions are more sensitive to the change in the dielectric environment surrounding the structure; thus, the sensing performance of the resonance in a higher frequency is better than that of the lower-order resonance. It is worth mentioning that Wang et al presented a similar design in the optical frequency range very recently [31], but their result is different from ours. Although the geometry of our structure is similar to that in their work, the physical mechanism of resonance excitation is quite different.…”

Inverse-designed metaphotonics for hypersensitive detection

“…At GHz frequencies, this reduces chip footprint and increases device speed. At optical wavelengths, strongly localized fields provide the key to many significant effects, including low-threshold lasing, efficient nonlinear harmonic generations, high-resolution imaging, highly sensitive detection, low-power communications, enhanced security, and complex wavefront engineering [1][2][3][4][5][6][7][8][9]. However, despite impressive recent progress in this field, photonics integration still lags behind electronics, which employs now pioneering devices with characteristic scales of 10 nm or less [10,11].…”

“…Chebyshev polynomials T m (v) are a complete basis that represents any complex function on the unit circle −1 ≤ |v| ≤ 1 [29]. In (6), we use a a Cayley transform v = u−ia u+ia [31] that maps the unit circle to the positive semi-infinite space y ≥ 0 and −∞ ≤ x ≤ ∞, providing a rational series expansion that represents any analytic function Ω(u) in the complex domain. Additionally, we impose the condition β 0 = − ∞ m=1 β m to reduce Eq.…”

Bound States in the Continuum in Multipolar Lattices

“…A general wave phenomenon, BICs were first predicted in quantum mechanics [2] but today have found a variety of applications in photonics and acoustics [3][4][5][6][7]. Their strong spatial localization and high quality (Q) factor provide giant amplification of the external electric field [8] and drastically enhance the light-matter interaction [9][10][11][12], nonlinear optical effects [13][14][15][16], and the performance of lasers [17][18][19][20][21][22] and optical biosensors [23][24][25][26].…”