Kuang Zhang's research while affiliated with Harbin Institute of Technology and other places

... The investigation of high Q resonances in optics and photonics is motivated by the phenomena like nonlinearity [1], strong light-matter interaction, sensing [2], optical switch [3], [4] etc. Recently, THz technology has garnered significant interest in areas such as sensing [5], filtering [6], and slow light modulation [7], mainly due to its unique ability to penetrate dielectric materials, its low photon energy interactions, distinct spectral signature to some elements and applicability in 6G communications. The fundamental research and development of THz metamaterial with high Q resonant 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 A c c e p t e d M a n u s c r i p t response is always very important in such a context. ...

... In this regard, a more exotic materialization, termed bound states in the continuum (BICs), have emerged as the rare entry point for confining light with ultra-long radiative lifetime. [11][12][13] BICs refers to a kind of special discrete eigenstates with energy embedded in a radiative continuum yet are counterintuitively completely decoupled from the continuous spectrum of radiating waves that can carry energy away. 2,9,[14][15][16] In photonics, BICs have been widely investigated across various optical structures including gratings, [17][18][19] photonic crystals, 16,20,21 nanowire geometric superlattices, 22 metasurfaces (MSs), 1,2,23-25 and even individual subwavelength dielectric particles. ...

... Quasi-BIC is a leaky mode with a nonzero linewidth and a finite Q-factor [33]. This makes the utilization of quasi-BIC resonance for sensing a favorable choice [34][35][36]. Furthermore, the presence of loss also enables the mode to couple to the radiation channel. ...

... However, since the properties of the traditional metasurface are fixed after machining, the traditional metasurface has no active modulation capability and no multifunctional conversion capability. Therefore, the design and research of multifunctional terahertz devices by incorporating phase change materials into the design of metasurface has become one of the research hotspots, including perfect absorption, polarization conversion, continuous domain bound states (BIC), and so on [10][11][12][13][14][15][16]. ...

... Fortunately, metasurfaces have emerged as potential candidates for manipulating light in compact optical systems due to the outstanding advantages of their thinness, ease of integration, and design flexibility [24][25][26]. With the capability to flexibly manipulate the wavefront, polarization and dispersion [27,28], the metasurface allows for the generation of Bessel beams with high NA, which also implies that the metasurface can be a powerful platform for the observation and application of T spins. In addition, compared to conventional tightly focused beams (such as Gaussian beams [29]), the nondiffractive beams allow the pure T spin not restricted to the focal plane. ...

... Since the first experimental demonstration of radio frequency waves was announced in 2007, a number of methods have been proposed for producing OAM beams. These techniques include microstrip patch antennas, helical antennas [16], reflectarrays [17], traveling-wave antennas [18], circular leaky-wave antennas [19], circular antenna arrays [20,21], metasurfaces [22], spiral reflector plates [23], and twisted parabolic reflectors [24]. Sadly, because of their resonance characteristics, a large number of these OAM generators are limited to operating in a narrow frequency range. ...

... 薄膜在THz频率范围内不仅具有高导电性、导热 性以及较好的柔韧性 [21,22] , 且具有优异的生物相容 性以及可修饰性. 这些特性使得SWCNT在THz 超表面微量生物化学传感器 [23][24][25][26] 以及刚性和柔性 透明电子和光电子 [27] 等领域显示出了重要的应用 潜力 [28] . ...

... Among various geometries of transmissive double-layer metasurfaces [25,26], the most studied MIM structures aimed for the tuning by LCs consist of two continuous metallic layers perforated with slits of different shapes. Such structures were employed for tunable beam steering [27][28][29], tunable negative refractive index (so called fishnet structures) [30][31][32], and various transmission modulators operating at both microwave [33][34][35][36] and terahertz frequencies [37,38]. The main difference among these modulators is the shape of metallic slits ranging from simple rectangular holes to complex geometries which complicate the analysis of excited electromagnetic modes and the influence of the slit geometry on device performance. ...

... By contrast, multi-quasi-BIC modes attract more attention due to the advantage of having multiple resonances in a narrow spectrum and provide more possibilities for designing multifunctional sensors and modulators. In recent years, researchers have achieved triple quasi-BIC in all-dielectric metasurfaces by breaking geometric symmetries, including the periodicity, unit structure, and incidence angle [23][24][25][26][27]. However, there is a lack of research focusing on transitioning BIC points into quasi-BIC to excite tunable high-Q EIT effects. ...

... For materials with a metal component volume fraction greater than 20%, we utilize Bruggeman effective medium theory to analyze the phase transition process [27,28]. Its dielectric constant is represented as: ...