A bright–bright coupling mode Plasmon-induced transparency (PIT) system composedof two Dirac semimetal blocks (DSBs) with different sizes is proposed in this paper. The electromagnetic mechanism of ...this PIT system and its modulation property at mid-infrared band is analyzed by finite-difference time-domain (FDTD) method. Numerical results show that the transparent window, transparent peak and quality factor can be precisely controlled by the geometric parameters of the PIT system, the Fermi energy (EF) of the DSB and refractive index (RI) of the superstrate. The advantage of DSBs grating structure is that its permitivity functions can be adjusted handily by EF through doping or bias voltage. Compared to the PIT system based on bulk Dirac semimetals, our proposed PIT system has much smaller structure size and wider tunability. The resonant frequency of the transparent peak can shift from 17.59 THz to 34.79 THz when EF changing from 40 meV to 80 meV. The second-order nonlinearity of this DSBs system is also investigated by introducing the second-order nonlinear source. This developed Dirac semimetal PIT structure may pave the way to the development of novel THz active devices for light modulation devices, switches, biosensors and other mid-infrared devices.
We investigated the field enhancement and lifetime of tuning surface plasmon in zero-thickness nanostructured graphene patches. The graphene surface plasmon (GSP) resonance mechanism mainly ...originates from the contribution, that the periodical structure can provide strong coupling of GSP modes into the incident light field, which can enhance GSP resonance and the local field. And consequently, it facilitates the tuning of the patch modes by changing Fermi energy, carrier mobility, and superstrate refractive index, respectively. We can control precisely the resonant wavelengths, field enhancement, and lifetime of the patch GSP modes by using finite-difference time-domain (FDTD) simulation and coupled mode theory (CMT). The sensitivity is described by varying the refractive index of the superstrate. The theoretical descriptions and data fitting of lifetime of GSP modes are useful for graphene application.
Tamm-plasmon-polariton (TPP) has strong light absorption and polarization-independence, shows potential application in the optical biosensors. However, with the weak field confinement of the ...distributed Bragg reflector (DBR), the sensitivity enhancement of TPP biosensors require defect layers or nano-materials with strong light absorption. Herein, we propose a novel TPP biosensor by using one-dimensional topological photonic crystal (1D TPhC) as DBR, the working wavelength is 633 nm, where 1D TPhC is composed by two 1D photonic crystals (1D PhCs) with different topological invariants. The strong field confinement of 1D TPhC is employed to improve the light absorption of TPP, and enhance the susceptibility of the biosensor to the analyte. Since TPP is polarization-independent, it has superior sensing performance in both transverse electric (TE) and transverse magnetic (TM) polarization modes. The sensitivity and Figure of Merit (FOM) are 2.6553 × 104 RIU−1 (1.3349 × 104 RIU−1) and 3.1238 × 107 RIU−1deg−1 (6.6745 × 108 RIU−1deg−1) for TM(TE)-polarization mode. The proposed TPP biosensor without defect layer, doesn’t need consider the thickness and position of the sensing medium layer, shows high operational flexibility. Besides, with the protection of the topological edge state, this biosensor has high tolerance to the thickness deviations, which can reduce the requirements on fabrication. It is anticipated that the proposed TPP biosensor has excellent sensing performances, possesses great potentials in environmental monitoring, biological detection, etc.
Over the past decade, the plasmonics of graphene and black phosphorus (BP) were widely recognized as promising media for establishing linear and nonlinear light-matter interactions. Compared to the ...conventional metals, they support significant light-matter interaction of high efficiency and show undispersed optical properties. Furthermore, in contrast to the conventional metals, the plasmonic properties of graphene and BP structure can be tuned by electrical and chemical doping. In this review, a deep attention was paid toward the second- and third-order nonlinear plasmonic modes of graphene and BP. We present a theoretical framework for calculating the lifetime for surface plasmons modes of graphene and BP assisted by the coupled mode theory. The effect of the Fermi energy on the second-order and third-order nonlinear response is studied in detail. We survey the recent advances in nonlinear optics and the applications of graphene and BP-based tunable plasmonic devices such as light modulation devices, switches, biosensors, and other nonlinear photonic devices. Finally, we highlight a few representative current applications of graphene and BP to photonic and optoelectronic devices.
Optical biosensor, which perceptively captures the variety of refractive index (RI) of the surrounding environment, has great potential applications in detecting property changes and types of ...analytes. However, the disequilibrium of light-matter interaction in different polarizations lead to the polarization-dependence and low sensitivity. Here, we propose a polarization-independent and ultrasensitive biosensor by introducing a one-dimensional topological photonic crystal (1D TPhC), where two N-period 1D photonic crystals (PhC1 and PhC2) with different topological invariants are designed for compressing the interaction region of the optical fields, and enhancing the interaction between the light and analyte. Since the strong light-matter interaction caused by the band-inversion is polarization-independent, the biosensor can obtain superior sensing performance both for TE and TM polarization modes. The sensitivity and Figure of Merit (FOM) of the designed biosensor are 1.5677×10
6
RIU
−1
(1.3497 × 10
6
RIU
−1
) and 7.8387×10
10
RIU
−1
deg
−1
(4.4990×10
10
RIU
−1
deg
−1
) for TM (TE) polarization mode, which performs two orders of magnitude enhancement compared with the reported biosensors. With the protection of the topological edge state, this biosensor has high tolerance to the thickness deviations and refractive index (RI) variations of the component materials, which can reduce the requirements on fabrication and working environment. It is anticipated that the proposed biosensor possesses excellent sensing performances, may have great potentials in environmental monitoring, medical detection, etc.
Plasmon Induced Transparency (PIT) effect possesses the characteristics of sharp and pronounced spectral response and considerable group delay. In this work, a PIT system consists of two noncoplanar ...Dirac semimetal particles (DSPs) has been studied by finite-difference time-domain (FDTD) method. Tailoring of this PIT system can be achieved by structural parameters, Fermi energy (EF), refractive index (RI) of dielectric medium and polarization angle of incident light. Benefitted from its smaller particle size, the bandwidth of PIT window in this DSPs system is up to 3.94 THz, which is much broader than in bulk Dirac semimetal PIT system (about 0.36 THz). An efficient second order nonlinearity of this DSPs system is obtained for its intensive localized field, non-centrosymmetric structureunique and unique electromagnetic mode. The second-order nonlinear conversion efficiency in this system is up to 10−6 to 10−5 for its noncoplanar structure. This noncoplanar DSPs system can also achieve approximate linear light intensity modulation effect of its second harmonic waves (SHWs). This developed noncoplanar DSPs structure could provide guidance for the design of high integration Dirac semimetal THz devices.
•A noncoplanar plasmon induced transparent (PIT) system consisting of two Dirac semimetal particles (DSPs) is proposed.•This PIT window is much broader than that in bulk Dirac semimetal PIT systems and can be more flexible for applications in optical communications.•A conclusion is concluded that the second harmonic waves (SHWs) of this PIT system can attain higher conversion efficiency and can be taken as an effective terahertz radiation source.
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